HK1068841B - Optical peristaltic pumping with optical traps - Google Patents

Description

Optical peristaltic pumping with optical traps

Technical Field

The present invention relates generally to methods and apparatus for controlling and manipulating small particles, moving masses or deformed structures. More particularly, the present invention relates to methods and apparatus for controlling and manipulating particles and bulk materials using holographic optical traps in accordance with general and complex methods.

Background

Preferably, the optical traps use optical gradient forces to trap two and three dimensional microscale large quantities of matter. Holographic forms of optical trapping can utilize computer generated diffractive optical elements to create a large number of optical traps from a single laser beam. The optical traps may be arranged in any desired configuration depending on the current needs.

While systems for moving particles with precision and relatively high confidence are well known, conventional systems require the projection of a separate hologram for each discrete step of particle motion. Computing multiple holograms is very time consuming and requires a considerable computational effort. Furthermore, the computer-addressable projection systems required to implement such computer-generated optical traps or other dynamic optical trap systems, such as scanning optical clamps, tend to be very expensive.

Disclosure of Invention

It is therefore an object of the present invention to provide an improved method for manipulating particles and bulk materials according to general methods and complex methods.

It is a further object of the invention to provide an improved method of moving particles along a predetermined path with high accuracy and confidence.

It is a further object of the invention to provide a method for manipulating particles and bulk materials that eliminates the computational burden of implementing complex rearrangements.

In accordance with the above objectives, dynamic reconfiguration of the optical traps can be achieved by projecting a time-varying sequence of such patterns of optical traps, wherein each new pattern updates the position of each optical trap by a distance sufficiently small so that the particles trapped in the original pattern naturally fall into the corresponding optical trap in the next pattern. Therefore, the present invention provides a method for accomplishing complex realignment of materials using a small number of pre-computed holographic optical trap patterns that are cycled through. The recycling can be achieved mechanically, thereby eliminating the computational complexity and expense of a general purpose holographic optical trap system.

The invention provides a method for transferring particles between optical trapping clusters, which comprises the following steps:

providing a laser beam;

dividing the laser beam into a plurality of auxiliary laser beams;

focusing the assist laser beam to create a plurality of optical traps;

providing a first pattern comprising a plurality of sequentially arranged clusters, a second pattern and a third pattern, each cluster comprising at least one optical trap of a laser beam, wherein the first pattern, the second pattern and the third pattern are arranged such that the clusters constituting each pattern are separated by the clusters of each other pattern; and

after extinguishing the previous pattern, each pattern is sequentially illuminated and extinguished with a laser beam spaced sufficiently close together to capture and transfer particles from one cluster to an adjacent cluster, wherein the capture and transfer of particles causes the particles to be transported from one cluster on the pattern to an adjacent cluster on the same pattern.

The present invention also provides a method of manipulating a plurality of particles with a laser beam, comprising the steps of:

providing a laser beam;

dividing the laser beam into a plurality of auxiliary laser beams;

focusing the assist laser beam to create a plurality of optical traps;

providing a plurality of interleaved patterns, each interleaved pattern comprising at least one cluster, each cluster comprising at least one optical trap for the laser beam, the cluster being positioned adjacent to clusters in other patterns;

after extinguishing the previous pattern, each pattern is sequentially illuminated and extinguished with a laser beam sufficiently closely spaced to capture a particle of the plurality of particles that is transported from a cluster on one pattern to an adjacent cluster.

The present invention provides an apparatus for manipulating a plurality of particles, comprising:

a laser beam divided into a plurality of auxiliary laser beams, the plurality of optical traps being created by the auxiliary laser beams;

a first pattern, a second pattern, and a third pattern comprising a plurality of sequentially spaced clusters, each cluster including an optical trap formed by a laser beam, wherein the first pattern, the second pattern, and the third pattern are arranged such that the clusters in each pattern are separated by the clusters in each other pattern; and

means for sequentially illuminating and extinguishing each pattern, after extinguishing a previous pattern, by sequentially illuminating and extinguishing each pattern with a laser beam spaced sufficiently close together to capture and transfer particles from one cluster to the next adjacent cluster, and wherein the capture and transfer of particles causes the particles to be transferred from one cluster on a first pattern to another cluster on the same pattern.

The present invention also provides a method of transferring particles between clusters of a deterministic light gradient, comprising the steps of:

providing a laser beam;

focusing the laser beam to establish a plurality of deterministic light gradients;

providing a first pattern comprising a plurality of sequentially arranged clusters, a second pattern and a third pattern, each cluster comprising at least one optical gradient of the laser beam, wherein the first pattern, the second pattern and the third pattern are arranged such that the clusters constituting each pattern are separated by clusters on each other pattern; and

after extinguishing the previous pattern, each pattern is sequentially illuminated and extinguished with a laser beam spaced sufficiently close to capture and transfer individual particles from one cluster to an adjacent cluster, wherein the capture and transfer of each particle is a transfer of each particle from one cluster on one pattern to an adjacent cluster on the same pattern.

Drawings

FIG. 1 depicts a single particle trapped in an optical trap within a cluster of optical traps, where the dashed line indicates the location of the cluster (manifold);

FIG. 2 illustrates the transfer of a single particle from a cluster of optical traps in a first pattern to a cluster of optical traps in a second pattern;

FIGS. 3A-3D illustrate the operation of the optical peristalsis (peristalsis) method;

FIG. 4 illustrates the use of parallel linear clusters of optical traps to transfer particles along linear trajectories perpendicular to the clusters;

FIG. 5A shows a curved cluster directing particles from around the pattern toward the center of curvature; and FIG. 5B shows how the pattern depicted in FIG. 5A can sweep the particle entry channel;

FIG. 6A shows a non-uniformly curved cluster separating a particle stream into two separate particle streams; and figure 6B shows a non-uniformly curved cluster combining two separate particle streams into a single larger particle stream;

FIG. 7A shows multiple concentric circular clusters transporting particles away from a region; and FIG. 7B conveys particles into multiple concentric circular clusters of a region;

FIG. 8 is a graph showing the movement of two particles in response to the application of an external field and a light peristalsis pattern;

FIG. 9 shows a two-stage light separation with particles of a first type traveling to the right and particles of a second type traveling to the left;

FIG. 10 illustrates the use of dynamic holographic optical traps to achieve optical peristalsis;

FIG. 11 shows a dynamic holographic optical trap system using a transmission mode computer addressed spatial light modulator in an optical path system;

FIG. 12 shows mechanically cycling a series of static computer-generated diffractive optical elements;

FIG. 13 shows a mechanical recycling light peristalsis system using computer-generated transmissive diffractive optical elements arrayed around a disk;

FIG. 14 shows multiple clusters of optical traps trapping an extended object and rotating the object; and

FIG. 15 shows trapping of an expanded deformed object using a cluster of light traps.

Detailed Description

Optical peristalsis involves the use of projecting a pre-computed sequence of holograms over a period of time to achieve complex redistribution of a large number of particles over a large or selected area. An important aspect of the optical peristalsis of the present invention is the non-specific transfer of particles from one cluster of optical traps in a given pattern to the next pattern through at least two intermediate patterns. The term "graphic" means to include at least one cluster. Fig. 1 shows a cluster 20 of optical traps 24 arranged along a straight line. Each optical trap 24 is capable of trapping a desired particle 22 and the optical traps 24 are spaced apart from one another so that the particle 22 is less likely to be transported through the cluster 20 without falling into an existing one of the optical traps 24 or being blocked by an existing particle in the optical trap 24. The particles 22 are depicted as spheres but may be irregularly shaped or even be much larger than the spacing between the light traps 24.

The optical peristalsis operates by extinguishing the cluster 20 of optical traps 24 to release the particle 22 for movement. If another pattern of optical traps 24 is illuminated in sufficient proximity, the particle 22 is trapped by the optical trap(s) 24 in the new pattern. In the case shown in fig. 3A-3D, the pattern comprises two clusters 20 on lines 23 and 25. However, the next pattern contains only one cluster, e.g. along the cluster on line 27. In effect, particles 22 are transferred from one cluster 20 of optical traps 24 in a first pattern 26 to another cluster 20 in a second pattern 28. Fig. 2 shows the simplest form of this process, while fig. 3A-3D show the more general case. To effect the transfer of particles 22, the first pattern 26 may be first extinguished; the second pattern 28 is then illuminated, provided that the separation between the two patterns 26 and 28 is sufficiently short to prevent the trapped particle 22 from "drifting" (light gradient) before being trapped by the nearest neighbor of one of the optical traps 24. Illuminating the second graphic 28 before extinguishing the first graphic 26 is also another possible embodiment, but the operation carried out is more complex.

The pattern of optical traps may therefore comprise one or more clusters 20 of discrete optical traps 24, such as discrete clamps (tweezers) in one embodiment of the invention. Each cluster 20 may contain several optical traps 24 arranged along a one-dimensional curve or line, as shown in fig. 1, or on a two-dimensional surface, or within a three-dimensional volume. The concept of a pattern of optical traps consisting of a collection of clusters 20 is useful for viewing the optical peristalsis process.

Fig. 3A shows in more detail one particle 22 captured on one cluster 20 of a particular pattern, which is labeled as a first pattern 26. The first pattern includes two clusters 50 and 56. The locations of the captured clusters 52 and 54 in the second extinguished pattern 28 (this pattern has only one cluster) and the third extinguished pattern 30 (has only one cluster) are also shown. In a first time step only the first graphic 26 is illuminated. At the next time step represented in fig. 3B, the first graphic 26 is extinguished and the second graphic 28 is illuminated. This action transfers particles 22 from a first cluster 50 of first pattern 26 to an adjacent cluster 52 of second pattern 28. At the next time increment step represented in fig. 3C, the second pattern 28 is extinguished and the third pattern 30 is illuminated, thereby again transferring the particles 22, now to the clusters 54 on the third pattern 30. At the last time step represented in fig. 3D, the third graphic 30 is extinguished and the first graphic 26 is illuminated again. This transfers particles 22 to the first pattern 26 on the next cluster 56. Optical peristalsis is therefore produced by deterministically transferring a particle 22 from one cluster 20 on the pattern of optical traps to another cluster 20 on the same second pattern 28 by a sequence of (cyclic) intermediate patterns.

In the most preferred embodiment of the invention, a minimum of three patterns 26, 28 and 30 are required to deterministically advance a particle 22 from one cluster 50 to the next 52 on a capture pattern. If only two equally spaced patterns 26 and 28 are used, there is a high probability that the particle 22 may proceed to the next cluster 52 or return to the original cluster 50. In other embodiments, a pattern of more than three patterns 26, 28, and 30 may be used to transfer particles 22 in a particular direction. Methods of illuminating and extinguishing the individual clusters 20 of light traps 24 are well known to those skilled in the art.

Repeatedly cycling through the first pattern 26, the second pattern 28, and the third pattern 30, respectively, may cause the particles 22 to move from left to right in the arrangement shown in fig. 3. The reverse order may drive the particles from right to left. A more expanded pattern is made up of multiple clusters 20, so that particles 22 can be transferred back and forth across the field of view of the holographic optical trap system.

The rearrangement of the collection of particles 22 may be accomplished using various methods of optical peristalsis. These methods include: the shape of the continuous curve of the clusters 20 is varied within the pattern of optical traps 24. Although a single pattern is described in detail herein, other intermediate patterns needed to transfer between clusters 20 will be readily apparent and appreciated by those skilled in the art. In the examples described herein, the direction of particle flow is indicated by the repeated arrows.

Figure 4 shows a graph 26 of a linear optical peristaltic pump 33. Two or more patterns (not shown) that intersect between each cluster 20 in this pattern 26 may be activated sequentially to drive one or more trapped particles 22 from left to right. Reversing the order may transfer particles 22 from right to left. This graphic, and all of the graphics described herein, may be oriented in any desired direction.

Fig. 5A and 5B show that a pattern of curved clusters 20 can be used to concentrate the particle stream. Conversely, running the sequence in the opposite direction may diffuse the particles 22. This ability can be used to guide particles 22 out of an open area and into a closed area, e.g., a reservoir. The individual tufts 20 need not have equal curvature, and varying the curvature may be useful in certain situations. For example, a straight pumping pattern may be used to sweep the particles 22 into a focusing mode. The respective spacings between two clusters 20 need not be equal. The patterned area with densely packed clusters 20 transfers particles 22 more slowly than sparsely packed clusters 20. Densely packed clusters 20 tend to concentrate particles 22 in the direction of motion, while sparsely packed clusters 20 may be used to spread particles 22. This approach is particularly beneficial for focusing patterns, which avoids excessive crowding of the particles 22 in the concentration.

The distribution and density of optical traps 24 along the clusters can also be used to control the flow of particles 22 between clusters 20. For example, the optical traps 24 may be evenly spaced along each cluster 20 and aligned from one cluster 20 to the next and from one pattern to the next. In other embodiments, there is a more complex arrangement of optical traps 24 along the cluster 20 and between the two patterns, which can be used to control the flow of particles 22 along the sequence of patterns. Similarly, varying the intensity and spacing of individual optical traps 24 along the clusters 20 in the pattern is also useful for controlling the transport of the particles 22.

Shaped clusters 20 that direct the flow of particles 22 may also be used to direct particles 22 into any desired complex pattern. The example shown in fig. 6A shows a shaped cluster 20 that separates a particle stream 22 into two particle streams. Such a pattern can be used to combine two (or more) particle streams into one particle stream when traveling in opposite directions. While this approach is not very effective because once the clusters 20 are combined, the particles 22 in one particle stream remain adjacent to other particles in the same particle stream, it is still beneficial.

The example shown in fig. 6B illustrates one method of inducing mixing of particles 22 in a combined particle stream. This example illustrates that the clusters 20 in the pattern need not be separate. The pattern in this system contains cross-form clusters 20 in the mixing zone. Such crossover may be used to exchange particles 22 between the initially distinct particle streams. Crossing or intersecting simple clusters 20 to form more complex clusters 20 introduces statistical elements to the optical peristalsis. A choice of one transport direction is given to the particles 22 in the vicinity of each intersection. Which direction each particle 22 takes is determined by the random heating power at the transition from one pattern to the next in the sequence. Thus, the intersection shown in FIG. 6B may result in some degree of mixing.

Fig. 7A and 7B illustrate an example where a pattern of closed-form clusters 20 can transport particles 22 into or out of a region. Whether the graph is a dense or sparse region depends on the order in which the sequence of graphs is projected. The example of fig. 7A is used to remove particles 22 from a region, for example, to facilitate testing of a suspension fluid or measurement of isolated particles 22. Such a pattern need not be circular and need not be limited to a planar pattern. In principle, two-dimensional form clusters 20 in a three-dimensional figure can be used to draw material into a volume or push material out of a volume.

Further, it should be noted that competition between light trapping and other external forces is also useful. For example, competition between optical trapping and other external forces is particularly useful for separating particles 22 from a distribution. As an example, consider particles 22 suspended in a surrounding fluid. Each particle 22 is transported by viscous drag in the local flow field u (r), and the drag force f ═ γ u is determined by its drag coefficient γ. For a small sphere of radius a in the viscous fluid η, the drag coefficient γ is given by the formula γ ═ 6 π η a and increases linearly with the radius of the particle. The force required for the larger particles to remain stable against flow is greater than the force required for the smaller particles. Although viscous drag is an example of an external force, other external forces such as an electric or magnetic field are also encompassed by the description herein

Examples are given.

If the external force is less than the optical gradient force of a given one of the optical traps 24, the movement of the particles 22 conveyed by the optical peristalsis is greater, as described above. If the external force is greater than the optical gradient force of the optical trap 24, the optical peristalsis can only interfere with the movement of the particle 22 in the external field. In the ideal example shown in fig. 8, one type of particle 22 is more strongly attracted to the optical trap 24 than in the case of external field driving. In the example shown in fig. 8, the first particles 60 are more easily trapped or less affected by the external field than the second particles 62. Therefore, the first particles 60 are peristaltically transported by the light and may be collected. The second particle 62 is more strongly driven by the external field and is transported through the pattern of optical traps 24, perhaps diverted to some extent from its original path.

The two types of particles 60 and 62 in the embodiment shown in fig. 8 differ either by their affinity for the optical trap 24 or by their response to an external field, or both. The particles can be separated by selecting the spatial distribution, intensity and other characteristics of the light traps 24 in the pattern, the selectivity of which is determined by the different physical characteristics of the particles.

Light separation techniques have a number of significant advantages. Light separation occurs in the direction along the applied field in electrophoresis. The light separation may laterally transmit selected portions. This means that the light separation can be run continuously, rather than batch at a time. Since the light separation depends on holographic light trapping technology, it can easily be adapted to different separation problems.

For example, with the same method and apparatus, multiple levels of light separation can be applied sequentially. Tuning each stage to extract a particular ratio of the initially mixed multi-component samples, the samples can be divided into each of the multiple components, thereby conveniently laterally displacing the classified components from the flow, perhaps using the techniques described above, to deliver them to the respective channel or reservoir.

The embodiment in fig. 9 includes a second stage of light separation to create a single separation stage. The external force that drives the particles 22 through this region is directed downward. The first pattern, labeled 80 in fig. 9, picks particles of the first type 84 and moves them to the right, but does not collect particles of the second type 86. The second stage of separation, labeled as portion 82, is characterized by stronger or more densely packed optical traps 24 that are capable of diverting the second type 86 of particles 22 away from the external force. As shown in fig. 9, this second level of graphics 82 is propagated to the left, still further increasing the separation between portions 84 and 86. Although conceptually independent, the two levels of separation may be a single pattern of clusters of optical traps 20. This process can be generalized to include multiple stages and to merge and transfer separated particles for collection.

As described above, the optical peristalsis operation is a sequence of repeated cycles through the pattern of optical traps. The dynamic holographic systems schematically shown in fig. 10 and 11 are generic implementations. In this case, the computer-addressable spatial light modulator 102 establishes the configuration of the laser beam 104 required to implement a given pattern of optical traps 114 by encoding the required phase modulation onto the wavefront of the input laser beam 100. In principle, such a system can implement any sequence of patterns of light traps, and therefore, any pattern of optical peristalsis. In practice, however, the spatial light modulator 102 has physical limitations, e.g. spatial resolution, which limits the complexity of the coding pattern. Furthermore, the cost of such spatial light modulators 102 tends to be high.

In the embodiment shown in FIG. 10, optical peristalsis can be accomplished using a dynamic holographic optical trap 114, with FIG. 10 being an exemplary implementation. An input laser beam 100 is reflected from the surface of a computer-addressable Spatial Light Modulator (SLM) 102. SLM 102 encodes a computer generated phase shift pattern onto the wavefront of laser beam 100 to split the beam into one or more individual laser beams 104, each laser beam 104 emerging from a central point 107 on the face of SLM 102. Lenses 108 and 110 relay each of these laser beams 104 to a conjugate point at the center of the back aperture of high NA objective lens 112. This objective lens 112 focuses each laser beam 104 to a separate optical trap 114, only one of which is shown in fig. 10 for simplicity. Dichroic mirror 116 reflects the capture light to objective 112, while allowing the imaging illumination light to pass through, so that an image is formed by the captured particles. Updating the phase modulation encoded by the SLM 102 can create a new pattern of optical traps 114. In this way, a sequence of light creep patterns is cycled through to achieve a corresponding light creep process. Since this system can be reconfigured using software, it represents a general implementation of optical peristalsis. In another embodiment shown in FIG. 11, a dynamic holographic optical trap system utilizes a transmissive mode computer addressable spatial light modulator 200 in the optical path, with other configurations similar to FIG. 10. This system can also be used to achieve optical peristalsis by cycling through a sequence of capture patterns.

Achieving optical peristalsis does not necessarily require the versatility and reconfiguration capabilities provided by dynamic holographic optical trap systems. Instead, optical peristalsis is best achieved using a holographic optical trap system capable of projecting a sequence of (small) static patterns. In its simplest preferred form, optical peristalsis can be achieved by mechanically cycling through a sequence of phase patterns to achieve a corresponding sequence of holographic optical trap patterns. Figure 12 shows a particularly useful embodiment. As shown in fig. 12, the phase pattern required to achieve a particular optical peristalsis process is encoded in the surface relief of the reflective diffractive optical elements 304, 306 and 308. These optical elements 304, 306 and 308 are mounted to the surface of the prism 300, each of which is rotated into position by a motor 302. Reversing the motor reverses the sequence of patterns and thus reverses the direction of light creep. The prism 300 is rotated by motor 302 to direct each pattern against the incoming laser beam so that the diffracted beams produced by the aligned diffractive optical elements 304, 306 and 308 create the optical traps 114. The optical peristalsis can be achieved by advancing the motor 302 stepwise through each pattern in sequence. Prisms having more than three patterns can be used if desired.

Mounting a series of fixed reflective diffractive optical elements 304, 306 and 308 on the surface of the rotating prism 300 can have other uses in holographic optical trapping methods. Similarly, transmissive diffractive optical elements 404, 406, 408 and 410 may be placed around the disk 312 and rotated into the beam 100 as shown in FIG. 13 or as a continuous pulse of reflected light. This situation has potential applications in addition to optical peristalsis. For example, in FIG. 13, each diffractive optical element 404, 406, 408, and 410 is rotated to form successive light pulses so that a pattern in a peristaltic sequence of light can be projected.

It is possible to manufacture a static reflection type or transmission type diffractive optical element whose characteristic size is reduced to the diffraction limit, which can have a substantially continuous phase encoding, and therefore, various trapping patterns more complicated than the spatial light modulator can be realized. Such components can be produced at very low cost and do not require the use of a computer for operation. The sequence of patterns in such a system can be changed by changing the prism or the disk of the diffractive optical element. In this sense, such an implementation is not as versatile as an implementation based on computer-addressable spatial light modulators.

Exchangeable phase gratings may also be utilized, since only a small number of pre-calculated diffractive optical elements are required to achieve optical peristalsis. Advantages of this approach are, for example, no moving parts that may become misaligned and worn, no motors that may cause vibrations and radiate stray electric and magnetic fields, and reduced power requirements and volume.

Encoding a high quality phase hologram on a thin film medium can achieve optical peristalsis comparable to that on a sheet loop. Allowing high-speed cycling through a large number of diffractive optical elements, the substrate-based holographic optical trap implementing apparatus may have applications other than optical peristalsis.

Optical peristalsis can also be used for particles and other substances, e.g., biological cells, that are larger than the actual spacing between the individual optical traps in the optical peristalsis pattern. Similarly, materials such as proteins, DNA or molecules can also be manipulated using optoperistaltic action. By translating the bed of nails (bed of nails), it is still possible to move the bed of nails to optically capture large objects captured on the graphic. However, rather than defining a single trapping region, the optical peristalsis pattern can create a large trapping field suitable for holding large objects found anywhere. As described above, updating the pattern with a small displacement makes it possible to displace the entire object. Potential applications include: translating the expanded sample to an area where it can be tested, rotating the inspected object, or controllably deforming the object. For example, in the embodiment of fig. 14, fig. 14 shows the optical trapping cluster 20 trapping the extended object 80. Updating the pattern with clusters 20 tends to rotate the expanded object 80. Similarly, FIG. 15 shows the optical trapping cluster 20 trapping the extended anamorphic object 82. The object 82 is strongly trapped by the denser regions of optical trapping and moving these regions outward in subsequent patterns can stretch the object 82.

Each optical peristalsis sequence performs a specific operation. In some applications, it is required to perform a series of optical peristalsis operations, the order of which depends on the results of the previous operations. For example, optical peristalsis can be used to move living cells into the center of the microscope's field of view for reproducible viewing. The second sequence can then rotate the cell to the desired orientation. The third sequence may then perform a specific test. Based on the results of this test, additional light peristaltic sequences may be selected to collect cells or for processing. Each of these sequences can be pre-computed, thereby eliminating much of the computational burden in holographic optical trap systems. Similarly, different sub-sequences of optical peristalsis operations can be combined into a single procedure, where a first sub-sequence can separate particles into two or more distinct particle streams, a second sub-sequence can disperse particles from a particular location, a third sub-sequence can mix two separate particle streams into a single particle stream, a fourth sub-sequence can concentrate multiple particles into a particle region, and various other methods can also be used to "move" particles from one pattern to another. Various combinations of the subsequences described above can be combined into a single program, and using the various types of optical gradients described herein, the subsequences can be used sequentially and/or simultaneously as desired. Since very few diffractive optical elements are required to implement any one sequence, only moderate considerations need to be taken into account in the proposed implementation to choose among the set of available sequences for such multi-stage operation.

Furthermore, the invention may also be practiced without the use of conventionally understood optical traps, and may require specific optical gradients to control particles. For example, multiple deterministic light gradients can be established and incorporated into the multiple clusters and patterns described above. The role of these deterministic optical gradients is to "steer" or suppress individual particles in a particular location in sequence long enough to produce an optical peristalsis effect without the necessity of forming optical traps. In other words, repeatedly cycling through the deterministic light gradients of the first, second and third patterns may cause each particle to move along a specified path. Deterministic light gradients mean that the conditions applied are sufficient to achieve the desired result, not just the probability of success.

While we have shown and described the preferred embodiments of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the invention in its broader aspects and as set forth in the following claims.

Claims (34)

1. A method of transferring particles between clusters of optical traps, comprising the steps of:

providing a laser beam;

dividing the laser beam into a plurality of auxiliary laser beams;

focusing the assist laser beam to create a plurality of optical traps;

providing a first pattern comprising a plurality of sequentially arranged clusters, a second pattern and a third pattern, each cluster comprising at least one optical trap of a laser beam, wherein the first pattern, the second pattern and the third pattern are arranged such that the clusters constituting each pattern are separated by the clusters of each other pattern; and

after extinguishing the previous pattern, each pattern is sequentially illuminated and extinguished with a laser beam spaced sufficiently close together to capture and transfer particles from one cluster to an adjacent cluster, wherein the capture and transfer of particles causes the particles to be transported from one cluster on the pattern to an adjacent cluster on the same pattern.

2. The method of claim 1, wherein the clusters in each pattern are aligned substantially parallel to each other, and wherein the transport of the particles follows a substantially straight trajectory perpendicular to the clusters in each pattern.

3. The method of claim 1, wherein the clusters in each pattern have a radius of curvature, and wherein the transport of the particles generally follows a trajectory toward the center of curvature of each cluster.

4. The method of claim 1, wherein the transfer of the plurality of particles is across each cluster.

5. The method of claim 4, wherein each cluster is arranged in a concentric circle manner to concentrate a plurality of particles to a specific region or to scatter a plurality of particles from a specific region.

6. The method of claim 4, further comprising the steps of: applying an external field to each particle of the plurality of particles, wherein each pattern is sequentially illuminated and extinguished using the laser beam, thereby changing the direction of at least some of the particles relative to the direction the particles would take in the presence of only the external field.

7. A method according to claim 6, wherein the effect of the applied field is that the direction of at least some of the particles is not changed as they travel from one cluster to the next immediately adjacent cluster.

8. The method of claim 4, wherein the particles are part of a mass greater than the actual spacing between optical traps on each cluster, and wherein movement of the particles from one cluster to the next immediately adjacent cluster causes actual deformation of the mass.

9. The method of claim 4, wherein the particles are part of a mass greater than the actual spacing between optical traps on each cluster, and wherein movement of the particles from one cluster to the next immediately adjacent cluster results in actual rotation of the mass.

10. The method of claim 1, wherein the particles comprise a portion of a biological medium.

11. A method of manipulating a plurality of particles with a laser beam, comprising the steps of:

providing a laser beam;

dividing the laser beam into a plurality of auxiliary laser beams;

focusing the assist laser beam to create a plurality of optical traps;

providing a plurality of interleaved patterns, each interleaved pattern comprising at least one cluster, each cluster comprising at least one optical trap for the laser beam, the cluster being positioned adjacent to clusters in other patterns;

after extinguishing the previous pattern, each pattern is sequentially illuminated and extinguished with a laser beam sufficiently closely spaced to capture a particle of the plurality of particles that is transported from a cluster on one pattern to an adjacent cluster.

12. The method of claim 11, wherein the plurality of particles comprises at least a portion of a biological medium.

13. The method of claim 11, wherein the plurality of particles are larger than the actual spacing between the respective optical traps on each cluster, and wherein movement of the particles across each cluster results in actual rotation of the plurality of particles.

14. The method of claim 11, wherein the plurality of particles are larger than the actual spacing between the individual optical traps on each cluster, and wherein movement of each particle across each cluster results in actual deformation of the plurality of particles.

15. The method of claim 11, wherein each cluster is aligned substantially parallel to each other, and wherein the transport of the plurality of particles follows a substantially linear trajectory perpendicular to each cluster.

16. The method of claim 11, wherein each cluster has a radius of curvature, and wherein the plurality of particles travel substantially along a trajectory toward a center of curvature of each cluster.

17. An apparatus for manipulating a plurality of particles, comprising:

a laser beam divided into a plurality of auxiliary laser beams, the plurality of optical traps being created by the auxiliary laser beams;

a first pattern, a second pattern, and a third pattern comprising a plurality of sequentially spaced clusters, each cluster including an optical trap formed by a laser beam, wherein the first pattern, the second pattern, and the third pattern are arranged such that the clusters in each pattern are separated by the clusters in each other pattern; and

means for sequentially illuminating and extinguishing each pattern, after extinguishing a previous pattern, by sequentially illuminating and extinguishing each pattern with a laser beam spaced sufficiently close together to capture and transfer particles from one cluster to the next adjacent cluster, and wherein the capture and transfer of particles causes the particles to be transferred from one cluster on a first pattern to another cluster on the same pattern.

18. The apparatus of claim 17, wherein the particles are part of a plurality of particles larger than the actual spacing between optical traps on each cluster, and wherein movement of the particles from one cluster to the next immediately adjacent cluster results in actual deformation of the plurality of particles.

19. The apparatus of claim 17, wherein the particles are part of a plurality of particles larger than the actual spacing between optical traps on each cluster, and wherein movement of the particles from one cluster to the next immediately adjacent cluster results in actual rotation of the plurality of particles.

20. The apparatus of claim 17, wherein the direction of a particle as it travels from one cluster to the next immediately adjacent cluster is changed by an external field applied to the particle.

21. The apparatus of claim 17, wherein the direction of the particle as it travels from one cluster to the next immediately adjacent cluster is not altered by an external field applied to the particle.

22. The apparatus of claim 17, wherein the particles comprise a portion of the biological medium.

23. The apparatus of claim 17, wherein the clusters in each pattern are aligned substantially parallel to each other, and wherein the transport of the particles follows a substantially linear trajectory perpendicular to the clusters in each pattern.

24. The apparatus of claim 17, wherein the clusters in each pattern have a radius of curvature, and wherein the transport of the particles generally follows a trajectory toward a center of curvature of each cluster.

25. The apparatus of claim 17, wherein the plurality of clusters are arranged such that sequentially illuminating and extinguishing each pattern divides the plurality of particles into at least two groups of particles.

26. The apparatus of claim 17, wherein the plurality of clusters are arranged such that sequentially illuminating and extinguishing each pattern combines a plurality of particles into a single set of particles.

27. A method of transferring particles between clusters of a deterministic light gradient, comprising the steps of:

providing a laser beam;

focusing the laser beam to establish a plurality of deterministic light gradients;

providing a first pattern comprising a plurality of sequentially arranged clusters, a second pattern and a third pattern, each cluster comprising at least one optical gradient of the laser beam, wherein the first pattern, the second pattern and the third pattern are arranged such that the clusters constituting each pattern are separated by clusters on each other pattern; and

after extinguishing the previous pattern, each pattern is sequentially illuminated and extinguished with a laser beam spaced sufficiently close to capture and transfer individual particles from one cluster to an adjacent cluster, wherein the capture and transfer of each particle is a transfer of each particle from one cluster on one pattern to an adjacent cluster on the same pattern.

28. The method of claim 27, wherein the plurality of particles is larger than the actual spacing between the respective optical gradients on each cluster, and wherein movement of each particle across each cluster results in actual rotation of the plurality of particles.

29. The method of claim 27, wherein the plurality of particles is larger than the actual spacing between the respective optical gradients on each cluster, and wherein movement of each particle across each cluster results in actual deformation of the plurality of particles.

30. The method of claim 27, wherein the plurality of clusters are arranged such that sequentially illuminating and extinguishing each pattern divides the plurality of particles into at least two groups of particles.

31. The method of claim 27, wherein the plurality of clusters are arranged such that sequentially illuminating and extinguishing each pattern combines a plurality of particles into a single set of particles.

32. The method of claim 27, wherein at least some of the plurality of particles are altered in direction by the imposed outer field as they travel from one cluster to an immediately adjacent cluster.

33. The method of claim 32, wherein at least some of the plurality of particles have no added out-field change in direction as they travel from one cluster to an immediately adjacent cluster.

34. The method of claim 27, wherein at least one of the plurality of deterministic light gradients comprises a light trap.