WO2019203871A1

WO2019203871A1 - Membrane-coating stereolithography

Info

Publication number: WO2019203871A1
Application number: PCT/US2018/045113
Authority: WO
Inventors: Chunguang Xia; Junlin Cai; Liangkang FU; Nicholas Fang; Xiaoning He
Original assignee: Bmf Material Technology Inc
Current assignee: Bmf Material Technology Inc
Priority date: 2018-04-17
Filing date: 2018-08-03
Publication date: 2019-10-24
Anticipated expiration: 2020-10-17
Also published as: CN112823313B; CN112823313A

Abstract

Membrane-coating stereolithography (MCSL), a novel 3D printing technology, is provided, which employs the transfer of working resin to the manufacture are as a coating on a membrane, and curing of the resin using, e.g., advanced micro-display technology. MCSL allows one to quickly change materials of manufacture.

Description

MEMBRANE-COATING STEREOLITHOGRAPHY

BACKGROUND

US 4,575,330 discloses a system for forming three dimensional objects by sequentially forming solid layers from photo-reactive liquid materials via UV curing, one on top of the other until a 3-D object was formed, each layer being a cross section of the objection at that particular position. This process is also commonly known as stereolithography.

Stereolithography was originally conceived as a rapid prototyping technology. Rapid

prototyping refers to a family of technologies that are used to create true-scale models of production components directly from computer aided design (CAD) in a faster manner. Since it development, stereolithography has greatly aided engineers in visualizing complex three- dimensional part geometries, in detecting errors in prototype schematics, in testing critical components, verifying theoretical designs etc., rapidly and at relatively low costs. Efforts to find improvement in this field continue. For example, work in the field of micro-electro-mechanical systems (MEMS) have led to the emergence of micro-stereolithography (mdί) which operates using the basic principles of traditional stereolithography but with much higher spatial resolution.

Assisted by single-photon polymerization and two-photon polymerization techniques, the resolution of mdί was further enhanced to be less than 200 nm. However, the serial nature of tracing a layer spot on a resin surface in mdί dramatically drags down the speed of fabrication and complicates the laser driving system, which lead to the invention of a new parallel technology, projection micro-stereolithography (RmdI ).

The core of Rmdί technology is a high resolution spatial light modulator which is either a liquid crystal display (LCD) panel or a digital light processing (DLP) panel. Although Rmdί has shown faster fabrication speeds than traditional mdί, it still takes tens of hours for Rmdί to fabricate a centimeter-scale sample with sub-10-mhi resolution. Furthermore, Rmdί provides no significant advantage in multi-material fabrication, since switching materials during Rmdί processes will dramatically reduce the speed.

Technologies based on flow lithography were developed that provides methods to quickly fabricate polymeric 2D micro particles by exposing mask images on a flow of polymer solution in a polydimethylsiloxane (PDMS) channel that allowed for the use of multiple materials of fabrication. These micro particles can be assembled into a more complicated 2D structure by introducing a guided rail in the channel. However, these technologies are basically 2D fabrication methods.

Therefore, methods were developed wherein a PDMS membrane is deformed to create multi layered micro-structures,“Three-dimensional fabrication of heterogeneous microstructures using soft membrane deformation and optofluidic maskless lithography”, Seung Ah Lee, Su Eun Chung, Wook Park, Sung Hoon Lee and Sunghoon Kwon, Lab Chip, 2009, 9, 1670-1675. Due to the limited membrane deformation, the formed structures are often less than 5 layers.

Nevertheless, a fast 3D micro-fabrication technology capable of multi-material fabrication is still needed. For example, although direct writing 3D printing methods using multiple injectors can enable the multi-material fabrication, the serial nature of the method limits its speed and resolution is around 100 microns due to nozzle fluidic limitations.

SUMMARY OF THE INVENTION

The present invention provides a new technology, membrane-coating stereolithography (MCSL), for quick 3D multi-material micro fabrication. This new technology makes use of an elastic and oxygen permeable polymer membrane, e.g., a PDMS membrane, which not only eliminates the free, open surface in traditional RmBί, thus dramatically increases the fabrication speed, but also provides a means to quickly switch materials during fabrication using advanced coating scrubbers. By taking advantage of the dedicated fluid control, an arbitrary sophisticated multi-material structure can be achieved, even with free particles encapsulated. Such a combination of advantages provides a powerful and promising tool in, e.g., emerging research areas covering material science, cell biology, and tissue engineering.

Broad embodiments include a system and a method for producing a three-dimensional object from a fluid medium, said system comprising:

a resin composition curable by exposure to radiation,

a radiation source supplying the radiation used to cure the resin,

an exposure or reaction area where the resin is cured by exposure to the radiation,

a membrane, transparent to the radiation used to cure the resin, which is positioned between the radiation source and the resin during exposure of the resin to the radiation, one or more coating scrubbers that deposit the resin on a side of the membrane away from the radiation source,

a membrane assembly comprising the exposure / reaction area, a container for holding resin or carrier especially in the exposure / reaction area, and a movable sample holder or platform on upon which the object is formed

and a control system.

At the beginning of the present 3D printing process, in many embodiments, the container is filled with a resin, such as a working resin used in the 3D printing process, or a resin compatible liquid or solution with similar or higher density than the working resin, so that the fresh coating is kept above the older resin. The resin or resin compatible liquid is added to the container to a level sufficient to remove any air below the membrane to avoid defects caused by air being present. When printing with more than one resin, different working resins will be injected from the coating scrubbers, and typically the container will be filled with the compatible liquid or solution rather than a curable resin. In another embodiment, a resin immiscible heavy liquid metal is added to the container at the beginning of the process. When using a liquid metal, a space of 100 urn to 1000 urn remains between the membrane and the liquid metal free surface. The liquid metals can be, e.g., mercury, gallium or their alloys, such as galinstan, but they must be liquid at the working temperature.

During the process, the membrane is brought into a position relative to a scrubber to enable coating with the working resin. In various embodiments, this is accomplished by moving the scrubbers, the membrane, or both. Typically, the membrane and/or scrubbers are moved so that the membrane makes contact with the scrubber.

In a second step, the membrane begins moving toward its exposure position in the reaction area between the irradiation source and container, while at the same time the scrubber releases and coats the contact side of the membrane with the fresh resin. As each scrubber may be connected to two kinds of resin, it may be necessary to flush out a previously applied resin before delivering the present resin. It is also possible to deliver two materials simultaneously in one scrubber controlling as discussed below. The thickness of the applied coating is the combined results of the resin flow rate and the relative moving speed of the membrane, which can be accomplished by moving the membrane, scrubbers, or both. When a liquid metal is used in the container, the coating thickness is defined by the space or gap between the membrane and the liquid metal free surface.

Once the membrane is coated with the working resin and positioned between the irradiation source and the sample holder, the working resin, in a third step, is subjected to digital image exposure at designed light intensity and duration. If one exposure is not large enough to cover the whole coating area, a multiple exposure scheme can be applied by translating x, y stages in steps of picture size. Spatially adjacent exposures have a minimum amount of overlap (typically 20 microns) at the shared edges to fuse the two exposures together.

The above steps of the process are repeated, adjusting the digital image exposure and resin as needed until the object is fully formed. The coating system is symmetrical; therefore, the membrane can be moved back along the same path to be recoated by the same scrubber, or it can continue forward toward a second scrubber.

In the present application,“a” or“an” means one or more than one unless stated otherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a schematic drawing of a membrane-coating stereolithography system

Figure 2 is 3D view on the details of the scrubber coating assembly

Figure 3 is coating scrubber

Figure 4, 3D view of the coating system with two scrubbers fixed to a moving stage during resin coating

Figure 5, Resin coating process in MCSL, the membrane and the resin container move.

Figure 6, Deformation of the membrane at 1 mm engagement with scrubber

Figure 7, Resin coating process in MCSL, the membrane moves only.

Figure 8, Resin coating process in MCSL, the scrubbers move only and stay on different sides of the working area.

Figure 9, Resin coating process in MCSL, the scrubbers move only and both scrubbers stay on the same side of the working area.

Figure 10, Method of coating two materials simultaneously in MCSL DESCRIPTION OF THE INVENTION

One embodiment of the invention provides a system for producing a three-dimensional object from a fluid medium, e.g., Figures 1 , 2 and 4. Another embodiment is a method for producing a three-dimensional object from a fluid medium using said system. In the present application, a fluid medium can be a particle suspension.

For example, in one embodiment a system is provided for producing a three-dimensional object from radiation curable, e.g., photo curable, resins. Such a system comprises:

a radiation source, for example, a light engine with a micro display (liquid crystal on silicon (LCOS) or DLP panel), and optics for image delivery and to monitor the system, a membrane, transparent to the radiation used to cure the resin, positioned between the

radiation source and the resin during exposure of the resin to the radiation:

one or more coating scrubbers that deposit resin on a side of the membrane away from the radiation source,

a resin delivery system and reservoirs to hold and supply the curable resin or resins;

a membrane assembly comprising an exposure / reaction area in which the resin is cured by exposure to the radiation, a mechanism for holding and positioning the membrane and/or coating scrubbers during the process, and a sample holder or platform on upon which the object is formed; and

a control system, typically a control computer with automation stages.

The irradiation or light source provides curing radiation as an image to the exposure area, which image can quickly change as the process proceeds. One means for providing such as image is LCOS, also known as reflective LCD, which is generally considered to be more effective than traditional standard LCD in terms of image brightness and contrast. Each pixel of LCOS can modulate the polarity of a reflected incident light beam under application of electro voltage. Thus, with a polarizer in the path of the reflected light beam, the amount of transmitted light is controlled by the voltage at the electros of each LCOS pixel.

DLP is an alternative display technology first developed by Texas Instruments in 1987. Instead of modulating the polarity of reflected light beam, each pixel in DLP chip is an individual micro mirror which tilts the direction of the reflected light by changing the angle of each micro mirror. The angle can be tilted up to ±10°. A bright pixel directs the light through the lens; however, a dark pixel guides light away from the lens. The grayscale of images is controlled by switching the angle of mirror between bright and dark states at different frequencies. DLP panels have advantages over LCOS panels in terms of UV compatibility and higher contrast ratio.

The light source should have a uniform illumination field with wavelengths that properly interact with the working wavelength of micro display and the light absorption profile of the resins. Much of the work described herein used a light source with a wavelength of 405nm, but other wavelengths may be used.

In many embodiments of the present invention, excellent results were obtained using a DLP panel with native resolution 1920X1080, each pixel of the DLP panel being about 7.6 mhi X 7.6 mhi in size.

Optics used in these embodiments included an OEM light engine for the micro display, a beam splitter for CCD camera monitoring, a projection lens, and other accessories. A projection lens is used to project the micro display image onto the wet surface of the transparent membrane, where photo-polymerization takes place. With a magnification of the projection lens about 6.6, the image of each pixel is 50microns X 50microns.Therefore, for one full-size exposure, it covers an area of 96mm X 54mm. The CCD camera is for monitoring the working site and helps perform the auto-focus on the membrane and the sample holder.

The membrane of the invention is used to transport resin to the exposure / reaction area where the resin is cured and becomes part of the object being produced. Obviously, the membrane must not react with the working resin, and preferably the membrane is“non-stick” so that the resin can readily disassociate from the membrane during curing. The membrane must also be transparent in the wavelengths used in curing. Any material producing a flexible membrane and meeting these requirements may be used in the production of the membrane. In one embodiment, a PDMS membrane is employed. For example, good results were obtained using a 150-micron thick PDMS membrane which was stretched about 10% during assembly for good flatness and mechanical response.

The membrane is coated with the working resin by interacting with scrubbers. The system typically has at least 2 scrubbers, and each scrubber can accommodate more than one resin, typically two resins. Thus, the system can readily accommodate up to 4 different resins, 2 for each scrubber. When using multiple working resins, the individual resins are conveniently stored in separate reservoirs from which they are delivered to the scrubbers. The temperature and pressure of the resins are controlled independently, as the viscosity of the resins can be very different. A resin with high viscosity (>200 cps), can be heated up to reduce the viscosity for delivery.

The coating scrubber of the invention is shown in Figure 3 and comprises a tube with holes for exuding the resin along the span of the tube that contacts the membrane. The holes are oriented in a way to ensure a uniform coating as the membrane is pulled over the scrubber. For example, in one embodiment, half of the holes form 65° angle to the tube plane, while the other half are perpendicular to the tube plane, and they are alternating. Figure 4 illustrates one way of aligning two scrubbers in a membrane assembly. As discussed below, the system can be designed so that the membrane and the resin containers are movable while the scrubbers are stationary; the scrubbers can move while the membrane and the resin containers are stationary; or in one embodiment, only the membrane moves during operation.

A membrane assembly of the invention houses:

an exposure / reaction area wherein the curing reaction occurs,

a holder for the membrane and, in embodiments where the membrane is moved during

operation a means for moving the membrane;

supports for the scrubbers and, in embodiments where the scrubbers are moved during

operation a means for moving the scrubbers,

a movable sample holder or platform on upon which the object is formed; and

a container for resin and/or other compatible liquid or resin immiscible liquid metal, also called a resin container, with an overflow hole.

In many embodiments the membrane assembly also comprises supports for a projection lens of the irradiation source. For example, in Figures 1 and 2, supports for a projection lens are integrated with resin inlet tubing of the scrubbers.

In many embodiments, the membrane assembly container is, at least in the reaction area, filled with a resin, such as a working resin used in the 3D printing process, or a compatible liquid or solution with similar density as the working resin. The resin or compatible liquid in the container should be added to a level sufficient to remove any air below the membrane to avoid defects caused by air being present. Generally, the entire container is filled with the resin or other liquid, however, certain container designs may have areas with higher walls to prevent an inadvertent spill. Alternately, the container is filled with a resin immiscible heavy liquid metal at a level that is from 100 mhi to 1000 mhi from the membrane. As the resins keep being injected into the resin container during the 3D printing, a drain mechanism is incorporated to prevent overflow of the container. It can be a tube with one end connected to the resin container at the height of the membrane and the other end connected to the drain. Thus, regardless of the design, the container has an overflow hole situated to prevent the level of the resin or resin and other liquid from getting too high in the area of the reaction. As stated above, when printing with more than one resin the container will typically be filled with a compatible liquid or solution or resin immiscible liquid metal rather than a curable resin at the outset of the operation.

In order to properly coat the membrane with the working resin, it will have to contact the scrubber, typically by lowering the membrane or raising the scrubber, which deforms the membrane. The deformation of the membrane has a negative impact on resolution in the working area, Figure 6 shows the pattern of deformation, thus it is necessary to disengage the membrane and the scrubbers at the time of image exposures or suppress the deformation with a straight bar pushing against the membrane. A means for vertical movement as well as horizontal movement of the scrubbers and / or membrane is typically incorporated into the present system.

As one exemplary embodiment, the system can employ:

1 ) a light source having a uniform illumination field with a wavelength of 405 nm, a DLP panel with native resolution 1920X1080, with each pixel of the DLP panel is around 7.6 mhi X 7.6 mhi in size using optics that include an opto-electro-mechanical light engine for the micro display, a beam splitter for the CCD camera monitoring, and a projection lens to project the micro display image to the wet surface of the transparent membrane. In one example, wherein the magnification of the projection lens here is about 6.6, the image of each pixel is 50 microns X 50 microns, and one full-size exposure covers an area of 96mm X 54mm, working wavelength is 405 nm;

2) a 150-micron thick PDMS non-stick membrane with an effective size of the membrane of 350mm X 80mm; 3) reservoirs for up to 4 resins with temperature controls and regulated pressure, e.g., air pressure, for delivery;

4) two coating scrubbers of the general shape shown in Figure 3, having dimensions designed to cover the size of the fabrication sample and comprising a stainless steel tube of 5mm outer diameter and 3mm inner diameter, 0.5mm diameter holes with 1 mm pitch over a span of 60mm, wherein the orientation of the holes is designed to ensure a uniform coating as the membrane is pulled over the scrubber. In this example, half of the holes form 65° angle to the tube plane, the other half are perpendicular to the tube plane and they are alternating.

In one embodiment, the above system is designed so that in the membrane coating process the membrane and the resin container move while the scrubbers are stationary, schematically shown in Figure 5. The membrane is coated uniformly with the resin as it moves across the scrubber. A coating simulation using a resin with a viscosity of around 40 cps and a diffusion coefficient 2.5x10-6 cm2/s, shows that when the membrane scrubs the coating scrubber at a speed of 1 cm/s, and the scrubber releases resin at a rate of 0.7ml/s, after 10s, it can uniformly coat the membrane over an area of 100 mm X 60 mm at a thickness of around 1 mm. These parameters can be optimized to further improve the coating performance, for this embodiment and other embodiments wherein different elements are movable in the coating process.

In another such embodiment, the above system is designed so that in the membrane coating process the scrubbers move while the membrane and the resin container are stationary as schematically illustrated in Figure 8 or 9. When designed to move the membrane and the resin container instead of the scrubbers, the system can eliminate an additional translation stage, thus reduce the cost of goods. Flowever, by reversing the moving parts, i.e., moving only the scrubber, one can reduce the size of the membrane and the resin container.

In another embodiment, the system is designed so that only the membrane moves

schematically shown in Figure 7. Simulation show that in this embodiment, due to the relative shear movement between the membrane and the resin in the container, the fresh resin coating is thicker, increasing more than 50% compared to that in the cases where only the scrubbers move, or the membrane and the container move together. One advantage of the moving the membrane only architecture is that it save the time on translating the sample down and up for coating. Generally speaking, the process of the present invention comprises situating a membrane coated on the underside with one or more radiation curable resins between a holder or reaction stage situated in a container and a radiation source, irradiating the resin with a defined pattern of light to cure the resin to make it a layer that is part of a 3-D object, and then repeating the process to form additional resin layers. The pattern of light used to cure the resin layer can be changed as needed so the desired shape is produced.

Before the process begins the container generally is filled with a resin or other compatible liquid as described above to a level that will displace any air underneath the membrane to prevent any defects caused by air being present. Alternately the container is filled with a resin immiscible liquid metal. The holder may need to be moved to the appropriate position. The object will be formed on the holder or reaction stage, and movement of the holder up or down will often occur between the iterations resin curing and deposition.

The resin is deposited onto the membrane via the scrubber. This requires the membrane and scrubber to move relative to each other. As seen in the figures, the relative motion of the membrane and scrubber is perpendicular to the line of holes on the scrubber used for dispensing of the resin. In addition, the membrane contacts the scrubber as it is coated and typically disengages from the scrubber afterwards, requiring vertical movement of the scrubber or membrane.

The process of the invention will be described using a 3D printing system from above designed so that only the membrane moves during the membrane coating process, however, it will be readily apparent to one skilled in the art how these principles apply to other embodiments, i.e., only the scrubbers move or the membrane and container move.

At the start of the process of the invention, the resin container is filled to a level high enough to remove any air below the membrane in the reaction area in order to avoid defects caused by the air. The membrane may be filled with a compatible resin, which may be photo-sensitive or not, another liquid compatible with the working resin, or a resin immiscible liquid metal. Often, when the system is used for single material printing, the container is filled with the photo-sensitive working resin. For multiple material printing, the actual working resins will be injected into the system by the coating scrubbers and the composition of the resins or resin mixtures may vary throughout the process, therefore the container is typically filled with a compatible solution with a density similar to or greater than the working resin or resins, or a resin immiscible liquid metal, instead of a working resin itself.

In step 1 , the membrane is placed into position for coating. That is the membrane working section, i.e., the part of the membrane that carries the working resin, which has a length of about 100 mm in the exemplary embodiments above, is moved to a position, so that it will cross a scrubber to reach the exposure / reaction area.

In many embodiments, each scrubber is connected to two different resins. If the scrubber tube contains residue from a previous resin not intended to be used in the present pass, the old resin flushed out of the scrubber before the new resin is deposited. In the present case, depending on the supplied upstream pressure, the flushing may take 1 to 3 seconds.

In step 2, membrane is coated with the working resin. This occurs as the membrane moves to exposure/reaction area, passing over the scrubber, while at the same time the scrubber releases and coats the wet surface (contact side) of the membrane with fresh resin.

The scrubber will deliver the working resin as the membrane crosses it as it moves toward the reaction arena. As the membrane reaches the position for coating, it will be lowered to make contact with the scrubber and the scrubber pushes on the membrane causing a deformation, in the embodiments above, about 0.5mm~1 mm. This may change depending on the size of the printing system and the materials used in the construction of the membrane etc. As the deformation of the membrane has a negative impact on resolution in the working area, it is necessary to disengage the membrane and the scrubbers at the time of image exposures or suppress the deformation with a straight bar pushing against the membrane.

The thickness of the coating is the combined results of the resin flow rate and moving speed of the membrane, which can be adjusted as desired.

In step 3, one the coated membrane is in place, the working resin is exposed to a digital image exposure at designed light intensity and duration to effect cure. If one exposure is not big enough to cover the whole coating area, a multiple exposure scheme can be applied by translating x, y stages in steps of picture size. Spatially adjacent exposures have a minimum amount of overlap (typically 20 microns) at the shared edges to fuse the two exposures together. The process is repeated until the object is formed.

As stated above, more than one resins can be used in the present process, and it is possible to deliver more than one resin to the membrane from the same scrubber. For example, when at least one scrubber is connected to sources of a first and second curable resin, which first and second curable resins are not the same, the at least one scrubber can deposit the first light curable resin onto the membrane during one coating of the membrane, and after the first resin has been cured and made part of the final object, the scrubber can deposit the second curable resin onto the membrane during a second coating of the membrane, which is then cured to be part of the final object.

In such as process, residue from one resin may remain in the scrubber when it is time to use the other resin. Thus, some embodiments include process steps wherein between deposition of the first light curable resin on the membrane and deposition of the second light curable resin on the membrane, the scrubber is flushed of any residue from the first light curable resin, and wherein between deposition of the second light curable resin and deposition of the first light curable resin, the scrubber is flushed of any residue from the second light curable resin.

The coating system is symmetric, generally having a first scrubber on one side of the exposure area and a second scrubber on the opposite side. Therefore, the membrane can move either back to the position established during stage 1 above and get recoated by the first scrubber as before; or it can continue on to a position on the opposite side of the exposure area, whereby it will be coated by the second scrubber as it returns to the exposure area.

The specifics of the process above relate to a system wherein only the membrane moves during the coating process as schematically shown in Figure 7. Figure 5 schematically shows a version of the coating process using a system wherein the membrane and the resin container move, and the scrubbers do not. Figure 8 schematically shows the coating process where only the scrubbers move and stay on opposite sides of the working area, i.e., the exposure / reaction area. Figure 9, schematically illustrates the coating process wherein only the scrubbers move and both scrubbers stay on the same side of the working area. When using the process of Figure 9, coating materials alternatingly from two scrubbers reduces fabrication time compared to the method shown in Figure 8, as the scrubbers need not to move to the coating positions to start coating.

It is also possible to deliver two materials simultaneously in one scrubber, illustrated in Figure 10. For example, in one embodiment at least one scrubber is connected to sources of a first and second light curable resin, which first and second light curable resins are not the same, and wherein the at least one scrubber deposits both the first light curable resin and the second light curable resin onto the membrane during a single coating of the membrane. By controlling the pressure of each individual resin, even a bias coating can be achieved with two resins covering different areas of different sizes. This method will give MCSL flexibility to simultaneously print two parts with different material spatial architectures.

The present invention provides a novel 3D printing technology, membrane-coating

stereolithography (MCSL). It further extends the existing 3D printing principles and technologies, which are based on the advanced micro-display technology, by introducing the 3D membrane coating technique. MCSL allows quick changing printing materials in and off the 3D printing plane and has great potential in fields ranging from bioengineering to inhomogeneous engineered materials.

Claims

What is claimed is:

1. A system for producing a three-dimensional object from on or more radiation curable resins, said system comprising:

a) a radiation source to supply radiation for curing a radiation curable resin,

b) a membrane for transporting radiation curable resin to a reaction area where the radiation curable resin is exposed to radiation from the radiation source, wherein the membrane is transparent to the radiation used to cure the radiation curable resin and is positioned between the radiation source and the radiation curable resin during exposure of the radiation curable resin to the radiation,

c) one or more coating scrubbers that deposit radiation curable resin on a side of the membrane away from the radiation source,

d) a resin delivery system and one or more reservoirs to hold and supply one or more radiation curable resins to the scrubbers;

e) a membrane assembly comprising a reaction area in which the radiation curable resin is cured by exposure to radiation form the radiation source, a container, a sample holder or platform on upon which the object is formed a mechanism for holding and positioning one or more of the membrane, container, and coating scrubbers; and

f) a control system.

2. The system according to claim 1 wherein the irradiation source a) comprises a light engine with micro display and optics for image delivery and to monitor the system, and the control system f) is a control computer with automation stages.

3. The system according to claim 2 wherein the micro display comprises a liquid crystal display panel or a digital light processing panel.

4. The system according to claim 3 wherein the micro display comprises a digital light processing panel.

5. The system according to claim 1 wherein the membrane is a polydimethylsiloxane

membrane.

6. The system according to claim 2, further comprising a light-curable resin.

7. The system according to claim 6 comprising at least two light curable resins.

8. The system according to claim 7 comprising at least from 2 to 4 light curable resins, 2 to 4 reservoirs, each for holding a different light curable resin, and wherein at least one scrubber is connected to the reservoirs of two different light curable resins.

9. The system according to claim 1 designed so that the membrane and the container move during deposition of resin from the scrubbers onto the membrane.

10. The system according to claim 1 designed so that the scrubbers move during deposition of resin from the scrubbers onto the membrane.

1 1 . The system according to claim 1 designed so that only the membrane moves during deposition of resin from the scrubbers onto the membrane.

12. A process for producing a three-dimensional object by curing a radiation curable resin, said process comprising:

providing a membrane, radiation curable resin, radiation source, and a container, which is

positioned below the membrane during curing of the radiation curable resin;

coating the membrane on one side with the radiation curable resin to form a coated membrane; situating the coated membrane between a sample holder located in a container and the

radiation source, wherein the side of the coated membrane that was coated is facing away from the radiation source,

wherein the container is filled with a resin or a resin compatible liquid with a similar or higher density than the radiation curable resin to a level that will displace any air underneath the membrane, or the container is filled with a resin immiscible heavy liquid metal to a level wherein a space of 100 urn to 1000 urn remains between the membrane and surface of the liquid metal;

irradiating the radiation curable resin with a defined pattern of radiation to cure the resin

producing a layer that is part of a 3-D object;

repeating the process to form additional resin layers.

13. The process according to claim 12 wherein coating the membrane comprises depositing the radiation curable resin onto the membrane through one or more coating scrubbers, the radiation source comprises a light engine with micro display and optics for image delivery and to monitor the system and the radiation curable resin is a light curable resin.

14. The process according to claim 13 wherein the micro display comprises a liquid crystal display panel or a digital light processing panel.

15. The process according to claim 13 wherein the coating of the membrane, situating the membrane between the radiation source and the holder, and irradiation of the resin are controlled by a control computer with automation stages.

16. The process cording to claim 13 wherein the membrane is a polydimethylsiloxane membrane.

17. The process according to claim 15 wherein the membrane, one or more coating scrubbers, and container are comprised by a membrane assembly, said assembly comprising means for moving the membrane, coating scrubbers, and container, individually and in combination.

18. The process according to claim 17 wherein the membrane assembly comprises at least two coating scrubbers.

19. The process according to claim 18 wherein the membrane and the container move while the scrubbers do not move during deposition of the radiation curable resin from the scrubbers onto the membrane.

20. The process according to claim 18 wherein the scrubbers move while the membrane and container do not move during deposition of the radiation curable resin from the scrubbers onto the membrane.

21 . The process according to claim 18 wherein the membrane moves while the scrubbers and container do not move during deposition of the radiation curable resin from the scrubbers onto the membrane.

22. The method according to claim 17 wherein at least two light curable resins are used during preparation of the resin layers.

23. The method according to claim 22 wherein at least one scrubber is connected to sources of a first and second light curable resin, which first and second light curable resins are not the same, and wherein the at least one scrubber deposits the first light curable resin onto the membrane during one coating of the membrane and deposits the second light curable resin onto the membrane during a second coating of the membrane.

24. The method according to claim 22 wherein at least one scrubber is connected to sources of a first and second light curable resin, which first and second light curable resins are not the same, and wherein the at least one scrubber deposits both the first light curable resin and the second light curable resin onto the membrane during a single coating of the membrane.