Claims:
1. A 3D imaging system for biological cells, comprising:
a first microfluidic channel comprising an inlet and an outlet, the inlet adapted to receive a fluidic media containing cells into the first microfluidic channel, and the outlet adapted to dispense the fluidic media from the first microfluidic channel; and
a second microfluidic channel comprising a first air inlet and a second opposite air inlet; wherein the second microfluidic channel orthogonally intersects the first microfluidic channel forming an intersection region in the first microfluidic channel; wherein each of the first and second air inlets is adapted to receive pressurized air that flows towards the intersection region, and wherein the air flow creates, at the intersection region, two opposite air-liquid interfaces which act to create a virtual channel width for the cells moving along the first microfluidic channel;
wherein upper side and lower side of the first microfluidic channel, at least in the intersection region, are made of different materials such that the air-liquid interface of the fluidic media has different contact angles with bottom surface and top surface of the first microfluidic channel; and
wherein difference in the contact angle of the fluidic media at the two opposing surfaces distorts the air-liquid interfaces to a non-symmetrical catenary curve to result in variation in cross section along height of the first channel for flow of the fluidic media such that the variation generates variation in flow velocity across the first microfluidic channel height causing the cells to rotate to enable capturing images of a rotating cell in different orientations.
2. The 3D imaging system as claimed in claim 1, wherein the two different materials for the upper side and the lower side of the first microfluidic channel are polydimethylsiloxane and glass, and wherein the fluidic media is Phosphate-buffered Saline.
3. The 3D imaging system as claimed in claim 2, wherein the first microfluidic channel and the second microfluidic channel are fabricated on polydimethylsiloxane bonded to a glass substrate, and wherein the fabrication is done using soft lithography.
4. The 3D imaging system as claimed in claim 1, wherein the system comprises a high speed camera to capture a plurality of images of the rotating cell from different angles.
5. The 3D imaging system as claimed in claim 4, wherein the system includes a processor to process the plurality of captured images to map cell and nucleus boundaries and to reconstruct 3D image of the cell.
6. The 3D imaging system as claimed in claim 5, wherein the processor is used to calculate volume, surface area and ellipticity of the cell and its nucleus.
7. The 3D imaging system as claimed in claim 1, wherein the system comprises a pressure control device to control pressure of air supplied through the first air inlet and the second air inlet to achieve different virtual channel widths to allow for 3D imaging of cells of different sizes.
8. A method for preparing 3D images of biological cells, comprising the steps of:
(a) providing a microfluidic system comprising:
a first microfluidic channel for flow of a fluidic media containing cells, wherein upper side and lower side of the first microfluidic channel are made of different materials such that an air-liquid interface of the fluidic media has different contact angles with bottom surface and top surface of the first microfluidic channel; and
a second microfluidic channel that orthogonally intersects the first microfluidic channel forming an intersection region in the first microfluidic channel; the second microfluidic channel adapted to receive pressurized air at two opposite ends;
(b) letting a fluidic media containing cells pass through the first microfluidic channel so as to produce a flow;
(c) flowing pressurized air into the second microfluidic channel through the two opposite ends, wherein the pressurized air flows towards the intersection region to create, at the intersection region, two opposite air-liquid interfaces which act to create a virtual channel width for the cells moving along the first microfluidic channel; wherein difference in the contact angle of the air-liquid interfaces at the two opposing surfaces of the first channel distorts the air-liquid interfaces to a non-symmetrical catenary curve to result in variation in cross section along height of the channel for flow of the fluidic media such that the variation generates variation in flow velocity across the first microfluidic channel height;
(d) letting the cells rotate under influence of the variation in flow velocity across the first microfluidic channel height, as movement of the cells through the intersection region is controlled; and
(d) obtaining a plurality of images of a rotating cell in different orientations as it rotates while moving through the intersection region.
9. The method as claimed in claim 8, comprising the step of controlling pressure of air supplied through the two opposite ends of the second air microfluidic channel to vary the air-liquid interface such that the resultant virtual channel width, at the intersection region, allows capturing a plurality of images of a rotating cell depending on size of the cell.
10. The method as claimed in claim 8, comprising the step of processing the plurality of images to reconstruct 3D images of the cells.
, Description:
FIELD OF THE INVENTION
[0001] The present disclosure pertains to technical field of microfluidic devices. In particular, the present disclosure pertains to air-liquid or liquid-liquid interfaces based microfluidic system for 3D imaging of a biological system such as a single cell.

BACKGROUND OF THE INVENTION
[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
[0003] 3D imaging of live cells helps in identifying biophysical properties of cellular and intracellular components of a biological cell. Confocal microscopy has been widely used for 3D imaging of live cells. Alternates for confocal microscopy include stimulated Raman scattering microscopy [“Label-Free Biomedical Imaging with High Sensitivity by Stimulated Raman Scattering Microscopy,” C. W. Freudiger et al., Science (80-. )., vol. 322, no. 5909, pp. 1857–1861, Dec. 2008], harmonic generation microscopy [“Label-free 3D visualization of cellular and tissue structures in intact muscle with second and third harmonic generation microscopy,” M. Rehberg, F. Krombach, U. Pohl, and S. Dietzel, PLoS One, vol. 6, no. 11, p. e28237, Nov. 2011], quantitative phase imaging [“Three-dimensional label-free imaging and quantification of lipid droplets in live hepatocytes,” K. Kim, S. Lee, J. Yoon, J. Heo, C. Choi, and Y. Park, Sci. Rep., vol. 6, no. 1, p. 36815, Dec. 2016.], optical diffraction tomography [“Three-dimensional label-free imaging and analysis of Pinus pollen grains using optical diffraction tomography,” G. Kim, S. Lee, S. Shin, and Y. Park, Sci. Rep., vol. 8, no. 1, p. 1782, Dec. 2018] etc.
[0004] Among the engineered microfluidic channel-based approaches Y. Li et al. [“Accurate label-free 3-part leukocyte recognition with single cell lens-free imaging flow cytometry,” Comput. Biol. Med., vol. 96, no. March, pp. 147–156, May 2018.] and V. K. Jagannadh, M. D. Mackenzie, P. Pal, A. K. Kar, and S. S. Gorthi [“Slanted channel microfluidic chip for 3D fluorescence imaging of cells in flow,” Opt. Express, vol. 24, no. 19, p. 22144, Sep. 2016] use fluorescent dyes to image the nucleus. Huang et al. [“3D cell electrorotation and imaging for measuring multiple cellular biophysical properties,” Lab Chip, vol. 18, no. 16, pp. 2359–2368, 2018] used electrorotation to study the morphology of HeLa and B-Lymphocytes.
[0005] Therefore, most of the aforementioned prior art techniques possess drawbacks and limitations which limit their cost effectiveness and/or flexibility. For example, they rely on use of fluorescent dyes for cellular and intracellular imaging of live cells. Secondly, instruments like confocal imaging, optical tomography required in implementing these techniques, are expensive. Besides there is requirement of a device for 3D imaging of live cells that takes care of variation is size of the cells.
[0006] There is, therefore, need for an alternate approach for 3 D imaging of live cells that overcomes above limitations. The present invention satisfies the above need, as well as others, and generally overcomes the deficiencies found in the prior art.
[0007] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.
[0008] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability.

OBJECTS OF THE INVENTION
[0009] It is an object of the present disclosure to provide a new and improved 3D imaging system for imaging of live cells that overcomes one or more disadvantages associated with previously known devices and techniques for 3D imaging of live cells.
[0010] It is an object of the present disclosure to provide a 3D imaging system for live cells that is based on a microfluidic chip and a high-speed camera for 3D reconstruction of the cell and nucleus for a cost-effective 3D imaging of live cells.
[0011] It is a further object of the present disclosure to provide a new and improved microfluidic system for rotation of live cells so that images of the cell may be obtained from different orientations of the cells.
[0012] It is a further object of the present disclosure to provide a 3D imaging system for live cells that is label-free.
[0013] It is another object of the present disclosure to provide a 3D imaging system for live cells that can accommodate difference in cell sizes.
[0014] It is another object of the present disclosure to provide a microfluidic chip for on-chip rotation of live cells.
[0015] It is another object of the present disclosure to provide a microfluidic chip based 3D imaging system for live cells that can be used for different cells with comparable sizes, thereby offering flexibility and scalability.
[0016] It is another object of the present disclosure to provide a microfluidic chip based 3D imaging system for live cells that solves the channel clogging problem inherent in conventional bio-microfluidic devices.
[0017] It is another object of the present disclosure to provide a microfluidic chip based 3D imaging system for live cells that allows dynamic adjustment of microfluidic channel width to achieve desirable channel width meeting the requirement of cells of different sizes.
[0018] It is another object of the present disclosure to provide a microfluidic chip based label-free 3D imaging system of intracellular components like nucleus.
[0019] It is yet another object of the present disclosure to provide a quick, cost-effective and scalable method for 3D imaging of a biological system such as single cell.

SUMMARY
[0020] Aspects of the present disclosure relate to a new and improved microfluidic system based imaging system for 3D imaging of a biological system such as single cell. The microfluidic system disclosed herein can enable 3D imaging by rotating individual cells, and can solve the channel clogging problem inherent in conventional bio-microfluidic devices. Further, the disclosed system enables capturing of a plurality of images of a cell from different angles/orientations and reconstruction of 3D image.
[0021] In an aspect, the proposed 3D imaging system includes a first microfluidic channel second microfluidic channel that orthogonally intersects the first microfluidic channel to form an intersection region in the first microfluidic channel. The first microfluidic channel has an inlet to receive a fluid that contains cells (hereinafter referred to as fluidic media), and an outlet to dispense the fluidic media from the first microfluidic channel, so that the cells containing media can flow through the first microfluidic channel.
[0022] In an aspect, the second microfluidic channel has a first air inlet and a second opposite air inlet located at two opposite ends on the two sides of the intersection region. Each of the first air inlet and the second air inlet is adapted to receive pressurized air that flows towards intersection region of the first channel. The flow of the pressurized air, on interaction with the fluidic media flowing through the first microfluidic channel, creates, at the intersection region, two opposite air-liquid interfaces, which act to create a virtual channel, defined by a virtual channel width, for the cells moving along the first microfluidic channel.
[0023] In an aspect, the first microfluidic channel, at least in the intersection region, has upper side and lower side made of different materials such that air-liquid interface of the fluidic media has different contact angles with bottom surface and top surface of the first microfluidic channel. The difference in the contact angle of the fluidic media at the two opposing surfaces distorts the air-liquid interfaces to a non-symmetrical catenary curve to result in variation in the virtual channel width along height of the first channel for flow of the fluidic media. In an aspect, the variation in cross section generates variation in flow velocity across height of the first microfluidic channel, which causes the cells to rotate due to hydrodynamic forces, as they move through the virtual channel.
[0024] In an aspect, rotation of the cell enables capturing of images of the cell from different angles/orientations.
[0025] In an aspect, the two different materials for the upper side and the lower side of the first microfluidic channel can be polydimethylsiloxane (PDMS) and glass.
[0026] In an aspect, the fluidic media used can be Phosphate-buffered Saline (PBS) or any fluid, which exhibits different contact angles with polydimethylsiloxane and glass.
[0027] In an aspect, the first microfluidic channel and the second microfluidic channel can be fabricated on polydimethylsiloxane bonded to a glass substrate, and the fabrication is can be done using soft lithography.
[0028] In an aspect, the virtual channel created by the air-liquid interfaces at the intersection region of the first channel, and having width less than width of the first microfluidic channel, also acts as a constriction to control movement of cells through the intersection region. The virtual channel width can be controlled by varying pressure of air applied at the first air inlet and the second air inlet. In an aspect, controlling movement of cells through the intersection region allows to capture a plurality of images of the rotating cell from different angles.
[0029] In an aspect, the pressure of air applied at the first air inlet and the second air inlet can be controlled by a pressure control device, which also allows for 3D imaging of cells of different sizes by varying the width of the virtual channel.
[0030] In an aspect, the system can comprise a high speed camera to capture a plurality of images of the rotating cell from different angles.
[0031] In an aspect, the system can include a processor to process the plurality of captured images to map cell and nucleus boundaries and to reconstruct 3D image of the cell.
[0032] In an aspect, the processor can be used to calculate volume, surface area and ellipticity of the cell and its nucleus.
[0033] An aspect of the present disclosure relates to a method for 3D imaging of biological cells using the disclosed system.
[0034] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS
[0035] The accompanying drawings are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.
[0036] FIG. 1 illustrates a schematic view of a microfluidic system of the proposed system for 3D imaging of biological cells, showing rotation of a cell as it passes through a constriction formed by air liquid interfaces, in accordance with one embodiment of the present disclosure.
[0037] FIG. 2 schematically shows a sectional view of the first microfluidic channel with the air-liquid interfaces forming catenary curves owing to difference in contact angles of air-liquid interface of the fluidic media with top surface and bottom surface, resulting in variation in width of the virtual channel across height of the channel, in accordance with embodiments of the present disclosure.
[0038] FIG. 3 shows time-lapse images of a single cell rotating at the air-liquid interfaces with the cellular and nucleus boundary superimposed on the recoded images, in accordance with embodiments of the present disclosure.
[0039] FIG. 4 shows reconstructed 3D images of cell surface and nucleus surface from point cloud using alpha shape function in MATLAB, in accordance with embodiments of the present disclosure.
[0040] FIGs. 5A and 5B shows calculated volume and surface area of three cells and nucleus of FIG. 4, in accordance with embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION
[0041] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure as defined by the appended claims.
[0042] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.
[0043] Unless the context requires otherwise, throughout the specification which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense that is as “including, but not limited to.”
[0044] 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. Thus, the 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. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0045] As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
[0046] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein.
[0047] All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. “such as”) provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.
[0048] The headings and abstract of the invention provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.
[0049] Various terms as used herein. To the extent a term used in a claim is not defined herein, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.
[0050] Reference will now be made in detail to the exemplary embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.
[0051] Embodiments of the present disclosure provide a technique for 3D imaging of living biological cells. Specifically, embodiments of the present disclosure use a microfluidic system, a high-speed camera, a pressure control device and a controller to capture a plurality of images of the cells from different angles as the cell rotates, and thereafter reconstruct 3D images of the cells.
[0052] In an embodiment, the microfluidic system includes a first microfluidic channel (also referred to as first micro-channel and the two terms used interchangeably hereinafter) adapted for flow of a fluidic media containing the cells, and a second microfluidic channel (also referred to as second micro-channel and the two terms used interchangeably hereinafter) that orthogonally intersects the first microfluidic channel to create an intersection region. The second microfluidic channel is adapted to receive pressurized air from two opposite ends that flows towards the intersection region. The pressurized air creates, in the intersection region, two opposing air-liquid interfaces creating a virtual constriction (also referred to as virtual channel), having a virtual channel width, in the first microfluidic channel for the fluidic media to flow through.
[0053] In an embodiment, the first microfluidic channel is made such that its top side and the bottom side, at least in the intersection region, are made of different materials such that the air-liquid interface of the fluidic media has different contact angles with bottom surface and top surface of the first microfluidic channel. The difference in the contact angles at the two opposing surfaces distorts the air-liquid interfaces to a non-symmetrical catenary curve. The opposing deformed air-liquid interfaces make the virtual channel narrower at one side and broader on the opposite side, i.e. having variation in width along height of the channel. The resultant variation in cross sectional area for flow of the fluidic media generates variation in flow velocity across the height, causing the cells to rotate about a horizontal axis due to resultant hydrodynamic forces.
[0054] In an embodiment, the upper side of the first microfluidic channel can be made of polydimethylsiloxane and the bottom side can be of glass. Specifically, the microfluidic system can be fabricated on polydimethylsiloxane bonded to a glass substrate, and the fabrication can be done using soft lithography.
[0055] In an embodiment, the high speed camera is used to capture a plurality of images of the rotating cell from different angles, and the processor is used to process the plurality of captured images to map cell and nucleus boundaries and to reconstruct 3D image of the cell. The processor can also be used to calculate volume, surface area and ellipticity of the cell and its nucleus.
[0056] In an embodiment, the virtual channel width can be controlled using the pressure control device by controlling pressure of air supplied to two end of the second microfluidic channel. In an embodiment, the virtual channel width can be maintained to make the cells move at desired linear speed so that adequate images of the rotating cells at different angles may be captured. Thus, the pressure control device also enables use of the microfluidic system for cells of different sizes.
[0057] FIG. 1 illustrates an exemplary configuration of one embodiment of the 3D imaging system, i.e. the microfluidic system 100, for live biological cells. The microfluidic system 100 can consist of a plus-shaped channel-network fabricated on a glass substrate backed polydimethylsiloxane (PDMS) using soft lithography. The microfluidic system 100 can include a first microfluidic channel/ first micro-channel 102, a second microfluidic channel/ second micro-channel 108, and an intersection region 112. As shown in FIG. 1, the first and second microfluidic channels can intersect perpendicularly to each other to form the intersection region 112. The first microfluidic channel 102 can include an inlet 104 through which a fluidic media containing cells can be introduced for flow through the first channel 102. The opposing outlet end 106 can be used to dispense of the fluidic media flowing out of the first microfluidic channel 102. Cells, such as cell 114, which comprises a nucleus 114a and an outer boundary 114b, suspended in a buffer or solution can be caused to flow from the inlet end 104 to the outlet end 106, and a flow speed of the buffer or solution (also referred to as fluidic media) can be adjusted as required. The second microfluidic channel 108 can include a first air inlet 110-a and a second opposite air inlet 110-b through which a pressurized gas (e.g. air) can be introduced into the second microfluidic channel 108.
[0058] As shown in FIG. 2, when air pressure is applied from the air inlets 110-a and 110-b toward the intersection region 112, the air creates two opposing air-liquid interfaces, such as 116-1 and 116-2 (collectively referred to as 116) at the intersection region 112. The air-liquid interfaces 116 create a virtual constriction in the intersection region, which can be sized to control flow of the cells through the interface region 112. The constriction can be sized such that a single cell passing through the constriction moves at a desired speed.
[0059] In an embodiment, a pressure control device can be used to control the pressure of air supplied through the inlets 110-a and 110-b in order to achieve different virtual channel widths.
[0060] In an aspect, the microfluidic system 100 can be made such that its top side and bottom side are made of different materials such that air-liquid interface of the fluidic media in the first microfluidic channel has different contact angles with bottom surface and top surface of the first microfluidic channel 102. For example, as shown in the exemplary illustrations of FIG. 2, the upper side 118 of the microfluidic channels can be made of polydimethylsiloxane (PDMS) and the bottom side 120 can be made of glass. Specifically, the microfluidic system can be fabricated on polydimethylsiloxane bonded to a glass substrate, and the fabrication can be done using soft lithography.
[0061] As shown in cross sectional view in FIG. 2, the contact angle of the air-liquid interface 116 with the top surface, which is made of PDMS, is larger compared to contact angle of the air-liquid interface 116 with the bottom surface made of glass. The difference in contact angles at the two opposing surfaces distorts the air-liquid interfaces 116 to a non-symmetrical catenary curve, i.e. upper half of the air-liquid interface curve is not symmetric to the lower half. As would be evident to those skilled in the art, the two halves would be symmetric to each other if the contact angles with the top surface and the bottom surface were same. The opposing deformed air-liquid interfaces, 116-1 and 116-2, make the channel narrower, as shown by W2, on the top side, and broader, as shown by W1, on the opposite lower side. Thus, the resultant channel has variation in cross section along height of the channel. The variation in cross sectional area for flow of the fluidic media generates variation in flow velocity across the height causing the cells to rotate due to resultant hydrodynamic forces, as the cells pass through the created virtual channel.
[0062] In an aspect, Phosphate-buffered Saline (PBS), which exhibits different contact angles with PDMS and glass, can be used as fluidic media for flow of cells through the first channel 102.
[0063] In an aspect, a high speed camera can be used to capture a plurality of images of the rotating cell from different angles. In an application, a camera having capability to capture 2000 frames per second was used and images at different angles of rotation captured by flowing cells from one side at extremely low flow rates.
[0064] In an aspect, a processor can be used to process the plurality of captured images to map cell and nucleus boundaries and to reconstruct 3D image of the cell. Custom image processing algorithms developed in MATLAB, can be used for boundary identification and shape reconstruction. The processor can also be used to calculate volume, surface area and ellipticity of the cell and its nucleus.
[0065] In exemplary testing, peripheral blood mononuclear cells were extracted from a whole blood sample and suspended in PBS (1:100). The sample was made to flow in the first microfluidic channel and two air-liquid interfaces were created in the orthogonally located second microfluidic channel designed to obstruct the cell. A high-speed camera captures the images of a rotating cell at 2000 fps. Image reconstruction was performed in MATLAB to extract the cell and the nucleus boundary. The extracted contours superimposed on recorded images is shown in FIG. 3. These contours were rotated in 3D to generate the point cloud for a single cell. The 3D plot of the cell surface and nucleus surface using alpha shape function is shown in FIG. 4. It can be observed that the ellipticity in nucleus shape has been captured in the 3D model. The cell and nucleus volume and surface area are calculated for three cells as shown in FIG. 5A-5B.
[0066] In another aspect, the present disclosure provides a method for preparing 3D images of biological cells, wherein the method can include a step of providing a microfluidic system. The microfluidic system having a first microfluidic channel for flow of a fluidic media containing cells. Upper side and lower side of the first microfluidic channel are made of different materials such that the air-liquid interface of the fluidic media has different contact angles with bottom surface and top surface of the first microfluidic channel. The microfluidic system having a second microfluidic channel that orthogonally intersects the first microfluidic channel forming an intersection region in the first microfluidic channel; wherein the second microfluidic channel is adapted to receive pressurized air at two opposite ends.
[0067] In an aspect, the proposed method further includes step of letting a fluidic media containing cells pass through the first microfluidic channel so as to produce a flow.
[0068] In an aspect, the proposed method further includes step of flowing pressurized air into the second microfluidic channel through the two opposite ends. The pressurized air flows towards the intersection region, and create, at the intersection region, two opposite air-liquid interfaces which act to create a virtual channel width for the cells moving along the first microfluidic channel. Difference in the contact angle of the fluidic media at the two opposing surfaces of the first channel distorts the air-liquid interfaces to a non-symmetrical catenary curve, which results in variation in cross section along height of the channel for flow of the fluidic media, and the variation in cross section along height generates variation in flow velocity across the first microfluidic channel height.
[0069] In an aspect, the proposed method further includes steps of letting the cells rotate under influence of the variation in flow velocity across the first microfluidic channel height, as movement of the cells through the intersection region is controlled; and obtaining a plurality of images of the cells as they rotate while moving through the intersection region.
[0070] In an aspect, the method may also comprise the step of controlling, using a pressure control device, pressure of air supplied through the two opposite ends of the second microfluidic channel to vary the air-liquid interface such that the resultant virtual channel width, at the intersection region, allows capturing a plurality of images of a rotating cell depending on size of the cell.
[0071] In an aspect, the method may also comprise the step of processing, using a processor, the plurality of images to reconstruct 3D images of the cells.
[0072] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the appended claims.

ADVANTAGES OF THE PRESENT INVENTION
[0073] The present disclosure provides a new and improved 3D imaging system for imaging of live cells that overcomes one or more disadvantages associated with previously known devices and techniques for 3D imaging of live cells.
[0074] The present disclosure provides a 3D imaging system for live cells that is based on a microfluidic chip and a high-speed camera for 3D reconstruction of the cell and nucleus for a cost effective 3D imaging of live cells.
[0075] The present disclosure provides a new and improved microfluidic system for rotation of live cells so that images of the cell may be obtained from different angles.
[0076] It is a further object of the present disclosure to provide a 3D imaging system for live cells that is label-free.
[0077] The present disclosure provides a 3D imaging system for live cells that can accommodate difference in cell sizes.
[0078] The present disclosure provides a microfluidic chip based 3D imaging system for live cells that can be used for different cells with comparable sizes, thereby offering flexibility and scalability.
[0079] The present disclosure provides a microfluidic chip based 3D imaging system for live cells that solves the channel clogging problem inherent in conventional bio-microfluidic devices.
[0080] The present disclosure provides a microfluidic chip based 3D imaging system for live cells that allows dynamic adjustment of microfluidic channel width to achieve desirable channel width.
[0081] The present disclosure provides a microfluidic chip based 3D imaging system for live cells that enables real time adjustment of microfluidic channel dimension.
[0082] The present disclosure provides a quick, cost effective and scalable method for 3D imaging of a biological system such as single cell.