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WO2016145309A1 - Dispositif électronique souple imprimé 3d - Google Patents

Dispositif électronique souple imprimé 3d Download PDF

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Publication number
WO2016145309A1
WO2016145309A1 PCT/US2016/022005 US2016022005W WO2016145309A1 WO 2016145309 A1 WO2016145309 A1 WO 2016145309A1 US 2016022005 W US2016022005 W US 2016022005W WO 2016145309 A1 WO2016145309 A1 WO 2016145309A1
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WO
WIPO (PCT)
Prior art keywords
conductive
printed
thermoplastic elastomer
insulating
electronic device
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/US2016/022005
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English (en)
Inventor
Jennifer A. Lewis
Travis A. BUSBEE
Alexander D. VALENTINE
Johan U. LIND
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Harvard University
Original Assignee
Harvard University
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Filing date
Publication date
Application filed by Harvard University filed Critical Harvard University
Publication of WO2016145309A1 publication Critical patent/WO2016145309A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/54—Inks based on two liquids, one liquid being the ink, the other liquid being a reaction solution, a fixer or a treatment solution for the ink
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y80/00—Products made by additive manufacturing
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/02—Printing inks
    • C09D11/10—Printing inks based on artificial resins
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/30—Inkjet printing inks
    • C09D11/32—Inkjet printing inks characterised by colouring agents
    • C09D11/322—Pigment inks
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D11/00—Inks
    • C09D11/30—Inkjet printing inks
    • C09D11/38—Inkjet printing inks characterised by non-macromolecular additives other than solvents, pigments or dyes
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/0277—Bendability or stretchability details
    • H05K1/0283—Stretchable printed circuits
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/09—Use of materials for the conductive, e.g. metallic pattern
    • H05K1/092—Dispersed materials, e.g. conductive pastes or inks
    • H05K1/095—Dispersed materials, e.g. conductive pastes or inks for polymer thick films, i.e. having a permanent organic polymeric binder
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/02—Details
    • H05K1/03—Use of materials for the substrate
    • H05K1/038—Textiles
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K1/00—Printed circuits
    • H05K1/16—Printed circuits incorporating printed electric components, e.g. printed resistor, capacitor, inductor
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/01—Dielectrics
    • H05K2201/0104—Properties and characteristics in general
    • H05K2201/0129—Thermoplastic polymer, e.g. auto-adhesive layer; Shaping of thermoplastic polymer
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/01—Dielectrics
    • H05K2201/0104—Properties and characteristics in general
    • H05K2201/0133—Elastomeric or compliant polymer
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
    • H05K2201/00—Indexing scheme relating to printed circuits covered by H05K1/00
    • H05K2201/05—Flexible printed circuits [FPCs]
    • H05K2201/051—Rolled

Definitions

  • the present disclosure is related generally to three-dimensional printing (3D) printing and more particularly to 3D printing of multiple materials.
  • stretchable electronics is paving the way for advancements in soft robotics, wearable sensors and flexible displays, among other technologies.
  • building functional soft electronic devices can require integrating soft materials with rigid, wafer-based electronic components.
  • stretchable electronics may be combined with flexible substrates or fabrics that can undergo a wide range of motion. To move beyond prototyping, new materials and fabrication methods may be needed to integrate diverse components together and realize a fully functional soft electronic device. BRIEF SUMMARY
  • a 3D printed conductive structure for a flexible electronic device comprises a plurality of electrically conductive particles at least partially embedded in a thermoplastic elastomer and arranged to define a
  • the 3D printed conductive structure comprises a predetermined geometry and may be supported by a flexible substrate comprising a sheet, textile, adhesive or laminate.
  • An ink formulation for 3D printing a flexible electronic device comprises a thermoplastic elastomer dissolved in a polar solvent.
  • a method of 3D printing a flexible electronic device comprises depositing one or more conductive filaments in a predetermined pattern on a substrate, where the one or more conductive filaments comprise a conductive ink formulation comprising a polar solvent, a thermoplastic elastomer, and a plurality of electrically conductive particles.
  • the polar solvent is evaporated to dry the one or more conductive filaments, thereby forming a 3D printed conductive structure on the substrate.
  • FIG. 1 shows a continuous filament being extruded through a deposition nozzle and deposited on a substrate, where in this example the continuous filament is extruded from a conductive ink formulation that includes a polar solvent, thermoplastic polyurethane (TPU) and silver (Ag) flakes.
  • TPU thermoplastic polyurethane
  • Ag silver
  • FIG. 2 shows the stretchability of the conductive structure formed upon drying the continuous filament of FIG. 1.
  • FIG. 3A shows an exemplary strain gauge and FIG. 3B shows an exemplary multi-electrode array formed by 3D printing. Both conductive structures are printed from an Ag-TPU conductive ink formulation.
  • FIGs. 4A and 4B are schematics of an exemplary 3D printed flexible electronic device, where FIG. 4B shows a close-up view of the mid- portion of FIG. 4A.
  • FIG. 4C provides mechanical data, specifically Young's modulus, for exemplary soft and stiff insulating materials (TPU) and exemplary soft and stiff conductive materials (Ag-TPU).
  • TPU soft and stiff insulating materials
  • Ag-TPU exemplary soft and stiff conductive materials
  • FIGs. 5A-5C show deposition nozzles carrying out pick and place maneuvers with exemplary electronic components.
  • FIGs. 6A-6D show images of an exemplary LED array formed by a combination of 3D printing steps to deposit conductive and insulating filaments on the flexible substrate as well as pick and place maneuvers to place the LEDs and other functional components.
  • FIGs. 7A-7C are plots showing the impact of drying temperature and time on the electrical conductivity of conductive structures printed from ink formulations comprising Ag flakes, TPU and dimethylformamide (DMF).
  • FIGs. 8A-8C show the electrical and mechanical properties of conductive structures, which are 3D printed from ink formulations
  • FIGs. 8D-8F show AR/R 0 and resistance of conductive structures including 36 vol.% Ag as a function of % strain and strain cycle.
  • FIGs. 9A and 9B show the impact of total solids loading on the viscosity and storage modulus of conductive ink formulations including a silver volume fraction of 36 vol.%.
  • FIGs. 10A and 10B show the impact of silver volume fraction on the viscosity and storage modulus of conductive ink formulations including a solids loading of 40%.
  • FIGs. 1 1 A-1 1 D show tape cast conductive structures formed from Ag-TPU and encapsulated in polydimethylsiloxane (PDMS) and the resistance of these structures while being strained.
  • FIGs. 12A and 12B show images of 3D printed electrode arrays for biological stimulation.
  • FIG. 13 shows a 3D printed lab-on-a-chip (heart-on-a-chip) device for sensing cellular mechanical forces.
  • FIGs. 14A-14F show an exemplary process in which 3D printing of insulating and conductive filaments is combined with pick and place maneuvers to build a multi-material flexible electronic device that includes a number of functional components.
  • FIGs. 15A-15B provide data showing how resistance varies as a function of strain and time for a 3D printed conductive structure with and without a strain limiting layer.
  • FIG. 16 shows how resistance in a 3D printed conductive filament can be decreased without sacrificing significant lateral resolution.
  • FIG. 17 shows how increasing the volume fraction of silver particles in a 3D printed conductive filament increases the Young's Modulus of the conductive structure formed after drying.
  • a 3D printed conductive structure for a flexible electronic device comprises a plurality of electrically conductive particles at least partially embedded in a thermoplastic elastomer.
  • the electrically conductive particles form a percolating conductive pathway through the thermoplastic elastomer in both strained and unstrained states.
  • the 3D printed conductive structure may function as, for example, an interconnect, electrode, antenna or a sensor in a flexible electronic device.
  • the 3D printed conductive structure may be combined with a stretchable insulating structure formed by 3D printing or another method to provide electrical isolation and, in some cases, local strain relief.
  • Such flexible electronic devices may exhibit significant free-form stretching and straining while maintaining full electrical function, an extremely useful characteristic when compared to existing products based on rigid printed circuit boards and inflexible wires.
  • the devices may have a mechanical integrity sufficient to withstand linear strains of from greater than 0% to 100% without mechanical breakage.
  • the flexible electronic devices may be designed to be biocompatible. Such devices may find application in electronics, biometric sensing, energy harvesting, implantable stimulation and monitoring, lab-on-a-chip (e.g., heart-on-a-chip) technology, electrocardiograms (ECG/EKGs), wearable healthcare technology, or others.
  • the 3D printed conductive structure has a predetermined geometry that may be determined by the 3D printing process.
  • 3D printing or direct write fabrication is an extrusion-based process that entails flowing an ink formulation having suitable rheological properties through a deposition nozzle, which is moving relative to an underlying substrate. As the deposition nozzle (and/or substrate) is moved in an x-, y-, and/or z-direction, a continuous filament comprising the ink formulation may be extruded through the nozzle and deposited on the substrate in a desired configuration or pattern. 3D structures may be built up layer-by-layer using this approach.
  • the rheology of the ink formulation influences the printability, height, and morphology of structures that can be fabricated.
  • the ink formulation may have a sufficiently high elastic storage modulus, G', and shear yield strength to partially or fully maintain the printed shape.
  • G' elastic storage modulus
  • shear yield strength to partially or fully maintain the printed shape.
  • the ink formulation ideally exhibits significant shear thinning to allow flow through the deposition nozzle without requiring prohibitively high driving pressures.
  • a conductive ink formulation comprising conductive silver flakes, a thermoplastic polyurethane and a polar solvent is extruded to deposit a conductive filament on the substrate.
  • the conductive filament is transformed into a highly stretchable conductive structure, as shown in FIG. 2.
  • 3D printing is carried out at or near room temperature and drying occurs at an elevated temperature after printing to remove the solvent from the ink formulation. It is contemplated that 3D printing may alternatively take place at an elevated temperature at which the ink formulation is in a molten or semi-solid state (e.g., fused filament fabrication (FFF)). In such a case, no solvent is used, and thus the drying step may be replaced with a cooling step to solidify the molten or semi-solid material.
  • FFF fused filament fabrication
  • the predetermined geometry of the 3D printed conductive structure may be a straight and/or curved line defined by the path of the deposition nozzle as the continuous filament is deposited on the substrate. More complex geometries may be formed by depositing one or more of the continuous filaments in any desired two- or three-dimensional pattern that may include one or more layers.
  • FIG. 3A shows an exemplary strain gauge
  • FIG. 3B shows an exemplary multi-electrode array formed by 3D printing a conductive ink formulation comprising silver flakes dispersed in a polar solvent including thermoplastic polyurethane.
  • the predetermined geometry of the 3D printed conductive structure may be selected to minimize or in some cases maximize strain-dependent resistance changes.
  • the 3D printed conductive structure is intended to function as a strain sensor, then it may be beneficial to have a geometry (such as the elongated serpentine pattern of the strain gauge of FIG. 3A) that maximizes strain-dependent resistance changes in a particular direction.
  • a geometry such as the elongated serpentine pattern of the strain gauge of FIG. 3A
  • thermoplastic elastomer may be understood to refer to a polymer, copolymer or a physical mix of polymers that has both
  • thermoplastic and elastomeric (rubber-like) characteristics may exhibit high stretchability at room temperature and may also be processable as a melt at elevated temperatures, in contrast to
  • thermosetting polymers may comprise a thermoplastic polyurethane (TPU), a styrenic block copolymer (TPE-s), a thermoplastic olefin (TPE-o), an elastomeric alloy (e.g., TPE-v or TPV), a thermoplastic copolyester, and/or a thermoplastic polyamide.
  • TPU thermoplastic polyurethane
  • TPE-s styrenic block copolymer
  • TPE-o thermoplastic olefin
  • elastomeric alloy e.g., TPE-v or TPV
  • thermoplastic copolyester e.g., TPV
  • thermoplastic elastomer may be selected to have suitable mechanical properties (e.g., a desired Shore hardness) to impart the desired stiffness or pliability to the printed structure.
  • the thermoplastic elastomer may be a stiff thermoplastic elastomer comprising, in some embodiments, a Shore hardness of greater than 70A, or at least about 80A.
  • the thermoplastic elastomer may be a soft thermoplastic elastomer comprising, in some embodiments, a Shore hardness of 70A or less, 50A or less, or 35A or less.
  • the Shore hardness may be determined according to ASTM Standard D 2240.
  • Thermoplastic polyurethane, or TPU is used in a number of examples described in this disclosure and has been found to be suitable for forming conductive and insulating structures having a range of stiffnesses.
  • Thermoplastic polyurethanes having different values of Shore hardness are available commercially.
  • stiff thermoplastic polyurethanes having Shore hardnesses greater than 70A such as Elastollan® TPU 1 180A, which has a Shore hardness of 80A
  • soft thermoplastic polyurethanes having Shore hardnesses of 70A or less, such as Elastollan ® Soft 35A, which has a Shore hardness of 35A are also commercially available from BASF Corp.
  • the 3D printed conductive structure may be disposed on a substrate which is formed by 3D printing or prefabricated using another method.
  • the substrate may be a flexible substrate comprising a sheet, textile, adhesive or laminate.
  • the substrate may be formed from a polymer, such as polydimethylsiloxane, or a thermoplastic elastomer.
  • the substrate may be formed of woven or unwoven filaments or fibers (e.g., synthetic or natural fibers).
  • the substrate may be a pressure-sensitive adhesive layer suitable for adhering to human skin.
  • the substrate may be a sacrificial substrate that is removed after forming the conductive structure.
  • the substrate may comprise an insulating material and, in some cases, may take the form of the insulating structure described below.
  • the electrically conductive particles of the 3D printed conductive structure may comprise a conductive material such as silver, carbon, nickel, platinum, palladium, aluminum, or another conductive metal or alloy.
  • the electrically conductive particles may be anisotropic so as to align better when a strain is applied to the conductive structure and to mitigate any unwanted resistance change.
  • the conductive particles may take the form of microscale or nanoscale rods, tubes, fibers, wires or flakes (e.g., microtubes or nanotubes, microfibers or nanofibers, nanowires, etc.).
  • the electrically conductive particles may have a particle size in the range of about 1 nm to about 100 microns, and more typically from about 100 nm to about 10 microns.
  • the electrically conductive particles may be present in the conductive structure at a concentration of from about 15 wt.% to about 95 wt.%, where the thermoplastic elastomer accounts for the balance (e.g., from about 5 wt.% to 85 wt.%).
  • the concentration may be from about 50 wt.% to about 95 wt.%.
  • conductive particles comprising carbon a concentration of from about 15 wt.% to about 30 wt.% may be used.
  • the electrically conductive particles may be present at a concentration (with respect to the total volume of thermoplastic elastomer and conductive particles) in the range of from about 20 vol.% to about 60 vol.%.
  • the concentration may also be from about 25 vol.% to about 45 vol.%, or preferably from about 32 vol.% to about 40 vol.%, in order to maximize the electromechanical properties of the 3D printed conductive structure.
  • the concentration of the electrically conductive particles may be at least about 25 vol.%, at least about 30 vol.%, or at least about 35 vol.%.
  • the concentration is no higher than 50 vol.%, no higher than 45 vol.%, or no higher than 40 vol. %.
  • a 3D printed flexible electronic device 400 may comprise the 3D printed conductive structure 402 described above and an insulating structure 404 disposed adjacent to the 3D printed conductive structure 402.
  • the insulating structure 404 may overlie, underlie, and/or encapsulate the 3D printed conductive structure 402, and the insulating structure 404 may or may not be in direct contact with the 3D printed conductive structure 402.
  • the insulating structure 404 may comprise a thermoplastic elastomer which is the same as or different from the thermoplastic elastomer of the 3D printed conductive structure 402.
  • the insulating structure may be electrically insulating and thus may not include electrically conductive particles.
  • the insulating structure 404 may not comprise a thermoplastic elastomer, but rather may comprise another polymer, such as polydimethylsiloxane (PDMS).
  • PDMS polydimethylsiloxane
  • the insulating structure 404 may be formed by 3D printing or another fabrication method.
  • the insulating structure 404 may have any desired geometry, particularly if formed by 3D printing, where a continuous filament comprising a thermoplastic elastomer or another polymer may be deposited on the substrate.
  • the insulating structure 404 may comprise a straight and/or curved line which may be defined by the path of the deposition nozzle. More complex geometries may be formed by depositing one or more of the continuous filaments in any desired two- or three-dimensional pattern that may include one or more layers.
  • the 3D printed conductive structure 402 may have a higher stiffness than the insulating structure 404. This may be due at least in part to the stiffening effect of the electrically conductive particles that impart electrical conductivity to the conductive structure 402, as shown in FIG. 17 for silver particles in a thermoplastic polyurethane. Thus, even if the conductive and insulating structures 402,404 comprise the same
  • the 3D printed conductive structure may exhibit a higher stiffness. Due to the sometimes significant difference in stiffnesses between the conductive and insulating structures 402,404, as revealed by the exemplary data of FIG. 4C, it may be beneficial to include a strain limiting region 406 between the 3D printed conductive structure 402 and the insulating structure 404.
  • the strain limiting region 406 may have a lower stiffness than the 3D printed conductive structure 402 and a higher stiffness than the insulating structure 404, in one embodiment. Referring to FIG.
  • the strain limiting region 406 may have, for example, a stiffness (e.g., Young's Modulus) corresponding to the "stiff TPU," while the 3D printed conductive structure 402 has the stiffness of the "soft AgTPU” and the insulating structure 404 has the stiffness of the "soft TPU.”
  • the strain limiting region 406 may help to prevent unintended strains from being transmitted to the 3D printed conductive structure 402 during flexing or deformation of the flexible electronic device 400.
  • the strain limiting region 406 may comprise a thermoplastic elastomer having a Shore hardness higher than that of the thermoplastic elastomer of the insulating structure 404.
  • the thermoplastic elastomer of the strain limiting region 406 may be a stiff thermoplastic polyurethane having a Shore hardness greater than 70A, while the thermoplastic elastomer of the insulating structure may be a soft thermoplastic polyurethane having a Shore hardness of 70A or less.
  • the Shore hardness of the stiff thermoplastic polyurethane may be at least about 80A and the Shore hardness of the soft thermoplastic polyurethane may be about 50A or less.
  • the strain limiting region 406 may also be electrically insulating, and thus may be referred to as an insulating strain limiting region 406. [0041] It is also possible that - despite the stiffening effect of the electrically conductive particles - the 3D printed conductive structure 402 may have a lower stiffness than the insulating structure 404. For example, the 3D printed conductive structure 402 may be fabricated from a
  • thermoplastic elastomer having a much lower Shore hardness than the insulating structure 404, thereby offsetting the stiffening effect of the conductive particles.
  • the conductive structure 402 may have a higher stiffness than the 3D printed conductive structure but a lower stiffness than the insulating structure 404, and thus the strain limiting region 406 may serve to limit the strain
  • the strain limiting region 406 may thus comprise a thermoplastic elastomer having a Shore hardness lower than that of the thermoplastic elastomer of the insulating structure 404.
  • the strain limiting region 406 may have a stiffness that is the same as that of either the 3D printed conductive structure 402 or the insulating structure 404. It is also contemplated that the strain limiting region 406 may have a graded stiffness, where the stiffness increases or decreases (e.g., linearly, stepwise, exponentially or in another fashion) across the strain limiting region 406 from the 3D printed conductive structure 402 to the insulating structure 404. Such a graded structure of the strain limiting region 406 may be obtained by 3D printing adjacent filaments formed from thermoplastic elastomers having different Shore hardnesses.
  • the strain limiting region 406 may be formed by 3D printing and may have any desired 3D-printable geometry.
  • the predetermined geometry of the strain limiting region may be as described above for the insulating structure and/or the 3D printed conductive structure.
  • the geometry of the strain limiting region 406 is determined by the geometry of the 3D printed conductive structure 402 since the strain limiting region 406 may be positioned directly adjacent thereto.
  • the benefit of printing a stiffer ink formulation along the print path of a softer conductive ink formulation in terms of the impact on the electrical resistance of the conductive structure may be understood in reference to FIGs. 15A and 15B, which are described in the Examples below.
  • the 3D printed flexible electronic device may further comprise a plurality (two or more) of the 3D printed conductive structures, where each conductive structure may be formed by 3D printing to have a desired geometry and position.
  • the 3D printed flexible electronic device may comprise an array of electrodes, where each electrode has a position optimized for electrical stimulation of a specific region of an individual.
  • Each of the 3D printed conductive structures comprises a plurality of electrically conductive particles at least partially embedded in an electrically insulating material comprising a thermoplastic elastomer, as described above.
  • An insulating structure may be adjacent to each 3D printed conductive structure, and in some or all cases a strain limiting region may be disposed between the insulating structure and the 3D printed conductive structure, also as described above.
  • the 3D printed flexible electronic device 400 may further include a functional component 410, such as the LED 408 shown in FIGs. 4A and 4B, electrically connected to the 3D printed conductive structure 402.
  • the functional component 410 may be an active electronic component, a passive electronic component, an optoelectronic component, an
  • the functional component 410 may be prefabricated and incorporated into the flexible electronic device 400 using a pick and place maneuver, as described below. It is also contemplated that the functional component 410 may be formed by 3D printing during fabrication of the flexible electronic device 400.
  • the functional component 410 may be a rigid component with a significantly higher stiffness than that of the 3D printed conductive structure 402, it may be beneficial to include a strain limiting region 412 between the functional component 410 and the 3D printed conductive structure 402.
  • the strain limiting region 412 may have a higher stiffness than the 3D printed conductive structure 402 and a lower stiffness than the functional component 410.
  • the strain limiting region 412 may have a stiffness that is the same as that of the 3D printed conductive structure 402. Due to its placement between the functional component 410 and the 3D printed conductive structure 402, the strain limiting region 412 may be electrically conductive so as to provide an electrical path between the two, and thus may be referred to as a conductive strain limiting region 412.
  • the conductive strain limiting region 412 may have, in one example, a stiffness corresponding to the "stiff AgTPU," while the 3D printed conductive structure 402 has the stiffness of the "soft AgTPU.”
  • the conductive strain limiting region 412 may comprise a thermoplastic elastomer having a higher Shore hardness than the
  • the thermoplastic elastomer of the conductive strain limiting region 412 may be a stiff thermoplastic polyurethane having a Shore hardness of greater than 70A, or at least about 80A
  • the thermoplastic elastomer of the 3D printed conductive structure 402 may be a thermoplastic
  • the conductive strain limiting region 412 may include electrically conductive particles at least partially embedded in the thermoplastic elastomer and arranged to define a percolating conductive pathway through some or all of the conductive strain limiting region 412, thereby imparting the desired electrical conductivity.
  • the conductive strain limiting region 412 may be formed by 3D printing and may have any desired 3D-printable geometry.
  • the predetermined geometry of the conductive strain limiting region 412 may be as described above for the insulating structure and/or the 3D printed conductive structure. It is also contemplated that the conductive strain limiting region 412 may have a graded stiffness, where the stiffness increases or decreases (e.g., linearly, stepwise, exponentially or in another fashion) across the strain limiting region 412 from the 3D printed conductive structure 402 to the functional component 410. Such a graded structure of the strain limiting region 412 may be obtained by 3D printing adjacent filaments formed from
  • thermoplastic elastomers having different Shore hardnesses and/or different amounts of conductive particles.
  • a suitable ink formulation having a rheology suitable for 3D printing of flexible electronic devices.
  • Arriving at a suitable ink formulation is a challenge due to the various processing and property requirements of 3D printed conductive and insulating structures.
  • a solvent that can effectively dissolve a thermoplastic elastomer while still remaining volatile for post-deposition evaporation may be required for printing.
  • an ideal ink formulation is engineered to dry quickly without sacrificing the aesthetics (e.g., transparency) and integrity (e.g., edge continuity) of the printed structure.
  • the conductive ink formulations may have additional requirements, such as exhibiting both a high conductivity and high stretchability, as well as enduring high strains without electrical breakdown or mechanical failure. Also important is minimizing the change in resistance of the 3D printed conductive structure as a function of strain cycle, which may be referred to as cyclic AR/R 0 .
  • the ink formulation may comprise a thermoplastic elastomer dissolved in a polar solvent.
  • the ink formulation may be a conductive ink formulation that further includes a plurality of electrically conductive particles and, in some cases, a surfactant or dispersing agent to improve the dispersion of the conductive particles.
  • a suitable surfactant or dispersing agent may comprise, for example, a long chain fatty acid with a carboxylic acid head.
  • the ink formulation may alternatively be an insulating ink formulation that does not include the electrically conductive particles.
  • the electrically conductive particles may comprise a conductive material selected from among gold, silver, carbon, nickel, platinum, palladium, aluminum, and other conductive metals and/or alloys, as described above.
  • the electrically conductive particles may be anisotropic so as to align better under an applied strain and mitigate any unwanted resistance change.
  • anisotropic particles may undergo alignment during 3D printing, as described for example in International Patent
  • the conductive particles may take the form of microscale or nanoscale rods, tubes, fibers, wires or flakes (e.g., microtubes or nanotubes, microfibers or nanofibers, nanowires, etc.).
  • the electrically conductive particles may have a particle size in the range of about 1 nm to about 100 microns, and more typically from about 100 nm to about 10 microns.
  • the thermoplastic elastomer may have any of the characteristics described above and may comprise a thermoplastic polyurethane (TPU), a styrenic block copolymer (TPE-s), a thermoplastic olefin (TPE-o), an elastomeric alloy (e.g., TPE-v or TPV), a thermoplastic copolyester, and/or a thermoplastic polyamide.
  • the thermoplastic elastomer may be a stiff thermoplastic elastomer comprising, in some embodiments, a Shore hardness of greater than 70A, or at least about 80A.
  • the thermoplastic elastomer may be a soft thermoplastic elastomer comprising, in some embodiments, a Shore hardness of about 70A or less, or about 50A or less.
  • the polar solvent may comprise one or more of the following: dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), dimethylformamide (DMF), dibasic ester (DBE), N-methyl-2-pyrrolidone (NMP), alkyl ester, dichloromethane, glycol ether, glycol ether acetate and water (H 2 O).
  • DMSO dimethyl sulfoxide
  • THF dimethylformamide
  • DBE dibasic ester
  • NMP N-methyl-2-pyrrolidone
  • alkyl ester dichloromethane
  • glycol ether glycol ether acetate and water
  • H 2 O water
  • the polar solvent may include two of the above polar solvents, such as DMF and THF.
  • the volume ratio of the two polar solvents e.g., DMF to THF
  • the ink formulation may further include one or more rheological modifiers, such as one or more of the following: fumed silica, surface functionalized treated fumed silica, associative thickeners, and non- associative thickeners.
  • rheological modifiers such as one or more of the following: fumed silica, surface functionalized treated fumed silica, associative thickeners, and non- associative thickeners.
  • An exemplary associative thickener that may be suitable for the ink formulation comprises a hydrophobically modified ethoxylated urethane resin (HEUR).
  • HEUR hydrophobically modified ethoxylated urethane resin
  • a total solids loading in the ink formulation is from about 15% to about 50% by volume.
  • a method of 3D printing a flexible electronic device comprises depositing one or more conductive filaments in a predetermined pattern on a substrate to form a 3D printed conductive structure.
  • Each conductive filament may be extruded as a continuous filament from a deposition nozzle moving relative to the substrate, as shown in FIG. 1 .
  • the one or more conductive filaments comprise a conductive ink formulation including a polar solvent, a thermoplastic elastomer, a plurality of electrically conductive particles, and optionally a surfactant or dispersant.
  • the thermoplastic elastomer may be a soft thermoplastic elastomer (e.g., TPU) as described above having a Shore hardness of about 70A or less, and thus the conductive ink formulation may be referred to as a soft conductive ink formulation, and the one or more conductive filaments may be referred to as one or more soft conductive filaments.
  • the polar solvent may be evaporated to dry the conductive filament(s) and form a 3D printed conductive structure.
  • the 3D printed conductive structure can be both mechanically and electrically tuned by varying the concentration and type(s) of electrically conductive particles in the conductive ink formulation.
  • the conductive ink formulation may be engineered for high sensitivity to low strains for sensor applications, for high robustness and low sensitivity to strain for wiring applications, and for high biocompatibility for biometric sensing applications.
  • thermoplastic elastomer may also influence the mechanical properties of the conductive structure.
  • the method may further comprise depositing one or more insulating filaments in a predetermined pattern on the substrate to form an insulating structure adjacent to and/or in contact with the conductive structure.
  • Each insulating filament may be extruded as a continuous filament from a deposition nozzle moving relative to the substrate.
  • the deposition nozzle may be the same as or different from the deposition nozzle used for depositing the conductive filament(s), and the deposition of the insulating and conductive filaments may be carried out in serial or in parallel.
  • the one or more insulating filaments may comprise an insulating ink formulation including a thermoplastic elastomer and a polar solvent.
  • the thermoplastic elastomer may be a soft thermoplastic elastomer (e.g., TPU) as described above having a Shore hardness of about 70A or less, and thus the insulating ink formulation may be referred to as a soft insulating ink formulation, and the one or more insulating filaments may be referred to as one or more soft insulating filaments.
  • the polar solvent may be evaporated to dry the insulating filament(s) and form an insulating structure.
  • the properties of the insulating structure which may function as an effective packaging, encapsulating, supporting and/or strain limiting material, may be controlled by varying the concentration and/or
  • the conductive and/or insulating filaments may be heated to a temperature in the range of about 50°C to about 135°C. Typically, the heating is carried out for a time period ranging from about 30 minutes to about 3 hours.
  • the substrate may be a flexible substrate comprising a sheet, textile, adhesive or laminate.
  • the substrate may be formed from a polymer, such as polydimethylsiloxane, or a thermoplastic elastomer.
  • the substrate may be formed of woven or unwoven filaments or fibers (e.g., synthetic or natural fibers).
  • the substrate may be a pressure-sensitive adhesive layer suitable for adhering to human skin.
  • the substrate may be a sacrificial substrate that is removed after forming the conductive structure.
  • the substrate may comprise an insulating material and may serve as one of the insulating structures.
  • the method may further comprise electrically connecting a functional electronic component to the 3D printed conductive structure by a manual or automated pick and place maneuver.
  • the pick and place maneuver may be carried out using the same deposition nozzle employed for 3D printing by generating a vacuum instead of a positive pressure in the nozzle.
  • the vacuum is selected to be strong enough to counteract gravitational forces on small electronic components, such as resistors and LEDs, allowing them to be readily picked up, transported to the desired location, and placed on the substrate.
  • FIGs. 5A-5C show deposition nozzles carrying out pick and place maneuvers with exemplary electronic components.
  • the pick and place maneuver may be carried out before, during and/or after the one or more conductive filaments is deposited, and multiple pick and place maneuvers may be carried out to place a number of electronic components on the substrate.
  • FIGs. 6A-6D show images of an exemplary LED array formed by a combination of 3D printing steps to deposit conductive and insulating filaments on the flexible substrate as well as pick and place maneuvers to place the LEDs and other functional components.
  • the one or more insulating filaments may be deposited before, during or after the functional component is manually or automatically picked and placed.
  • the one or more conductive filaments may comprise one or more soft conductive filaments extruded from a conductive ink formulation comprising a soft thermoplastic elastomer.
  • the one or more insulating filaments may comprise one or more soft insulating filaments extruded from an insulating ink formulation comprising a soft thermoplastic elastomer (which may be the same as or different from that of the soft conductive filament(s)).
  • the method may further entail depositing one or more stiff insulating filaments in a predetermined pattern on the substrate in contact with the one or more soft conductive filaments, so as to form, after drying, a strain limiting structure (or, more specifically, an insulating strain limiting structure) on the substrate.
  • the stiffness of the strain limiting structure may have a stiffness that lies between that of the conductive structure and the insulating structure.
  • the one or more stiff insulating filaments may comprise a stiff insulating ink formulation including a stiff thermoplastic elastomer and a polar solvent, where the stiff thermoplastic elastomer of the stiff insulating ink formulation comprises a higher Shore hardness than the soft
  • the one or more stiff insulating filaments may alternatively have a higher Shore hardness than the soft thermoplastic elastomer of the soft conductive ink formulation used to form the conductive structure.
  • evaporating the polar solvent may comprise drying the one or more stiff insulating filaments, thereby forming the insulating strain limiting structure on the substrate between the 3D printed conductive structure and the insulating structure. The evaporation of the polar solvent may be carried out as described above.
  • the method may further comprise depositing one or more stiff conductive filaments in a predetermined pattern on the substrate in contact with the functional component, so as to form, after drying, a strain limiting structure (or, more specifically, a conductive strain limiting structure) on the substrate.
  • the one or more stiff conductive filaments may comprise a stiff conductive ink formulation comprising a polar solvent, a stiff thermoplastic elastomer, and a plurality of electrically conductive particles, where the stiff thermoplastic elastomer of the stiff conductive ink formulation comprises a higher Shore hardness than the soft thermoplastic elastomer of the soft conductive ink formulation, which is used to form the 3D printed conductive structure.
  • evaporating the polar solvent may comprise drying the one or more stiff conductive filaments, thereby forming the conductive strain limiting structure on the substrate between the functional component and the 3D printed conductive structure.
  • the evaporation of the polar solvent may be carried out as described above.
  • Each of the above-described continuous filaments may be extruded from a conductive or insulating ink formulation that comprises a thermoplastic elastomer (e.g., thermoplastic polyurethane) having the desired hardness or softness in order to produce a conductive or insulating component, or strain limiting region, having the desired stiffness.
  • the soft or stiff insulating filaments may be deposited before, during and/or after the soft or stiff conductive filaments are deposited. Also, any of the above-described filaments may be deposited directly on the substrate or on a previously- deposited filament or portion of a filament.
  • a single deposition nozzle is shown in FIG. 1
  • a plurality of deposition nozzles may be employed for 3D printing.
  • two or more, three or more, four or more, five or more and up to N nozzles may be used for extruding the filaments, where 1 ⁇ N ⁇ 1024; more typically, N is no more than 512, no more than 256, no more than 128, or no more than 64.
  • the conductive and insulating filaments may be extruded from the N nozzles sequentially in a serial deposition process or simultaneously in a parallel deposition process, and each nozzle may contain the same or a different ink. It is also contemplated that the deposition may include both parallel and serial deposition steps. To facilitate sequential or serial printing, the nozzles can be independently controlled in the z-direction.
  • Each nozzle may have an inner diameter of from about 10 microns to about 1 mm in size, and more typically from about 50 microns to about 500 microns.
  • the size of the nozzle may be selected depending on the desired continuous filament diameter.
  • the filament may have a diameter ranging from about 10 microns to about 10 mm, and more typically from about 100 microns (0.1 mm) to about 1 mm.
  • the nozzles may be moved and the filaments may be deposited at print speeds as high as about 3 m/s (e.g., from about 1 cm/s to about 3 m/s), and are more typically in the range of from about 1 mm/s to about 500 mm/s, from about 0.1 mm/s to about 100 mm/s, or from about 0.5 mm/s to about 10 mm/s.
  • 3 m/s e.g., from about 1 cm/s to about 3 m/s
  • the filaments may be deposited at print speeds as high as about 3 m/s (e.g., from about 1 cm/s to about 3 m/s), and are more typically in the range of from about 1 mm/s to about 500 mm/s, from about 0.1 mm/s to about 100 mm/s, or from about 0.5 mm/s to about 10 mm/s.
  • the inks fed to the one or more nozzles may be housed in separate syringe barrels that may be individually connected to a nozzle for printing by way of a Luer-LokTM or other connector.
  • the extrusion of each of the continuous filaments may take place under an applied or injection pressure of from about 1 psi to about 1000 psi, from about 10 psi to about 500 psi, or from about 20 psi to about 100 psi.
  • the pressure during extrusion may be constant or it may be varied.
  • pressures of higher than 100 psi and/or less than 1 psi, for example, may be applied during printing.
  • a variable pressure may yield a continuous filament having a diameter that varies along the length of the filament.
  • the extrusion is typically carried out at ambient or room
  • the nozzle may be moved with respect to the substrate along a
  • predetermined 2D or 3D pathway e.g., from (x-i , y- ⁇ , z-i) to (x 2 , y 2 , z 2 )
  • a positional accuracy of within ⁇ 200 microns, within ⁇ 100 microns, within ⁇ 50 microns, within ⁇ 10 microns, or within ⁇ 1 micron.
  • continuous filaments may be deposited on the substrate with a positional accuracy of within ⁇ 200 microns, within ⁇ 100 microns, within ⁇ 50 microns, within ⁇ 10 microns, or within ⁇ 1 micron.
  • the ink formulations described above but without the polar solvent may be employed in a 3D printing process carried out at an elevated temperature.
  • the thermoplastic elastomer may be heated to a molten or semi-solid state for deposition of the one or more conductive filaments and the one or more insulating filaments in a process that may be referred to as fused filament fabrication (FFF).
  • FFF fused filament fabrication
  • the drying step described above may in this case be replaced with a cooling step to solidify the molten or semi-solid material.
  • Stiff and soft insulating ink formulations are fabricated using thermoplastic polyurethanes of different Shore hardness values dissolved in two polar solvents combined in various ratios.
  • the two polar solvents are N- N-dimethylformamide (DMF), which has a boiling point of 153°C and a vapor pressure of 3.9 Torr, and tetrahydrofuran (THF), which has a boiling point of 66°C and a vapor pressure of 3.9 Torr.
  • the stiff ink formulation includes Elastollan 1 180A, and the soft ink formulation includes Elastollan Soft 35A.
  • the ratios of DMF to THF range from 100:0 to 0:100 in terms of volume.
  • 3D printing is carried out using a deposition nozzle having an inner diameter of 410 microns at a height above the substrate of 0.4 mm, a print speed of 17 mm/s, and a constant pressure of 18 psi.
  • Insulating structures e.g., simple meanders and continuous films
  • extent of drying e.g., wetness or tackiness of structures
  • transparency e.g., edge continuity
  • presence of bubbles e.g., bubbles. All of the observations are made at 5 minutes post-printing. The results are summarized in Table 1 below, and show that an ideal ratio of DMF:THF may be 20:80 for insulating ink formulations comprising either soft or stiff TPU.
  • polyurethane (Elastollan Soft 35A) dissolved in DMF and including various volume fractions of silver flakes are mixed using a planetary mixer.
  • the silver flakes have a particle size of 2-4 ⁇ (Inframat Corp.) and are incorporated into the conductive ink formulations in the following amounts: 15, 18, 21 , 24, 27, 30, 33, 36, 39, 42 and 45 vol.%.
  • Continuous filaments having a linear geometry are 3D printed from the conductive ink formulations and then heated at 50°C for 2 hours to evaporate the solvent prior to electrical testing.
  • the cross-sectional area of the resulting conductive structures is measured with a profilometer and the conductivity is determined by a four-point probe measurement.
  • Conductive structures having a dogbone geometry (gauge length of 1.5 cm) suitable for mechanical testing are formed by tape casting the conductive ink formulations, followed by heating at 50°C for 2 hours to evaporate the solvent. Mechanical tests are carried out on an Instron testing system. Strain to failure (or stretchability) and electrical failure are evaluated using a displacement rate of 0.1 mm/s (strain rate of 0.00667 s "1 ).
  • FIGs. 8A-8C show the electrical and mechanical properties of the conductive structures as a function of silver volume fraction. It is desirable to maximize conductivity, stretchability and the strain to percolation breakdown (or strain to electrical failure), while minimizing cyclic AR/R 0 . By comparing the relationships shown in these figures, an optimal loading of about 36 vol. % silver is identified. In FIGs. 8D-8F, AR/R 0 and resistance are examined as a function of % strain and strain cycle, respectively, for conductive structures including 36 vol.% Ag.
  • Conductive ink formulations comprising silver flakes dispersed in thermoplastic polyurethane (Ag-TPU) and carbon particles (carbon black) dispersed in thermoplastic polyurethane (CB-TPU) are prepared and used to fabricate flexible electronic devices.
  • Dimethylformamide (DMF) is employed as the solvent for both ink formulations.
  • the Ag-TPU formulation includes DMF and 33 wt.% TPU
  • Electrollan Soft 35A dissolved in the solvent.
  • Silver flakes having a particle size of about 2-5 microns are included in the formulation at a concentration of 85 wt.% (with respect to the TPU). All components are mixed together using a planetary mixer.
  • Conductive structures having linear, serpentine and other geometries are prepared by a molding technique using stencils. A resistivity of 5.72 x 10 ⁇ 5 ⁇ -cm, which is equivalent to approximately 3% of the conductivity of bulk silver, and a conductivity of 1 .75 x 10 4 S/cm are measured for the conductive structures.
  • the CB-TPU formulation includes DMF and 33 wt.% TPU
  • FIGs. 1 1 A-1 1 D stenciled conductive structures formed from Ag-TPU are encapsulated in PDMS and strained while the resistance is monitored.
  • the conductive structure of FIG. 1 1 B has a linear geometry and the conductive structure of FIG. 1 1 D has a serpentine geometry.
  • the resistance of the linear conductive structure changes by approximately 10-fold during a 20% strain, but then returns to its baseline resistance without breaking. This demonstrates the robustness of the conductive structures to high strains, as well as their potential use as strain sensors.
  • the conductive structure printed in the serpentine pattern exhibits a small change in resistance, from 1.84 ohms to 1.91 ohms, over the course of one hundred 20% strain cycles, which demonstrates the potential of the conductive structures for use as interconnects in a flexible electronic device.
  • the Ag-TPU conductive ink formulation is also employed to 3D print an electrode array for biological stimulation applications, as shown in FIGs. 12A and 12B.
  • Ag-TPU is printed with TPU in patterned layers, which are then encapsulated in PDMS to make a robust three-dimensional electrode device with embedded wiring.
  • a lab-on-a-chip device for sensing cellular mechanical forces is fabricated by 3D printing.
  • Conductive structures comprising CB-TPU are printed and encapsulated in TPU to form thin cantilever beams onto which cells can adhere, reorganize, and apply mechanical forces.
  • the cellular mechanical forces strain the cantilever beams, which induces a change in resistance measureable through 3D printed electrodes fabricated from a conductive silver ink.
  • the end result is a functional, 8-layer, multi-material device.
  • FIG. 14A shows 3D printing of an insulating structure or matrix comprising a thermoplastic polyurethane
  • FIG. 14B shows 3D printing of a soft conductive ink formulation comprising Ag-TPU on the insulating matrix and also the creation of voids for LEDs
  • FIG. 14C shows a pick and place maneuver to deposit an LED within one of the voids
  • FIG. 14D shows 3D printing of a stiffer conductive ink formulation along the path of the soft conductive ink formulation to form a stiff conductive structure adjacent to a soft conductive structure;
  • FIG. 14E shows the placement of a magnet in predetermined regions of the circuit using a pick and place maneuver; and
  • FIG. 14F shows the final functioning flexible electronic device.
  • FIGs. 15A and 15B show how the resistance of a conductive structure comprising Ag-TPU changes as a function of strain and time, respectively, with and without a strain-limiting layer comprising stiff TPU adjacent to the conductive structure.
  • the resistance of the conductive structure exhibits a much higher stability as a function of strain for a single strain cycle and as a function of time for successive applications of higher strains.
  • the data show that the strain experienced by the conductive structure is reduced with the strain-limiting layer.
  • FIG. 16 shows a plot of resistance as a function of the number of layers deposited to form a 3D printed conductive structure, which in this example is a conductive trace.
  • the inset images show cross-sectional views of the conductive trace having a varying number of layers.
  • the data in FIG. 16 reveal that electrical resistance decreases as the number of layers increases.
  • FIG. 17 shows how the volume fraction of conductive particles (silver flakes in this example) influence the Young's Modulus of the 3D printed conductive structure.

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Abstract

L'invention concerne un procédé d'impression 3D d'un dispositif électronique souple, qui comprend le dépôt d'un ou plusieurs filaments conducteurs dans un motif prédéterminé sur un substrat, lesdits filaments conducteurs comprenant une formulation d'encre conductrice comprenant un solvant polaire, un élastomère thermoplastique et une pluralité de particules électroconductrices. Le solvant polaire est évaporé pour sécher lesdits filaments conducteurs, en formant ainsi une structure conductrice imprimée 3D sur le substrat.
PCT/US2016/022005 2015-03-11 2016-03-11 Dispositif électronique souple imprimé 3d Ceased WO2016145309A1 (fr)

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Cited By (25)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106700736A (zh) * 2016-12-16 2017-05-24 查本谦 一种复合型导电油墨的制备工艺及复合型导电油墨
WO2017127708A1 (fr) * 2016-01-22 2017-07-27 Voxel8, Inc. Dispersions à base d'eau composites imprimables en 3d
WO2018085258A1 (fr) * 2016-11-07 2018-05-11 E. I. Du Pont De Nemours And Company Articles et substrats assurant des performances améliorées d'électronique imprimable
EP3358674A1 (fr) * 2017-02-01 2018-08-08 Astra Gesellschaft Für Asset Management MbH&Co. Kg Dispositif d'antenne souple
CN109014208A (zh) * 2018-09-21 2018-12-18 北京梦之墨科技有限公司 一种液态金属打印机
FR3075313A1 (fr) * 2017-12-18 2019-06-21 Blachere Illumination Procede et systeme de fabrication d'un decor lumineux
EP3505336A1 (fr) 2017-12-20 2019-07-03 The Goodyear Tire & Rubber Company Article comprenant un composant électronique et son procédé de fabrication
US20190300741A1 (en) * 2018-04-03 2019-10-03 Massachusetts Institute Of Technology 3-d printed devices formed with conductive inks and method of making
CN110868815A (zh) * 2019-11-15 2020-03-06 航天恒星科技有限公司 一种曲面立体电路板制备方法及曲面立体电路板
CN110907501A (zh) * 2019-12-10 2020-03-24 新余学院 一种应变不敏感的柔性可拉伸温度/湿度传感器及其制备方法
CN111154253A (zh) * 2019-11-20 2020-05-15 江苏集萃先进高分子材料研究所有限公司 一种用于选择性激光烧结3d打印的压电聚氨酯粉体材料
EP3708619A1 (fr) * 2019-03-11 2020-09-16 Karlsruher Institut für Technologie Encre imprimable et très conductrice pour électronique souple hautement étirable et conducteurs très conducteurs et ultra-étirables ainsi obtenus
JP2020155608A (ja) * 2019-03-20 2020-09-24 大日本印刷株式会社 配線基板及び配線基板の製造方法
CN111909569A (zh) * 2019-05-07 2020-11-10 施乐公司 导电油墨组合物和由其制成的制品
US10851251B2 (en) 2015-11-03 2020-12-01 Massachusetts Institute Of Technology Block copolymer ink formulation for 3D printing and method of making a 3D printed radiofrequency (RF) device
EP3589353A4 (fr) * 2017-03-02 2020-12-16 Saluda Medical Pty Limited Conducteur imprimé
US10935466B2 (en) 2017-12-20 2021-03-02 The Goodyear Tire & Rubber Company Integrated tire sensor and reader system
US20210213677A1 (en) * 2017-07-28 2021-07-15 Hewlett-Packard Development Company, L.P. Printing tamper evident security structures
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US11320323B2 (en) 2017-09-06 2022-05-03 Regents Of The University Of Minnesota Additively manufactured flexible electronic sensors and conductive compositions used therein
WO2022180577A1 (fr) * 2021-02-24 2022-09-01 Universidade De Coimbra Circuit imprimé souple, encre et procédé d'obtention d'un circuit imprimé souple de celui-ci
CN116884668A (zh) * 2023-06-30 2023-10-13 芯体素(杭州)科技发展有限公司 适用于3d打印弹性探针的导电弹性银浆及其制备方法与应用
US11845219B2 (en) 2019-05-06 2023-12-19 Massachusetts Institute Of Technology 3-d printed devices formed with magnetic inks and methods of making graded index structures
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US12427714B2 (en) 2018-10-19 2025-09-30 National Research Council Of Canada Functionalized product fabricated from a resin comprising a functional component and a polymeric resin, and method of making the same

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20010036718A1 (en) * 2000-02-24 2001-11-01 Williams Vernon M. Stereolithographically fabricated conductive elements, semiconductor device components and assemblies including such conductive elements, and methods
US20100007692A1 (en) * 2006-12-21 2010-01-14 Agfa Graphics Nv 3d-inkjet printing methods
US20130320467A1 (en) * 2010-12-08 2013-12-05 Condalign As Method for assembling conductive particles into conductive pathways and sensors thus formed
WO2014113937A1 (fr) * 2013-01-23 2014-07-31 Henkel IP & Holding GmbH Encre conductrice souple

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20010036718A1 (en) * 2000-02-24 2001-11-01 Williams Vernon M. Stereolithographically fabricated conductive elements, semiconductor device components and assemblies including such conductive elements, and methods
US20100007692A1 (en) * 2006-12-21 2010-01-14 Agfa Graphics Nv 3d-inkjet printing methods
US20130320467A1 (en) * 2010-12-08 2013-12-05 Condalign As Method for assembling conductive particles into conductive pathways and sensors thus formed
WO2014113937A1 (fr) * 2013-01-23 2014-07-31 Henkel IP & Holding GmbH Encre conductrice souple

Cited By (46)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10851251B2 (en) 2015-11-03 2020-12-01 Massachusetts Institute Of Technology Block copolymer ink formulation for 3D printing and method of making a 3D printed radiofrequency (RF) device
WO2017127708A1 (fr) * 2016-01-22 2017-07-27 Voxel8, Inc. Dispersions à base d'eau composites imprimables en 3d
US20170253751A1 (en) * 2016-01-22 2017-09-07 Voxel8, Inc. 3d printable composite waterborne dispersions
CN110325572A (zh) * 2016-11-07 2019-10-11 E.I.内穆尔杜邦公司 提供可印刷电子器件的改进的性能的制品以及基材
WO2018085258A1 (fr) * 2016-11-07 2018-05-11 E. I. Du Pont De Nemours And Company Articles et substrats assurant des performances améliorées d'électronique imprimable
US10827610B2 (en) 2016-11-07 2020-11-03 E I Du Pont De Nemours And Company Articles and substrates providing improved performance of printable electronics
JP2019536267A (ja) * 2016-11-07 2019-12-12 イー・アイ・デュポン・ドウ・ヌムール・アンド・カンパニーＥ．Ｉ．Ｄｕ Ｐｏｎｔ Ｄｅ Ｎｅｍｏｕｒｓ Ａｎｄ Ｃｏｍｐａｎｙ 印刷可能なエレクトロニクスの性能を向上させる物品及び基材
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EP3358674A1 (fr) * 2017-02-01 2018-08-08 Astra Gesellschaft Für Asset Management MbH&Co. Kg Dispositif d'antenne souple
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US20210213677A1 (en) * 2017-07-28 2021-07-15 Hewlett-Packard Development Company, L.P. Printing tamper evident security structures
US11623388B2 (en) * 2017-07-28 2023-04-11 Hewlett-Packard Development Company, L.P. Additive manufacturing methods for printing tamper evident security structures with horizontal and vertical serpentine patterns
US11320323B2 (en) 2017-09-06 2022-05-03 Regents Of The University Of Minnesota Additively manufactured flexible electronic sensors and conductive compositions used therein
FR3075314A1 (fr) * 2017-12-18 2019-06-21 Blachere Illumination Procede et systeme pour la fabrication d'un decor lumineux
FR3075313A1 (fr) * 2017-12-18 2019-06-21 Blachere Illumination Procede et systeme de fabrication d'un decor lumineux
US10792960B2 (en) 2017-12-20 2020-10-06 The Goodyear Tire & Rubber Company Article with electronic component inclusion
EP3505336A1 (fr) 2017-12-20 2019-07-03 The Goodyear Tire & Rubber Company Article comprenant un composant électronique et son procédé de fabrication
US10935466B2 (en) 2017-12-20 2021-03-02 The Goodyear Tire & Rubber Company Integrated tire sensor and reader system
US11267981B2 (en) 2018-04-03 2022-03-08 Massachusetts Institute Of Technology 3-D printed devices formed with conductive inks and method of making
US20190300741A1 (en) * 2018-04-03 2019-10-03 Massachusetts Institute Of Technology 3-d printed devices formed with conductive inks and method of making
CN109014208B (zh) * 2018-09-21 2023-06-30 北京梦之墨科技有限公司 一种液态金属打印机
CN109014208A (zh) * 2018-09-21 2018-12-18 北京梦之墨科技有限公司 一种液态金属打印机
US12427714B2 (en) 2018-10-19 2025-09-30 National Research Council Of Canada Functionalized product fabricated from a resin comprising a functional component and a polymeric resin, and method of making the same
EP3708619A1 (fr) * 2019-03-11 2020-09-16 Karlsruher Institut für Technologie Encre imprimable et très conductrice pour électronique souple hautement étirable et conducteurs très conducteurs et ultra-étirables ainsi obtenus
CN113498427A (zh) * 2019-03-11 2021-10-12 卡尔斯鲁厄技术研究所 用于高度可拉伸的软电子器件的高传导性可印刷油墨及可由其获得的高传导性超可拉伸导体
US20220049119A1 (en) * 2019-03-11 2022-02-17 Karlsruher Institut für Technologie Highly conductive, printable ink for highly stretchable soft electronics and highly conductive, ultra-stretchable conductors obtainable therefrom
WO2020182408A1 (fr) * 2019-03-11 2020-09-17 Karlsruher Institut für Technologie Encre imprimable hautement conductrice pour électronique souple hautement étirable et conducteurs ultra-étirables hautement conducteurs pouvant être obtenus à partir de celle-ci
US12180380B2 (en) 2019-03-11 2024-12-31 Karlsruher Institut für Technologie Highly conductive, printable ink for highly stretchable soft electronics and highly conductive, ultra-stretchable conductors obtainable therefrom
JP7316538B2 (ja) 2019-03-20 2023-07-28 大日本印刷株式会社 配線基板及び配線基板の製造方法
JP2020155608A (ja) * 2019-03-20 2020-09-24 大日本印刷株式会社 配線基板及び配線基板の製造方法
US11845219B2 (en) 2019-05-06 2023-12-19 Massachusetts Institute Of Technology 3-d printed devices formed with magnetic inks and methods of making graded index structures
CN111909569B (zh) * 2019-05-07 2023-09-01 施乐公司 导电油墨组合物和由其制成的制品
CN111909569A (zh) * 2019-05-07 2020-11-10 施乐公司 导电油墨组合物和由其制成的制品
CN110868815B (zh) * 2019-11-15 2021-08-13 航天恒星科技有限公司 一种曲面立体电路板制备方法及曲面立体电路板
CN110868815A (zh) * 2019-11-15 2020-03-06 航天恒星科技有限公司 一种曲面立体电路板制备方法及曲面立体电路板
CN111154253B (zh) * 2019-11-20 2021-09-07 江苏集萃先进高分子材料研究所有限公司 一种用于选择性激光烧结3d打印的压电聚氨酯粉体材料
CN111154253A (zh) * 2019-11-20 2020-05-15 江苏集萃先进高分子材料研究所有限公司 一种用于选择性激光烧结3d打印的压电聚氨酯粉体材料
CN110907501A (zh) * 2019-12-10 2020-03-24 新余学院 一种应变不敏感的柔性可拉伸温度/湿度传感器及其制备方法
WO2022180577A1 (fr) * 2021-02-24 2022-09-01 Universidade De Coimbra Circuit imprimé souple, encre et procédé d'obtention d'un circuit imprimé souple de celui-ci
CN113724921A (zh) * 2021-09-22 2021-11-30 宁波韧和科技有限公司 一种柔性结构单元、柔性压力开关与柔性压力传感器
CN113724921B (zh) * 2021-09-22 2022-06-14 宁波韧和科技有限公司 一种柔性结构单元、柔性压力开关与柔性压力传感器
IT202200014269A1 (it) * 2022-07-06 2024-01-06 Scuola Superiore Di Studi Univ E Di Perfezionamento Santanna Elettrodo neurale realizzato con polimeri soft e tecniche di rapid prototyping
WO2024009237A1 (fr) * 2022-07-06 2024-01-11 Scuola Superiore Di Studi Universitari E Di Perfezionamento Sant'anna Électrode neuronale faite de polymères souples et techniques de prototypage rapide
CN116884668A (zh) * 2023-06-30 2023-10-13 芯体素(杭州)科技发展有限公司 适用于3d打印弹性探针的导电弹性银浆及其制备方法与应用
CN116884668B (zh) * 2023-06-30 2025-05-16 芯体素(杭州)科技发展有限公司 适用于3d打印弹性探针的导电弹性银浆及其制备方法与应用

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