WO2008068680A2

WO2008068680A2 - Fluidic cell manipulator

Info

Publication number: WO2008068680A2
Application number: PCT/IB2007/054841
Authority: WO
Inventors: Dirkjan B. Van Dam; Thomas J. De Hoog; Judith M. Rensen; Simone I. E. Vulto
Original assignee: Koninklijke Philips Electronics NV
Current assignee: Koninklijke Philips NV
Priority date: 2006-12-01
Filing date: 2007-11-29
Publication date: 2008-06-12
Anticipated expiration: 2009-06-01
Also published as: CN101548172A; WO2008068680A3; BRPI0719508A2; JP2010510803A

Abstract

A system (100) is described for individually manipulating, e.g. orienting, a particle (104) in a fluid (106). The manipulating system (100) comprises a particle trapping system (111) allowing trapping of the particle (111) in a fluid channel (102) and a controller for controlling shear force gradients on the particle. Shear force gradients on the particle are 5 controlled by positioning a particle off center in the fluid channel (102) in a laminar flow or by controlling the laminar flow itself. The laminar flow thereby is generated using a flow generator (108). The system (100) for manipulating may be used in a particle characterization system or may be used for performing actions on the particle (104) under predetermined orientations.

Description

FLUIDIC CELL MANIPULATOR

FIELD OF THE INVENTION

The present invention relates to the field of particle characterization and manipulation. More particular, the present invention relates to methods and systems for manipulating objects or particles, such as e.g. biological cells, in view of their inspection or characterization as well as to software for carrying out such methods.

BACKGROUND OF THE INVENTION

Characterization of analytes is often used in chemical, biochemical or biological tests in order to detect presence of certain types of analytes. For example, by detecting and/or characterizing cell properties, it is in principle possible to detect malignant cells such as e.g. precancerous cells, opening the possibility to detect and/or monitor the progress of diseases, e.g. from preinvasive to invasive. Detection and/or characterization of single particles, as often used in biosensor applications, thereby allows obtaining qualitative and quantitative results. One option for detecting single particle characteristics is to selectively bind particles of interest to a surface and sense their particular characteristics.

Another option for detecting single particle characteristics is by trapping single particles in a fluid using trapping systems.

A number of different trapping techniques is known, such as using optical trapping systems for example based on lasers, also known as tweezers, using dielectrophoresis, using an acoustic field, using contraction of a flow channel, etc. Most of these techniques do not allow determination or control of the orientation of the cell. The orientation of the cell nevertheless may play a significant role in the characterization of the cell, as for example erroneous detection might occur when the particle hinders detection of a particle feature present at the back side of the particle or when a predetermined orientation of a particle is advantageous for performing a handling on that particle. In other words, the impact of being able to orient a particle to be characterized or treated on research and single- cell applications may be significant.

In International patent application WO 2006/059109 a single cell analyzer is described wherein trapping and manipulation of cells is performed using an optical trap. The optical trap uses a laser and focusing lens for manipulating the cell within the optical trap. By moving the focused laser beam in three dimensions, the position of the cell can be changed, by adjusting a separation between multiple spots the cell can be stretched or compressed and by rotating the polarization of the beam or the pattern of beam spots, the cell can be rotated.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide good systems and methods for manipulating particles in a fluid as well as to software for carrying out such methods. It is an advantage of embodiments of the present invention that systems and methods are obtained wherein the orientation of particles, e.g. single particles, can be selected for characterization, detection and/or treatment purposes. The above objective is accomplished by a method and device according to the present invention.

The present invention relates to a system for individually manipulating a particle in a fluid, the system comprising a flow generator adapted for generating a laminar fluid flow of the fluid in a fluid channel, and a particle manipulator adapted for trapping and orienting the particle in the fluid channel by controlling a net shear force induced by the laminar fluid flow on the particle. The particle manipulator may be adapted for controlling the orientation and/or rotation of the particle by changing a position of the particle in a flow field of the laminar flow of the fluid and/or by changing a velocity distribution in a flow field of the laminar flow of the fluid. Providing a net shear force may be performed by introducing the particle in a shear force field having a shear force gradient. The particle thereby may be rotated by a shear force at one side being larger than a shear force on the other side, resulting in a net shear force on the particle. It is an advantage of embodiments of the present invention that the system allows altering the orientation of a particle. It is furthermore an advantage of embodiments of the present invention that accurate orienting and positioning of a particle can be obtained. It is also an advantage of embodiments of the present invention that a single particle manipulating system may be obtained. It is also an advantage of embodiments of the present invention that each required orientation of the particle can be obtained. The particle manipulator may act directly on the particle to be trapped or may act on a such a particle by acting on a label bound to the particle.

The particle manipulator may comprise a particle position controller for controlling a position of the particle in a direction substantially perpendicular to a flow direction of the laminar fluid flow. It is an advantage of such embodiments that the trapping system and particle position controller can be the same component, i.e. that the positioning and trapping action can be performed by the same component. It is also an advantage of such embodiments that the orientation can be controlled by the position of the particle, allowing to operate the system in continuous flow.

The particle position controller may be adapted for moving the particle to a predetermined position in the fluid channel where a predetermined net shear force on the particle is induced by the laminar flow. It is also an advantage of such embodiments that the particle position controller allows accurately moving the particle. It is an advantage of such embodiments that the rotating direction of the particle can be selected. It is also an advantage of such embodiments that the amount of rotation required can be easily set and can be accurately obtained. It is an advantage of such embodiments that the required orientation can be efficiently obtained.

The shape of the fluid channel may be adapted such that the fluid channel comprises at least one position in a trapping region for the particle wherein no net shear force acts on the particle when a laminar flow is present. It is an advantage of such embodiments that the system can be used with continuous laminar flow regime. The particle position controller may be adapted for moving the particle to the position wherein no shear force gradient acts on the particle when a laminar flow is present.

The particle manipulator adapted for controlling a net shear force induced by the laminar fluid flow on the particle may be adapted for controlling an intensity of the laminar fluid flow generated by the flow generator.

The particle manipulator may comprise a flow controller for controlling an intensity of the laminar fluid flow generated by the flow generator. The flow intensity, e.g. determined by the maximum flow velocity, may be such that the maximum flow velocity varies between 0 and a predetermined maximum flow velocity. Controlling the net shear force may comprise controlling the ON/OFF state of the flow generator and/or the flow velocity of the laminar fluid flow. It is an advantage of such embodiments that the system can be used for various types of fluid channels, e.g. for various shapes of fluid channels. It is also an advantage of such embodiments that the rotation speed of the particles can be selected.

The particle manipulator may comprise at least one optical tweezer. The particle manipulator may comprise two crossed optical tweezers. The optical tweezers may comprise settable and adjustable focus points allowing to position particles in two non- parallel directions perpendicular to the flow direction.

The particle manipulator may comprise at least one dielectrophoretic trap. The system further may comprise a feedback system for determining a position and orientation of a particle and for providing feedback control signals to the particle manipulator. It is an advantage of the system according to such embodiments that manipulating can be performed in an automated and/or automatic way. The system further may comprise a handling system adapted for injecting material in and/or extracting material out of the particle under a predetermined orientation of the particle. It is an advantage of such embodiments that more accurate handling of particles may be obtained, without the need for biochemically orienting particles.

The flow generator may be adapted for providing a maximum flow velocity of the laminar fluid flow between 0 m/s and 10^~3 m/s. Alternatively or in addition thereto, the flow controller may be adapted for providing a maximum flow velocity of the laminar fluid flow between 0 m/s and 10^~3 m/s. The maximum flow velocity, which may be the velocity at the center of the fluid channel, may be at least between 0 mm/s and 10^~3 m/s. Alternatively or in addition thereto the maximum flow velocity may be at least 10^~5 mm/s, e.g. at least 10^~4 mm/s, e.g. at least 10^~3 mm/s.

The system may be adapted for individually manipulating biological cells. The present invention also relates to a characterization system for charactering a particle, the particle characterization system comprising a system for individually manipulating a particle in a fluid as described above, e.g. a system comprising a flow generator adapted for generating a laminar fluid flow of the fluid in a fluid channel, and a particle manipulator adapted for trapping and orienting the particle in the fluid channel by controlling a net shear force induced by the laminar fluid flow on the particle, and the characterization system furthermore adapted for determining a characteristic property of the particle. The characterization system may comprise a detection means for detecting a magnetic or optical property of the particle or of a label bound to the particle. It is an advantage of embodiments according to the present invention that a more accurate and/or efficient characterization of particles may be performed.

The present invention furthermore relates to a method for individually manipulating a particle in a fluid, the method comprising generating a laminar fluid flow of the fluid in a fluid channel, individually trapping the particle in the fluid channel, and orienting the particle by controlling a net shear force induced by the laminar fluid flow on the particle. Controlling a net shear force may be performed by introducing the particle in a shear force field having a shear force gradient. Orienting the particle may comprise controlling the orientation and/or rotation of the particle by changing a position of the particle in a flow field of the laminar flow of the fluid and/or by changing a velocity distribution in a flow field of the laminar flow of the fluid. The particle thereby may be rotated by a shear force at one side being larger than a shear force on the other side, resulting in a net shear force on the particle. The controlling may comprise bringing the particle in a laminar flow field creating a shear force gradient on the particle. The controlling may comprise inducing a shear force gradient on the particle by switching the laminar flow field ON. Manipulating the particle may be orienting the particle. Manipulating the particle may be manipulating a biological cell.

The present invention also relates to a method for characterizing a particle in a fluid comprising individually manipulating the particle according to the method for manipulating a particle in a fluid as described above such that a predetermined orientation of the particle is obtained, and determining a property of the particle under the predetermined orientation.

The present invention also relates to a controller for use in a system for individually manipulating a particle, e.g. a biological cell, in a fluid as described above.

The present invention also relates to a computer program product for, when executed on a computing means, performing a method for individually manipulating a particle, e.g. a biological cell in a fluid, the method comprising generating a laminar fluid flow of the fluid in a fluid channel, individually trapping the particle in the fluid channel, and orienting the particle by controlling a net shear force induced by the laminar fluid flow on the particle.

The present invention furthermore relates to a machine readable data storage device storing the computer program product as describe above and/or the transmission of such a computer program product over a local or wide area telecommunications network. It is also an advantage of embodiments of the present invention that efficient systems and methods are obtained for orienting objects or particles, e.g. single particles. It is an advantage of embodiments of the present invention that no complex trapping systems, such as e.g. laser systems with multiple spots or with rotatable laser beams, are required. It is furthermore an advantage of embodiments of the present invention that orienting of particles may be performed in an accurate way. It is also an advantage of embodiments of the present invention that orienting of particles may be performed in a controlled way. It is an advantage of embodiments of the present invention that initial orientation, e.g. being random orientation, of trapped particles, e.g. cells, can be altered and can be controlled. In other words, particular embodiments of the present invention provide control mechanisms that allow rotating particles in a controlled way. It is also an advantage of embodiments of the present invention that the particles oriented using such methods and systems are minimally disturbed, changed and/or damaged, e.g. because there is no mechanical contact required.

Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.

The teachings of the present invention permit the design of improved methods and apparatus for characterization and/or treatment of particles, e.g. for optical characterization of particles. The above and other characteristics, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. This description is given for the sake of example only, without limiting the scope of the invention. The reference figures quoted below refer to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a schematic representation of a system for manipulating particles according to an embodiment of the first aspect of the present invention. Fig. 2 is a schematic representation of the influence of a fluid flow on a particle in the fluid flow, as may occur in a system for manipulating particles according to an embodiment of the first aspect of the present invention.

Fig. 3 is a graph of the velocity versus position in the cross section of an axial symmetric fluid channel, as may be exploited in a system for manipulating particles according to an embodiment of the first aspect of the present invention.

Fig. 4 is a graph of the shear force versus position in the cross section of an axial symmetric fluid channel, as may be exploited in a system for manipulating particles according to an embodiment of the first aspect of the present invention.

Fig. 5 and Fig. 6 is a schematic representation of (part of) an exemplary system for manipulating particles using two optical tweezers as vertical and horizontal positioning means of particles according to a first particular embodiment of the first aspect of the present invention. Fig. 7 is a schematic representation of the positioning of a cell by light beams as can be used in a system for manipulating particles according to an embodiment of the first aspect of the present invention.

Fig. 8 is a schematic representation of a system for manipulating particles using one optical tweezer as positioning means of particles, according to a second particular embodiment of the first aspect of the present invention.

Fig. 9 is a schematic representation of a characterization system for characterizing particles according to an embodiment of the second aspect of the present invention. Fig. 10 is a schematic representation of a computing system as can be used for performing a method of manipulating particles according to an embodiment of the fourth aspect of the present invention.

In the different Figures, the same reference signs refer to the same or analogous elements.

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. Any reference signs in the claims shall not be construed as limiting the scope. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes.

Where the term "comprising" is used in the present description and claims, it does not exclude other elements or steps. Where an indefinite or definite article is used when referring to a singular noun e.g. "a" or "an", "the", this includes a plural of that noun unless something else is specifically stated. Furthermore, the terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. Moreover, the terms top, bottom and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequence and/or orientations than described or illustrated herein. Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may do so. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

Furthermore, some of the embodiments are described herein as a method or combination of elements of a method that can be implemented by a processor of a computer system or by other means of carrying out the function. Thus, a processor with the necessary instructions for carrying out such a method or element of a method forms a means for carrying out the method or element of a method. Furthermore, an element described herein of an apparatus embodiment is an example of a means for carrying out the function performed by the element for the purpose of carrying out the invention.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. The following terms or definitions are provided solely to aid in the understanding of the invention.

Where in the present invention the term "particle" is used, reference may be made to chemical, biochemical or biological particles, e.g. that need to be detected, such as for example but not limited to cells, cellular organelles, membranes, bacteria, viruses, chromosomes, DNA, RNA, small organic molecules, metabolites, proteins including enzymes, peptides, nucleic acid segments, spores, micro-organisms and fragments or products thereof, polymers, metal ions, toxins, illicit drugs, explosives, etc. The particles preferably have a diameter larger than 0.1 μm, more preferably larger than 0.5μm, e.g. larger than lμm, as such particles typically will suffer less from additional inherent diffusive motion. Particles, especially smaller particles such as e.g. some DNA, RNA, nucleic acid segments etc., also may be coupled to larger particles in order to orient or position them. The particles may be biological cells.

Where in the present invention the term "laminar flow" is used, reference is made to a flow regime whereby the flow occurs in layers, e.g. parallel or concentric layers, depending on the shape of the flow channel. The flow may also be referred to as non- turbulent flow or streamline flow. The flow may e.g. be determined by its Reynolds Number, expressing the ratio of the product of the density, fluid velocity and average channel diameter to the viscosity. In the present embodiments, the flow may have a Reynolds number between 0 and 10, e.g. a Reynolds number between 0 and 1, e.g. a Reynolds number between 0 and 0.5.

In a first aspect, the present invention relates to a system for manipulating a particle in a fluid. The system thereby allows orientation of the particle in the fluid, which is advantageous e.g. if a particle feature is to be detected but is hidden at the backside of the particle with respect to a detection system or if a predetermined orientation for detection or handling is preferred. The system may be adapted to manipulate a single particle, i.e. to individually manipulate a particle, e.g. biological particle. The system comprises a flow generator for generating a laminar fluid flow of the fluid comprising the particle in a fluid channel and a particle manipulator for trapping the particle in the fluid channel and for controlling a shear force induced by the laminar fluid flow on the particle. The particle manipulator therefore may comprise a particle trapping system, such as e.g. an optical trapping system, using an acoustic field, using dielectrophoresis, using a deformation of the channel, and for some particles, using an electric and/or magnetic field. It furthermore may comprise a particle position controller and/or a flow controller for controlling the flow generator.

Different standard and optional components are shown by way of example in Fig. 1, the invention not being limited thereto. The different components of an exemplary system 100 for manipulating a particle 104 will further be discussed in more detail, with reference to Fig. 1 to Fig. 8.

The system 100 for manipulating the particle 104 in the fluid 106 comprises a flow generator 108. Such a flow generator 108 may for example be a (partial or full) active flow generator, comprising for example a pumping means for pumping fluid 106 through the fluid channel 102 whereby control is performed by controlling the pumping means and/or the flow generator 108 may be a (partial or full) passive flow generator, wherein the flow is generated by natural forces such as gravitational pressure or capillary forces and whereby control of the flow is performed using a valve or set of valves. The flow generator 108 is adapted for generating a laminar flow in a fluid channel 102, wherein the manipulation of the particle 104 in the fluid 106 will be performed. The flow generator 108 may for example be adapted for generating a fluid velocity such that for a given fluid viscosity and density and given fluid channel dimensions a laminar flow is obtained. When laminar flow occurs for a fluid, different shear stress is present at different positions in the flow channel. Such a flow may for example be characterized by a Reynolds number between 0 and 4000, preferably a Reynolds number between 0 and 3000, even more preferably a Reynolds number between 0 and 2000. The flow generator 108 may for example be adapted for providing a fluid velocity between 0 m/s and 10^"3 m/s, e.g. between 0 m/s and 10^"4 m/s, e.g. between 0 m/s and 1.10^"5 m/s, e.g. between 0 m/s and 1.10⁶ m/s. The dimensions and shape of the fluid channel 102 in the system 100 also may be adapted to be in a suitable range for easily obtaining laminar flow conditions. The fluid channel 102 may be of a tubular shape, e.g. an axial symmetric shape, thus generating a concentric laminar flow, i.e. a flow whereby the fluid velocity has a radial profile and where at the center of the fluid channel 102 there is substantially no net shear force on a particle 104 in the fluid flow. The fluid channel 102 also may be of substantial rectangular shape, i.e. fluid flow may for example be a fluid flow between two plates. For the ease of understanding, the embodiments and examples will be described for tubular fluid channels with an axial symmetric shape, although the invention is not limited thereto. For example, other shapes of the fluid channel 102 also may be used, having their own specific laminar fluid flow velocity profile. Although it is preferred that there is at least one point in the cross-section of the fluid channel 102 wherein the flow velocity at both sides is substantially the same such that there is no substantial net shear force on the particle 104, the invention is not limited thereto. As will be illustrated later, it then is for example also possible to control rotation by controlling the fluid flow as such.

By creating a laminar flow, in general different fluid velocities will occur at different positions in the fluid channel 102. The latter is illustrated in Fig. 2 to Fig. 4 for the example of an axial symmetric fluid channel 102, the invention not being limited thereto. In Fig. 2 it is shown that a rotation will be induced on a particle 104 if a fluid flow is present and the particle is not at the center of the fluid channel 102. The rotation will occur in the direction indicated by the arrow r. The rotation speed of the particle may depend on the flow velocity and on the position of the cell in the channel. This rotation is induced by a difference in flow velocity at two different sides of the particle 104 in the fluid 106. The velocity profile along a diameter of the axial symmetric fluid channel 102 is shown in Fig. 3, indicating the difference in flow velocity. Such a velocity profile induces a shear stress on the particle as indicated in Fig. 4. A shear stress gradient is induced by a laminar flow at all positions in the tube, except on positions on the central axis of the tube, or for more general shapes of the fluid channel in the center of the fluid channel. It can be seen in the graph of Fig. 4 showing the shear stress as function of the position, that at a center position in the fluid channel 102 the shear stress is zero resulting in no rotation, whereas closer to the walls of the fluid channel 102 the shear stress is larger, resulting in rotation. In other words, if a laminar flow is generated, a particle not present at the center or central axis of the fluid channel will start rotating in one direction. Depending on the position of the particle, negative or positive shear stress may be induced, allowing rotation of the particle 104 in different directions.

As described above, the system 100 also comprises a particle manipulator 110. The particle manipulator 110 is adapted for trapping a particle in the fluid channel 102. The particle manipulator 110 therefore preferably comprises a particle trapping system 111. The particle trapping system 111 may be adapted for trapping the particle 104 of interest in a cross-section substantially perpendicular to the fluid flow direction. The particle trapping system 111 may be based on any suitable trapping mechanism, such as for example but not limited to, an optical trapping mechanism e.g. using optical tweezers, a mechanism using dielectrophoresis, a mechanism using an acoustic field, a mechanism generating a deformation of the fluid channel 102 such as for example a system generating a contraction of the fluid channel 102, a mechanism using electric and/or magnetic forces in case magnetic or electric field sensitive particles are used, etc. If the particles to be manipulated are not sensitive to the forces used in the trapping mechanism, they may for example also be bound to an appropriate label sensitive to the forces used in the trapping mechanism. For example, when a magnetic trapping mechanism is used, a particle to be trapped may be a non-magnetic particle, bounded to a magnetic or magnetisable label. The particle trapping system 111 preferably is adapted to trap the particle 104 with sufficient force to be able to prevent the particle 104 to be dragged further in the fluid channel 102 by the fluid flow applied. By way of illustration, an example of a trapping system allowing to prevent a particle to be dragged away under the force induced by the flow velocity is shown. Optical tweezers may for example exert forces that are in the pico Newton range. In steady state, the force exerted by the flowing fluid on a spherical cell is given by 3πr\VD, where V is the fluid flow velocity, η is the fluid viscosity, and D is the cell diameter. Using η=l ^• 10^"3 Pa-s, D=I-IO^"5 m, and setting the resistive force to 1-10^"12 N, it can be seen that a flow velocity of 1 ^• 10 ⁵ m/s can be easily compensated for.

The particle manipulator 110 furthermore is adapted for controlling a net shear force induced by the laminar fluid flow on the particle 104 in the fluid channel 102. The particle manipulator 110 therefore may comprise a particle position controller 112 for controlling a position or offset of the particle in a direction substantially perpendicular to a flow direction of the laminar fluid flow. It may be adapted for moving the particle, trapped in the fluid channel 102, in a direction having at least a component perpendicular to the flow direction, i.e. to offset the particle from a particular position. The particle position controller 112 thereby may shift a particle 104 to and from a point wherein a net shear force is present induced by the laminar flow. In this way rotation of the particle 104 can be controlled by shifting the particle 104 from a point wherein no net shear force is present to a point wherein a net shear force is present, and after sufficient rotation is obtained, shifting it back to a point where no net shear force is present. For example for axial symmetric fluid channels 102, movement away and towards a center point or central axis of the fluid channel 102 may be obtained, allowing to bring the particle 104 in and out of a net shear force field induced by a laminar fluid flow. In other words, the particle position controller 112 may be used to bring the particle in and out of a gradient flow field. In a preferred embodiment the particle trapping system and the particle position controller 112 may be the same component, thus resulting in a system for manipulating at least a particle requiring less components.

Alternatively, a separate particle position controller 112 may be provided. The particle position controller 112 may be based on optical forces, e.g. by using optical tweezers, dielectrophoresis, acoustic field forces, mechanical forces e.g. by using deformation of the fluid channel 102, electric and/or magnetic forces if electric or magnetic particles are considered, etc.

Alternatively or in addition thereto, e.g. where no point in the fluid channel 102 is substantially free of a net shear force but not limited thereto, control of the net shear force induced may be obtained by controlling the laminar flow generated by the flow generator 108. In other words, alternatively or in addition to the particle position controller 112, the particle manipulator 110 may comprise a flow controller 113 for controlling activation or de-activation of the flow generator 108. Controlling activation furthermore may comprise controlling a fluid flow velocity generated in the fluid channel 102. In other words, the flow controller 113 may be used for turning ON or OFF the flow field and optionally also for varying the flow field in intensity when it is turned on. The latter allows variation of the rotation speed obtained with the system. The flow controller 113 may be in direct connection to the flow generator 108 or may be connected to the flow generator via a system controller. The flow controller and/or the flow generator may be adapted for controlling a flow such that the maximum flow velocity in the channel is between 0 m/s and 10^"3 m/s. Alternatively or in addition thereto, the flow controller may be adapted for providing a maximum flow velocity of the laminar fluid flow between 0 m/s and 10^"3 m/s, e.g. between 0 m/s and 10^"4 m/s, e.g. between 0 m/s and 1.10 ⁵ m/s, e.g. between 0 m/s and 1.10^"6 m/s. The maximum flow velocity, which may be the velocity at the center of the fluid channel, may be between 0 m/s and 10^" m/s. Alternatively or in addition thereto the maximum flow velocity may be at least 10^"5 mm/s, e.g. at least 10^"4 mm/s, e.g. at least 10^"3 mm/s.

The particle manipulator 112 thus may control the shear force on the particle by changing the position of the particle 104 in a net shear force field or by turning ON or OFF the net shear force field, e.g. by turning ON or OFF the laminar flow. The system 100 for manipulating the particle 104 in the fluid 106 also may comprise a system controller 116 for controlling the particle manipulator 110 and the flow generator 108. The system controller 116 may comprise a synchronizer 118 for synchronizing the action of the particle manipulator 110 and the flow generator 108, i.e. for example the action between the particle trapping system 111, the flow generator 108 and any of the particle position controller 112 or flow controller 113. these components thus may be adapted with an input means for receiving synchronization signals. The synchronizing may optionally be based on the input of a feedback system 114. The system controller 116 may further comprise a processor 120 for performing the different actions. The system controller 116 may operate based on predetermined algorithms, using look up tables, based on neural networks or in any other suitable way. The system for manipulating may operate in an automated and/or automatic way.

In a preferred embodiment, the system 100 for manipulating the particle 104 may comprise a feedback system 114. Such a feedback system 114 may assist in further stabilization of the system 100. One way of providing such a feedback system 114 is by incorporating a position and/or orientation detector 115 for determining the position and/or the orientation of the particle 104. The obtained positional and/or orientation information from the position and/or orientation detector may be outputted by the feedback system 114 to a controller 116 or directly to the particle manipulator 110, allowing e.g. positioning of the particle 104 at the desired position and/or rotating the particle 104 over a desired angle. The position and/or orientation detector may be an optical detection system, e.g. based on an optical detector. Optical detection of the position and orientation may be assisted by providing a unique label to the particle 104, e.g. the particle surface, and by detecting the position of the unique label on the particle 104. Such labels may be excited and corresponding excitation means also may be provided, such as e.g. an excitation irradiation source for excitation e.g. fluorescent labels, an electric and/or magnetic field generator for exciting electric and/or magnetic labels. Alternatively, the unique labels also may be inherently present in a shape or structure of the particle. The time scale of rotation of the particle thereby is suitable for obtaining relevant feedback from the feedback mechanism. For the example of the maximum fluid velocity determined above, a particle with a diameter in the range of 0.1 micrometer would have a time scale for rotation of the order of 1 second.

By way of illustration, the invention not being limited thereto, particular embodiments of the first aspect of the present invention will be discussed in more detail.

In a first particular embodiment, the present invention relates to a system 200 for manipulating a particle 104 in a fluid 106 as described above, wherein trapping of the particle 104 and controlling a net shear force on the particle 104 is performed by the same component. For example in the case controlling a net shear force on the particle 104 is performed by controlling a position of the particle 104, position control may be performed using the same mechanism as for the trapping system. In the present embodiment, the trapping system 111 therefore may be adapted for moving the particle in a direction having at least one component in a direction perpendicular to the fluid flow. It may be adapted for moving the particle substantially in a cross-section perpendicular to the fluid flow, wherein the particle is trapped. In a preferred embodiment, positioning of the particle may be performed in two non-parallel directions perpendicular to the fluid flow. One example of a system component allowing both trapping and positioning of the sample may e.g. be a set of crossed optical tweezers 202, 204, as indicated by way of example in Fig. 5 and Fig. 6. Such crossed optical tweezers 202, 204 allow both the trapping of the particle and the movement of the particle within a cross-section of the fluid channel 102. The cross-section thereby may be a cross section perpendicular to the flow direction of the fluid 106. It is an advantage of the present embodiment that the number of components required for performing the trapping and positioning of the particle is limited.

By way of illustration, the present invention and embodiment not limited thereto, a system 200 is illustrated with a tubular fluid channel 102 in Fig. 5 and Fig. 6. The optical tweezers 202, 204 performing both the trapping and movement may allow to trap the particle 104 substantially in a plane perpendicular to the flow direction. The orientation of a particle 104 may be altered by positioning the particle in a fluid flow inducing a net shear force on the particle 104. The particle therefore may be re-positioned away from the center of the fluid channel 102. Such a re-positioning is not necessary if the particle 104 is already out of the center of the fluid channel 102. The fluid flow may be continuous or may be synchronized with the re-positioning of the particle 104, e.g. by starting the fluid flow after the particle 104 has been moved outside the center, and stopping the fluid after an appropriate orientation is obtained. Depending on the fluid velocity and/or the position of the particle 104 in a cross-section of the fluid channel 102 or a combination thereof, the particle 104 will rotate more, less or not. The rotation thereby is caused by an asymmetric stress exerted on the particle 104. The speed by which the orientation changes can be altered by altering the fluid velocity. When an appropriate orientation is obtained, rotation can be stopped by positioning or re-positioning the particle 104 in the center of the fluid channel 102. As described above alternatively the fluid flow could be turned OFF, thus the fluid velocity could be brought to 0 m/s. It is to be noted that for obtaining the appropriate orientation, inertia of the particle 104 with respect to the rotational movement may be taken into account.

Alteration of the position of the trapped particle 104 in the x and/or y direction can be obtained by changing the focus point of the optical tweezers 202, 204, e.g. lasers, used. The latter may e.g. be done using controllable and adjustable lenses, such as e.g. fluid lenses, e.g. based on the electro -wetting principle or by mechanically changing the focus point, e.g. by shifting the lens. Alteration of the fluid flow may be performed using the flow generator 108. It is an advantage that by positioning the cell in an appropriate position in the fluid channel, rotation towards any desired orientation can be obtained. By using two crossed optical tweezers 202, 204, mechanical parts for covering movement of a particle in one direction can be avoided. It is an advantage of such embodiments that symmetric forces are obtained in x- and y-direction. By way of illustration, the positioning of a particle 104 in a cross-section of the fluid channel 102 is illustrated using two irradiation beams 206, 208 in Fig. 7. In a second particular embodiment, the present invention relates to a system

250 as described above, e.g. in the first particular embodiment, but wherein the particle manipulator 110 is based on a single optical tweezer 252 that can be mechanically moved. In other words, only a single optical irradiation source, e.g. laser, is used for a given direction, whereby positioning of the particle in the second direction, if needed, is performed by shifting the optical irradiation source on a slider 254. Such shifting may e.g. be performed in a mechanical way, electrical way, magnetic way etc. although the invention is not limited thereto. An exemplary system 250 according to the second particular embodiment is shown by way of illustration in Fig. 8.

In a further embodiment, the present invention relates to a system 100 for manipulating a particle 104, whereby the system 100 furthermore comprises a handling system 130 whereby the particle 104 is handled or treated. The handling system 130 may be an in vitro treatment, whereby orientation of the particle may be of importance. Such handling system 130 may be a system for injecting material in the particle or extracting material from the particle. Such a handling system 130 may for example be a micro -injection system whereby micro -injection in the particle 104 can be performed under a controlled orientation of the particle. Alternatively or in addition thereto such handling system 130 also may be a system for providing electroporation or bombardment of particles, etc. Some exemplary techniques which may be performed using a system according to the present invention is the transfection of cells and in- vitro fertilization, the invention not being limited thereto. The handling or treatment system 130 is schematically represented in Fig. 1. It is an advantage of embodiments according to the present aspect that orientation of a single particle can be controlled.

In a second aspect, the present invention relates to a characterization system for characterizing a particle wherein a system for individually manipulating a particle is comprised as described in the first aspect. Such a system is shown by way of example in Fig. 9. The characterization system 600 thus comprises a system for individually manipulating a particle 102 as described above and furthermore may comprise a detection system 602 for determining a characteristic of the particle 102. Such a detection system 602 may comprise an excitation system and a detector for exciting the trapped and optionally oriented particle 102 and for detecting a response thereof. Alternatively or in addition to the detector and/or excitation means, the characterization system 600 also may allow optical inspection, e.g. visual inspection, of details of the particles. The detector may e.g. be an optical detector such as e.g. a fluorescence detector, for detecting a fluorescence response from the particle, a magnetic detector, such as e.g. a Hall detector or magneto -resistive detector for detecting magnetic properties. The characterization system 600 also may make use of label-based detection, whereby labels are selectively bound to particles with predetermined characteristics and whereby label detection allows quantification and characterization of particles with such predetermined characteristics. In other words, the characterization system 600 may be used for label detection at particles, e.g. at cell membranes, and/or characterization of properties of such particles 104. The characterization system 600 may be adapted for detecting a particle property for a number of different orientations of the particle, e.g. by providing a number of predetermined orientations to the particle and characterizing or detecting properties thereof for each of the predetermined orientations. The system for manipulating 100 may e.g. be used to check whether a label or other property of interest is not hidden at the back of the particle 104, thus being hidden for characterization or detection. In this way, a qualitative better characterization may be obtained using a characterization system according to the present invention. Besides a detection system 602, the characterization system 600 preferably also comprises a processing means 604 for receiving detection information from the detection system 602 and processing and optionally analyzing the detection information. The processed results may be outputted to the user. Such processing means 604 may process the information in any suitable way, e.g. based on predetermined algorithms, neural networks, etc. and may operate in an automated or automatic way. The characterization system 600 also may be especially useful for studying mechanics of particles 104. Particles 104 typically may have anisotropic mechanical properties. Particle mechanics, such as e.g. cell mechanics, thereby may be of fundamental importance for understanding the working of the particle, e.g. cell. As e.g. cell mechanics may be strongly related to diseases, the characterization system may be used in oncology, e.g. for study or diagnosis of diseases.

In a third aspect, the present invention relates to a system controller 116 for controlling individual manipulation of a particle in a system 100, e.g. as described in the first aspect. The system controller 116 may control the overall operation of a system 100 for individually manipulating a particle 102. The flow generator 108 and the particle manipulator 110 typically may be connected to the system controller 116. Furthermore, the system controller 116 may obtain an input from a feedback system. The system controller 116 according to the present aspect is adapted for controlling the flow generator 108 of a system for generating a laminar flow of the fluid 106 and adapted for controlling the particle manipulator 110 for trapping the particle 104 in the fluid channel 102 and for controlling a shear force on the particle induced by the laminar fluid flow. The latter may be performed by providing predetermined or calculated control signals to the flow generator 108 and particle manipulator 110. Controlling the shear force may be performed by controlling a particle position controller 112 and/or a flow controller 113 controlling the flow generator 108. The system controller 116 also may comprise the flow controller 113, if present, and thus perform its actions. The system controller 116 furthermore may comprise a memory for storing control parameters for controlling the flow generator and the particle manipulator. The controller may include a computing device, e.g. microprocessor, for instance it may be a micro-controller. In particular, it may include a programmable controller, for instance a programmable digital logic device such as a Programmable Array Logic (PAL), a

Programmable Logic Array, a Programmable Gate Array, especially a Field Programmable Gate Array (FPGA). The use of an FPGA allows subsequent programming of the manipulating system 100, e.g. by downloading the required settings of the FPGA. The system controller 116 may be operated in accordance with settable parameters. In a fourth aspect, the present invention relates to a method for individually manipulating a particle 104 in a fluid 106. According to the present aspect, a fluid flow is generated such that a laminar flow of the fluid 106 is obtained in a fluid channel 102. The latter may be performed by passively and/or actively providing a flow of the fluid comprising the particle 104. Actively providing may e.g. be obtained by pumping the fluid 106 through the fluid channel 102. Passively providing a fluid flow may be obtained where a flow is induced under natural forces such as capillary action or gravitational action and whereby control of the flow is provided by controlling a valve, allowing fluid to pass or not to pass. The method furthermore comprises trapping of the particle 104 in the fluid channel 102. The latter may be performed by optically trapping the particle 104, e.g. using optical tweezers, by deforming the fluid channel 102, by applying an acoustic field, by applying a magnetic and/or electric field, etc. The method furthermore comprises controlling a net shear force on the particle 104 induced by the laminar flow. Such controlling may be performed by bringing the particle 104 in a flow field creating a net shear force on the particle 104 or by inducing a shear force gradient on the particle 104 by switching the flow field ON. The latter allows to orient the particle 104, e.g. according to a predetermined orientation. In one embodiment, a method according to the present aspect of the present invention also may comprise handling or treating a particle 104 under a predetermined orientation. Such handling or treating may e.g. be micro-injecting of a particle 104. The method may be especially suitable for being performed using a system 100 as described in the first aspect of the present invention, the functionality of the different components corresponding with possible method steps of the present aspect of the invention.

In a fifth aspect, the present invention relates to a method of characterizing a particle 104 whereby the method comprises the method steps for individually manipulating a particle 104 as described in the fourth aspect, the method furthermore comprising the step of determining a characteristic property of the particle 104. The latter may comprise exciting a particle 104 and detecting a physical response of the particle 104, such as a fluorescence signal, a magnetic response, an electric response, etc. Determining a characteristic property of a particle 104 also may comprise identifying a particle 104 or checking whether a particle 104 belongs to a certain category. Determining a characteristic property of the particle 104 may also comprise determining particle mechanics for the particle 104, as the latter may allow to recognize or detect some diseases. The method of characterizing furthermore may comprise determining a characteristic property of the particle 104 for different orientations of the particle. The latter may e.g. assist in detecting whether certain properties were hidden by the particle 104 for some orientations of the particles, or more generally to increase the reliability of the obtained characterization results. Similar steps and features may further be provided as described in the fourth aspect and as e.g. expressed by the functionality of the components of the first and second aspect of the present invention.

The above-described method embodiments of the present invention may be implemented in a processing system 700 such as shown in Fig. 10. Fig. 10 shows one configuration of processing system 700 that includes at least one programmable processor 703 coupled to a memory subsystem 705 that includes at least one form of memory, e.g., RAM, ROM, and so forth. It is to be noted that the processor 703 or processors may be a general purpose, or a special purpose processor, and may be for inclusion in a device, e.g., a chip that has other components that perform other functions. Thus, one or more aspects of the present invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. The processing system may include a storage subsystem 707 that has at least one disk drive and/or CD-ROM drive and/or DVD drive. In some implementations, a display system, a keyboard, and a pointing device may be included as part of a user interface subsystem 709 to provide for a user to manually input information. Ports for inputting and outputting data also may be included. More elements such as network connections, interfaces to various devices, and so forth, may be included, but are not illustrated in Fig. 10. The various elements of the processing system 700 may be coupled in various ways, including via a bus subsystem 713 shown in Fig. 10 for simplicity as a single bus, but will be understood to those in the art to include a system of at least one bus. The memory of the memory subsystem 705 may at some time hold part or all (in either case shown as 711) of a set of instructions that when executed on the processing system 700 implement the steps of the method embodiments described herein. Thus, while a processing system 700 such as shown in Fig. 10 is prior art, a system that includes the instructions to implement aspects of the methods for manipulating particles or characterizing particles is not prior art, and therefore Fig. 10 is not labeled as prior art.

The present invention also includes a computer program product which provides the functionality of any of the methods according to the present invention when executed on a computing device. Such computer program product can be tangibly embodied in a carrier medium carrying machine-readable code for execution by a programmable processor. The present invention thus relates to a carrier medium carrying a computer program product that, when executed on computing means, provides instructions for executing any of the methods as described above. The term "carrier medium" refers to any medium that participates in providing instructions to a processor for execution. Such a medium may take many forms, including but not limited to, non-volatile media, and transmission media. Non volatile media includes, for example, optical or magnetic disks, such as a storage device which is part of mass storage. Common forms of computer readable media include, a CD-ROM, a DVD, a flexible disk or floppy disk, a tape, a memory chip or cartridge or any other medium from which a computer can read. Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to a processor for execution. The computer program product can also be transmitted via a carrier wave in a network, such as a LAN, a WAN or the Internet. Transmission media can take the form of acoustic or light waves, such as those generated during radio wave and infrared data communications. Transmission media include coaxial cables, copper wire and fiber optics, including the wires that comprise a bus within a computer.

It is an advantage of particular embodiments of the present invention that these can be advantageously used in study of particles, such as e.g. study of cells. It is also an advantage of particular embodiments of the present invention that the methods can be used in the fields of medicine and cell science.

It is an advantage of particular embodiments of the present invention that the orientation of a single cell can be determined.

It is to be understood that although preferred embodiments, specific constructions and configurations, as well as materials, have been discussed herein for devices according to the present invention, various changes or modifications in form and detail may be made without departing from the scope and spirit of this invention.

Claims

CLAIMS:

1. A system (100) for individually manipulating a particle (104) in a fluid (106), the system (100) comprising: a flow generator (108) adapted for generating a laminar fluid flow of the fluid (106) in a fluid channel (102), and - a particle manipulator (110) adapted for trapping and orienting the particle

(104) in the fluid channel (102) by controlling a net shear force induced by the laminar fluid flow on the particle (104).

2. A system (100) according to claim 1, wherein the particle manipulator (110) comprises a particle position controller (112) for controlling a position of the particle (104) in a direction substantially perpendicular to a flow direction of the laminar fluid flow.

3. A system (100) according to claim 2, wherein the particle position controller (112) is adapted for moving the particle (104) to a predetermined position in the fluid channel

(102) where a predetermined net shear force on the particle is induced by the laminar flow.

4. A system (100) according to any of claims 1 to 3, wherein a shape of the fluid channel (102) is adapted such that the fluid channel (102) comprises at least one position in a trapping region for the particle wherein no net shear force acts on the particle (104) when a laminar flow is present.

5. A system (100) according to any of claims 1 to 4, wherein the particle manipulator (110) adapted for controlling a net shear force induced by the laminar fluid flow on the particle (104) is adapted for controlling an intensity of the laminar fluid flow generated by the flow generator (108).

6. A system (100) according to any of claims 1 to 5, wherein the particle manipulator (110) comprises a flow controller (113) for controlling an intensity of the laminar fluid flow generated by the flow generator (108).

7. A system (100) according to any of claims 1 to 6, wherein said particle manipulator (110) comprises at least one optical tweezer (202, 204, 252).

8. A system (100) according to any of claims 1 to 7, wherein said particle manipulator (110) comprises at least one dielectrophoretic trap.

9. A system (100) according to any of claims 1 to 8, the system (100) further comprising a feedback system (114) for determining a position and orientation of a particle and for providing feedback control signals to the particle manipulator (110).

10. A system (100) according to any of claims 1 to 9, the system (100) further comprising a handling system (130) adapted for injecting material in and/or extracting material out of the particle (100) under a predetermined orientation of the particle (100).

11. A system (100) according to any of claims 1 to 10, wherein the flow generator (108) is adapted for providing a maximum flow velocity of the laminar fluid flow between 0 m/s and 10^"3 m/s.

12. A system (100) according to any of claims 1 to 11, wherein the system is adapted for individually manipulating biological cells.

13. A characterization system (600) for charactering a particle, the particle characterization system (600) comprising a system (100) for individually manipulating a particle (104) in a fluid (106) according to any of claims 1 to 12, and the characterization system (600) furthermore adapted for determining a characteristic property of the particle (104).

14. A characterization system according to claim 13, the characterization system comprising a detection means for detecting a magnetic or optical property of the particle or of a label bound to the particle.

15. A method for individually manipulating a particle (104) in a fluid (106), the method comprising generating a laminar fluid flow of the fluid (106) in a fluid channel (102), - individually trapping the particle (104) in the fluid channel (102), and orienting the particle by controlling a net shear force induced by the laminar fluid flow on the particle (104).

16. A method for individually manipulating a particle (104) according to claim 15, wherein orienting the particle comprises controlling the orientation or rotation of the particle by changing a position of the particle in a flow field of the laminar flow of the fluid (106) and/or by changing a velocity distribution in a flow field of the laminar flow of the fluid (106).

17. A method for characterizing a particle (104) in a fluid (106) comprising individually manipulating the particle (104) according to a method of any of claims 15 to 16 such that a predetermined orientation of the particle is obtained, and determining a property of the particle under the predetermined orientation.

18. A controller for use in a system for individually manipulating a particle (104) in a fluid (106) as described in any of claims 1 to 12.

19. A computer program product for, when executed on a computing means, performing a method for individually manipulating a particle (104) in a fluid (106), the method comprising: generating a laminar fluid flow of the fluid (106) in a fluid channel (102), individually trapping the particle (104) in the fluid channel (102), and orienting the particle by controlling a net shear force induced by the laminar fluid flow on the particle (104).

20. A machine readable data storage device storing the computer program product of claim 19.

21. Transmission of the computer program products of claim 19 over a local or wide area telecommunications network.