WO2017054839A1

WO2017054839A1 - A technique for aligning a non-spherical biological entity in a flow cell

Info

Publication number: WO2017054839A1
Application number: PCT/EP2015/072273
Authority: WO
Inventors: Oliver Hayden; Lukas RICHTER; Matthias UGELE
Original assignee: Siemens Healthcare Gmbh
Priority date: 2015-09-28
Filing date: 2015-09-28
Publication date: 2017-04-06

Abstract

A technique is presented for aligning, in a desired region within a flow chamber of a flow cell, a non-spherical biological entity carried in a sample. The flow chamber has a rectangular cross-section. A bottom flow input module, a top flow input module and a sample input module provide a first fluid, a second fluid, and the sample, respectively, to the flow chamber. The first and the second fluids laminarly flow along a bottom and a top wall of the flow chamber and the sample laminarly flows sandwiched between them. By controlling rate of flow of the first and/or the second fluid the sample flow, and thus the non-spherical biological entity, is focused in the desired region. An acoustic transducer generates a standing acoustic wave having pressure node linearly arranged along an axis passing through the desired region to orient the non-spherical biological entity in the desired region.

Description

A technique for aligning a non-spherical biological entity in a flow cell

The present invention relates to techniques for aligning a non-spherical biological entity flowing in a sample that is to be inspected by an imaging device. Medical technology in recent times has witnessed advent of numerous medical devices and microscopy techniques. A lot of these microscopy techniques are used for imaging microscopic specimens or samples for analyzing one or more characteris^¬ tics of the sample, or more precisely for determining one or more characteristics of a component, for example red blood cell (RBC), in the sample, for example blood sample. Examples of characteristics of the component, say RBC, that may be de^¬ termined may include a volumetric measurement of the RBC, a morphological study of the RBC, and so on and so forth. In general for any imaging dependant analysis, an ^xin-focus' im^¬ age or output from the imaging device is essential for carry^¬ ing out specific and detailed analysis of the component of the sample. Furthermore, when the component of the sample is non-spherical entity an orientation of the non-spherical en- tity with respect to the imaging device, i.e. with respect to an imaging direction, is also essential, for example image of the RBC standing on its side is an undesired orientation as in such orientation only sides of RBC are visible. However, with respect to the imaging direction, an image of the RBC oriented such that a full face or one side of the disc shape is visible is a desired orientation as in such orientation images will reveal lot more information which is essential for volumetric or morphological study of the RBC. For example, a non-spherical biological entity, hereinafter also referred to as the entity, carried in a sample may be studied or inspected by detecting and analyzing interference patterns formed in interferometric microscopy, for example digital holographic microscopy (DHM) . However, throughput of DHM device or any other imaging device, i.e. rate of number of images or interference patterns provided by the device, is highly dependent on providing the sample to a field of view, hereinafter the FOV, of the imaging device, as the sample should be provided with in depth of field at a focus of the device to obtain ^xin-focus' or sharp images or interference patterns as output of the imaging device. Providing the enti^¬ ty in the sample as flowing in a flow cell, for example simi- lar to the way sample is provided in flow cytometry, is an efficient way of providing the sample to the imaging device. It has several advantages for example it is easier to main^¬ tain the entity of the sample, for example RBCs in the blood, in their native morphology in a fluid flow as compared to placing the entity on a slide. Furthermore, by providing the sample in a flow, the sample, and thus the entities in the sample, may be provided continuously for a time period of im^¬ aging and thus a larger amount of sample, i.e. larger number of the entities, may be imaged which is beneficial for sta- tistical means as compared to scanning or imaging a smaller amount of the sample.

However, providing the sample as flowing in a flow cell has also certain disadvantages. One disadvantage is focusing of the sample in the flow cell. The entities in the sample for example RBCs in a diluted or whole blood sample flowing through the flow cell migrate to different sections of the flow cell and are not arranged in a desired region of the flow cell. Some of the entities while flowing in the flow cell migrate to the walls of the flow cell and contact be^¬ tween the entities with the wall results into surface adhe^¬ sion of the entities on the flow cell walls, or entities start disintegrating to form debris. Furthermore, since the entities flow to different sections of the flow cell, some of the entities of the sample in the flow cell may be either completely out of the FOV or may be in the FOV but out of fo^¬ cus. The entities of the sample that are completely out of the FOV are not represented in the image of the interference pattern. The entities of the sample that are in the FOV but not in focus are imaged but parts or segments of the image or the interference pattern that represent such entities lack sharpness i.e. are out of focus or to say that the sharpness of segments of the interference pattern or the image repre^¬ senting such entities are either low or not of acceptable quality or blurred.

Such entities flowing as part of the sample in the flow cell or flow channel may be brought in focus by readjusting the focus of the interferometric microscopic device or the imag^¬ ing device but the entities of the flowing samples are dynam^¬ ic so there is no time to adjust the focus of the imaging de^¬ vice. Another approach may be to provide the sample in such a way in the flow cell that the sample flows within a desired region of the flow cell, and then the imaging device can be statically focused at the desired region with the depth of field of the imaging device aligned with the desired region and subsequently in-focus imaging of the entities of the sam- pie may be achieved. However, it is a challenge to control the flow of sample in such flow cells, more particularly to control the entities of the sample in the flow cell, so that the samples, or the entities of the sample, are positioned or focused in a desired region of the flow cell. Furthermore, the non-spherical biological entities are also required to be oriented in a desired orientation in the desired region.

Thus, the need is to focus and to orient one or more entities in the desired region, in short there is a need of aligning the non-spherical biological entity in the desired region.

Thus the object of the present disclosure is to provide a technique for aligning a non-spherical biological entity car^¬ ried in a sample into a desired region in a flow cell. The above object is achieved by a flow cell for aligning a non-spherical biological entity carried in a sample into a desired region in the flow cell according to claim 1, a method for aligning a non-spherical biological entity carried in a sample into a desired region in a flow cell according to claim 8, and a system for aligning a non-spherical biological entity carried in a sample into a desired region according to claim 13. Advantageous embodiments of the present technique are provided in dependent claims.

A first aspect of the present technique presents a flow cell for aligning a non-spherical biological entity carried in a sample into a desired region in the flow cell. The aligning of the non-spherical biological entity in the desired region is achieved by focusing and orienting the non-spherical bio^¬ logical entity in the desired region. The non-spherical bio^¬ logical entity is to be inspected by an imaging device. The flow cell includes a flow chamber, a bottom flow input mod- ule, a top flow input module, a sample input module and an acoustic transducer. The flow chamber has a rectangular cross-section, a top wall, a bottom wall opposite to the top wall, a first side wall, a second side wall opposite to the first side wall and the desired region. The rectangular cross-section includes a square cross-section.

The bottom flow input module receives a first fluid and pro^¬ vides the first fluid to the flow chamber such that the first fluid laminarly flows in the flow chamber in form of a bottom laminar flow along the bottom wall from one end of the flow chamber towards another end of the flow chamber. The bottom flow input module controls a rate of flow of the first fluid in the flow chamber. The top flow input module receives a se^¬ cond fluid and provides the second fluid to the flow chamber such that the second fluid laminarly flows in the flow cham^¬ ber in form of a top laminar flow along the top wall from one end of the flow chamber towards another end of the flow chamber. The top flow input module controls a rate of flow of the second fluid in the flow chamber.

The sample input module receives the sample and provides the sample to the flow chamber such that the sample laminarly flows in the flow chamber in form of a sample laminar flow from one end of the flow chamber towards another end of the flow chamber. The sample laminar flow is sandwiched between the top laminar flow and the bottom laminar flow. The acoustic transducer generates a standing acoustic wave having a pressure node linearly arranged along an axis passing through the desired region. The standing acoustic wave may be one di^¬ mensional or two dimensional. When the standing acoustic wave is two dimensional, the acoustic force acting along a first direction will be different, i.e. stronger or weaker, com- pared to the acoustic force acting along a second direction.

Hereinafter, the ^xrate of flow' has also been referred to as the flow rate. In the flow cell, by defining or by increasing or by decreasing the flow rate of the first fluid, a height of the bottom laminar flow is controlled or varied. Similarly, by defining or by increasing or by decreasing the flow rate of the second fluid, a height of the top laminar flow is controlled or varied. In the present technique, ^xwidth' or ^xheight' have been in^¬ terchangeably used for any laminar flow, not including the sample laminar flow, and mean an extension of that laminar flow along the rectangular cross-section of the flow chamber from a wall of the flow chamber along which the laminar flow is aligned towards the opposite wall, for example ^xwidth' or ^xheight' of the bottom laminar flow means an extension of the bottom laminar flow along the rectangular cross-section of the flow chamber from the bottom wall of the flow chamber towards the top wall of the flow chamber. Similarly ^xwidth' or ^xheight' of the top laminar flow means an extension of the top laminar flow along the rectangular cross-section of the flow chamber from the top wall of the flow chamber towards the bottom wall of the flow chamber. For the sample laminar flow, width means an extension of the sample laminar flow along the rectangular cross-section of the flow chamber between the first and the second side walls. For the sample laminar flow, height means an extension of the sample laminar flow along the rectangular cross-section of the flow chamber between the top and the bottom walls. For the sample laminar flow, ^xlateral position' means a location of a cross-section of the sample laminar flow along the rec- tangular cross-section of the flow chamber between the first and the second side walls, and ^λ longitudinal position' means a location of the cross-section of the sample laminar flow along the rectangular cross-section of the flow chamber between the top and the bottom walls.

In the flow cell, by controlling or varying the height of the bottom laminar flow and/or the top laminar flow, the width and/or the height and/or the longitudinal position of the sample laminar flow is controlled or varied. By defining the width and/or the height and/or the longitudinal position of the sample laminar flow, the sample laminar flow is focused i.e. moved into or positioned into the desired region of the flow cell by moving the sample laminar flow between the desired region and the top and/or the bottom walls. Since the non-spherical biological entities are carried in the sample or more particularly in the sample laminar flow, the focusing of the sample laminar flow in the desired region results into focusing of the non-spherical biological entity or entities in the desired region. Furthermore, a differential pressure is formed by the standing acoustic wave at different parts of the flow chamber and especially towards the pressure node and this differential pressure acts on the non-spherical biologi^¬ cal entity to orient the non-spherical biological entity car^¬ ried in the sample into the desired region.

In an embodiment of the flow cell, the flow cell includes a first side flow input module. The first side flow input mod^¬ ule receives a first side fluid and provides the first side fluid to the flow chamber such that the first side fluid laminarly flows in the flow chamber in form of a first side laminar flow moving from the one end of the flow chamber towards the another end of the flow chamber. The first side laminar flow is sandwiched between the top laminar flow and the bottom laminar flow and between the first side wall and the sample laminar flow. The first side flow input module controls a rate of flow of the first side fluid in the flow chamber .

The ^xwidth' of the first side laminar flow means an extension of the first side laminar flow along the rectangular cross- section of the flow chamber from the first side wall of the flow chamber towards the second side wall of the flow cham- ber. In the flow cell, by controlling or varying the width of the first side laminar flow, the width and/or the height and/or the lateral position of the sample laminar flow is controlled or varied in the flow chamber i.e. by moving the sample laminar flow between the desired region and the first side wall. By defining the width and/or the height and/or the lateral position of the sample laminar flow, the sample lami^¬ nar flow is focused i.e. one or more of the non-spherical bi^¬ ological entity is moved into or positioned into the desired region of the flow cell.

In another embodiment of the flow cell, the flow cell in^¬ cludes a second side flow input module. The second side flow input module receives a second side fluid and provides the second side fluid to the flow chamber such that the second side fluid laminarly flows in the flow chamber in form of a second side laminar flow moving from the one end of the flow chamber towards the another end of the flow chamber. The second side laminar flow is sandwiched between the top laminar flow and the bottom laminar flow and between the second side wall and the sample laminar flow. The second side flow input module controls a rate of flow of the second side fluid in the flow chamber.

The ^xwidth' of the second side laminar flow means an exten- sion of the second side laminar flow along the rectangular cross-section of the flow chamber from the second side wall of the flow chamber towards the first side wall of the flow chamber. In the flow cell, by controlling or varying the width of the second side laminar flow, the width and/or the height and/or the lateral position of the sample laminar flow is controlled or varied in the flow chamber i.e. by moving the sample laminar flow between the desired region and the second side wall. By defining the width and/or the height and/or the lateral position of the sample laminar flow, the sample laminar flow is focused i.e. one or more of the non- spherical biological entity is moved into or positioned into the desired region of the flow cell.

The first and the second side fluids may be provided either simultaneously or sequentially in any order.

In another embodiment of the flow cell, the sample input mod- ule controls a rate of flow of the sample in the flow cham^¬ ber. Thus amount of sample forming the sample laminar flow is controlled, which in turn contributes to the width and/or the height of the sample laminar flow. In another embodiment of the flow cell, the flow chamber is a microfluidic channel. Thus the flow cell is compact.

In another embodiment of the flow cell, the acoustic trans^¬ ducer is an ultrasonic transducer and wherein the standing acoustic wave is a standing ultrasonic wave. This provides a simple way of implementing the present technique.

In another embodiment of the flow cell, the ultrasonic trans^¬ ducer is a piezoelectric ceramic. The piezoelectric ceramic provides a simple way of implementing the present technique.

A second aspect of the present technique presents a method for aligning a non-spherical biological entity carried in a sample into a desired region in a flow cell. The non- spherical biological entity is to be inspected by an imaging device having a depth of field in a field of view of the im^¬ aging device. The flow cell includes a flow chamber having a rectangular cross-section, a top wall, a bottom wall opposite to the top wall, a first side wall, a second side wall oppo^¬ site to the first side wall and the desired region. In the method, a first fluid is provided to the flow chamber such that the first fluid laminarly flows in the flow chamber in form of a bottom laminar flow along the bottom wall from one end of the flow chamber towards another end of the flow chamber. Simultaneously along with or subsequent to the above mentioned step, in the method, a second fluid is provided to the flow chamber such that the second fluid laminarly flows in the flow chamber in form of a top laminar flow along the top wall from the one end of the flow chamber towards the an^¬ other end of the flow chamber.

Simultaneously along with or subsequent to the above men- tioned step, in the method, the sample is provided to the flow chamber such that the sample along with the one or more non-spherical biological entity laminarly flows in the flow chamber in form of a sample laminar flow from the one end of the flow chamber towards the another end of the flow chamber and wherein the sample laminar flow is sandwiched between the top laminar flow and the bottom laminar flow.

In the method, a rate of flow of the first fluid and/or a rate of flow of the second fluid in the flow chamber is con- trolled in order to achieve focusing of the sample carrying the non-spherical biological entity into the desired region. Furthermore, the desired region is aligned with the depth of field in the field of view of the imaging device. In the method, a standing acoustic wave having a pressure node is generated such that the pressure node of the standing acous^¬ tic wave is linearly arranged along an axis that passes through the desired region, The differential pressure formed by the standing acoustic wave at different parts of the flow chamber and specially towards the pressure node acts on the non-spherical biological entity to orient the non-spherical biological entity carried in the sample into the desired re^¬ gion . In the method, by defining or by increasing or by decreasing the flow rate of the first fluid, the height of the bottom laminar flow in the flow cell is controlled or varied. Simi^¬ larly, by defining or by increasing or by decreasing the flow rate of the second fluid, the height of the top laminar flow in the flow cell is controlled or varied. By controlling or varying the height of the bottom and the top laminar flow, the width and/or the height and/or the longitudinal position of the sample laminar flow carrying the one or more non- spherical biological entity is controlled or varied. By de^¬ fining the width and/or the height and/or the longitudinal position of the sample laminar flow, the sample laminar flow, and thus the non-spherical biological entity, is focused i.e. moved into or positioned into the desired region of the flow cell. The differential pressure from the standing acoustic wave helps to orient the non-spherical biological entity in the desired region. The aligning of the non-spherical biolog^¬ ical entity in the desired region is achieved by focusing and orienting the non-spherical biological entity in the desired region.

In an embodiment of the method, a first side fluid is provid^¬ ed to the flow chamber such that the first side fluid

laminarly flows in the flow chamber in form of a first side laminar flow moving from the one end of the flow chamber towards the another end of the flow chamber. The first side laminar flow is sandwiched between the top laminar flow and the bottom laminar flow and between the first side wall and the sample laminar flow. Furthermore, a rate of flow of the first side fluid in the flow chamber is controlled. In the method, by controlling or varying the width of the first side laminar flow, the width and/or the height and/or the lateral position of the sample laminar flow is controlled or varied in the flow chamber i.e. by moving the sample laminar flow between the desired region and the first side wall. By defin^¬ ing the width and/or the height and/or the lateral position of the sample laminar flow, the sample laminar flow is fo^¬ cused i.e. one or more of the non-spherical biological entity is moved into or positioned into the desired region of the flow cell.

In another embodiment of the method, a second side fluid is provided to the flow chamber such that the second side fluid laminarly flows in the flow chamber in form of a second side laminar flow moving from the one end of the flow chamber towards the another end of the flow chamber. The second side laminar flow is sandwiched between the top laminar flow and the bottom laminar flow and between the second side wall and the sample laminar flow. Furthermore, a rate of flow of the second side fluid in the flow chamber is controlled. In the method, by controlling or varying the width of the second side laminar flow, the width and/or the height and/or the lateral position of the sample laminar flow is controlled or varied in the flow chamber i.e. by moving the sample laminar flow between the desired region and the second side wall. By defining the width and/or the height and/or the lateral posi^¬ tion of the sample laminar flow, the sample laminar flow is focused i.e. one or more of the non-spherical biological en^¬ tity is moved into or positioned into the desired region of the flow cell.

In another embodiment of the method, the standing acoustic wave is a standing ultrasonic wave. This provides a simple way of implementing the present method.

In another embodiment of the method, the non-spherical bio^¬ logical entity is an erythrocyte. Thus the method is used to align the erythrocyte in such a way that more of the disc side of the erythrocyte is presented for imaging and less of the sides of the erythrocyte.

A third aspect of the present technique presents a system for focusing a non-spherical biological entity carried in a sam- pie into a desired region. The system includes an imaging de^¬ vice and a flow cell. The imaging device has a field of view and the field of view includes a depth of field. The flow cell is according to as described hereinabove in the first aspect of the present technique. The desired region is aligned with the depth of field in the field of view of the imaging device. Thus, with the flow cell the non-spherical biological entity is aligned in the desired region as ex^¬ plained herein above in the first and/or the second aspect of the present technique, and since the desired region of the flow cell is aligned with or overlaps the depth of field of the imaging device, the sample, therefore the non-spherical biological entity is aligned in the depth of field of the im^¬ aging device i.e. the non-spherical biological entity is fo- cused in a desired orientation.

In an embodiment of the system, the imaging device is an in- terferometry microscopy device. Thus the aligning of the non- spherical biological entity in the depth of field of the in- terferometry microscopy device is achieved and this in turn leads to obtaining of high quality or focused images of the non-spherical biological entity in the desired orientation of the non-spherical biological entity which then may be used for post imaging analysis for example volumetric measurements of components of the non-spherical biological entity, morpho^¬ logical studies of the contents of the non-spherical biologi^¬ cal entity, and so and so forth.

In another embodiment of the system, the interferometry mi- croscopy device is a digital holographic microscopy device. This presents an advantageous example of interferometry mi^¬ croscopy device that may be used to image the non-spherical biological entity without requiring complex sample prepara^¬ tion .

The present technique is further described hereinafter with reference to illustrated embodiments shown in the accompany^¬ ing drawing, in which: schematically illustrates an exemplary embodiment of a system of the present technique; schematically illustrates an exemplary embodiment of a flow cell; schematically illustrates the exemplary embodiment of the flow cell of FIG 2 with a sample flowing; schematically illustrates an exemplary embodiment of the flow cell of the present technique; schematically illustrates an exemplary embodiment of the flow cell depicting a bottom laminar flow and a top laminar flow; schematically illustrates the embodiment of the flow cell of FIG 5 depicting an exemplary scheme for working of the flow cell; schematically illustrates an exemplary embodiment of the flow cell depicting a first side laminar flow and a second side laminar flow; schematically illustrates the embodiment of the flow cell of FIG 7 depicting an exemplary scheme for working of the flow cell; schematically illustrates an exemplary embodiment of the flow; schematically illustrates an exemplary embodiment of the flow cell of the present technique depicting an exemplary standing acoustic wave; schematically illustrates an exemplary embodiment of the flow of sample with the bottom laminar flow, the top laminar flow, the first side laminar flow and the second side laminar flow and without the standing acoustic wave; schematically illustrates a view of the non- spherical biological entity in an undesired orien tation with respect to a direction of imaging;

FIG 13 schematically illustrates the exemplary embodiment of the flow of FIG 11 with the standing acoustic wave; and

FIG 14 schematically illustrates a view of the non- spherical biological entity in a desired orienta- tion with respect to the direction of imaging; in accordance with aspects of the present technique.

Hereinafter, above-mentioned and other features of the pre^¬ sent technique are described in details. Various embodiments are described with reference to the drawing, wherein like reference numerals are used to refer to like elements

throughout. In the following description, for purpose of ex^¬ planation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodi- ments. It may be noted that the illustrated embodiments are intended to explain, and not to limit the invention. It may be evident that such embodiments may be practiced without these specific details. It may be noted that in the present disclosure, the terms "first", "second", etc. are used herein only to facilitate discussion, and carry no particular temporal or chronological significance unless otherwise indicated. The basic idea of the present technique is align a non- spherical biological entity in a desired region of a flow cell. Aligning includes focusing the non-spherical biological entity in the desired region in a flow chamber of the flow cell and orienting the non-spherical biological entity in the desired region in the flow chamber of the flow cell. In the technique the flow cell with the flow chamber having a rectangular cross-section is provided. In the flow chamber of such flow cell, the sample with its components, i.e. one or more non-spherical biological entities such as red blood cells, is flowed in a laminar flow. The laminarly flowing sample is sandwiched at least between two laminar flows, for example a top and a bottom flow. By regulating a flow rate of one or both of these laminar flows, dimensions of these lami^¬ nar flows may be influenced and since the sample laminar flow is sandwiched between these laminar flows, dimensions and po^¬ sition of the sample laminar flow are controlled within the flow chamber and thus the sample, and thereby the one or more non-spherical biological entities in the sample, is made to flow within a desired region of the flow chamber, thus focusing the non-spherical biological entity in the desired re^¬ gion. Additionally, the laminarly flowing sample may also be sandwiched between two laminar flows, say side flows that are perpendicularly aligned to the top and the bottom flows. By regulating a flow rate of one or both of these side flows, dimensions of the side flows may be influenced and since the sample laminar flow is sandwiched between the side flows in addition to the top and the bottom flows, dimensions and po- sition of the sample laminar flow are controlled within the flow chamber and thus the sample, and thereby the non- spherical biological entity is further focused in the desired region, i.e. is made to flow within the desired region of the flow chamber.

Furthermore, an acoustic transducer is used which generates a standing acoustic wave. The standing acoustic wave has a pressure node, i.e. a collection of pressure points, linearly arranged along an axis passing through the desired region. The different pressures within the flow chamber created by the standing acoustic wave acts on the non-spherical biologi^¬ cal entity and orients the non-spherical biological entity in a desired orientation i.e. in an orientation in which one a largest or substantially larger side of the non-spherical bi^¬ ological entity is presented to the imaging light, for exam^¬ ple when the non-spherical biological entity is RBC the de^¬ sired orientation is then the RBC is oriented such that a disc face of the RBC is presented to the imaging light when the RBC is focused in the desired region and arranged along the axis. Thus focusing of the non-spherical biological enti^¬ ty is achieved by regulating or controlling or defining the flow rates of the laminar flows between which the sample 1am- inar flow is sandwiched, and orienting of the non-spherical biological entity is achieved by the standing acoustic wave and particularly the pressure node. The focusing and orient^¬ ing of the non-spherical biological entity lead to aligning of the non-spherical biological entity.

FIG 1 schematically presents a system 100 of the present technique. The system 100 includes an imaging device 90 for inspecting the sample (not shown in FIG 1) and a flow cell 1 with a flow chamber 10. The imaging device 90 may have, but not limited to, a first part 92 for example an illumination source 92, and a second part 94 for example a detector with or without an interferometric unit. The imaging device 90 has a field of view 97, hereinafter the FOV 97 which represents an observable range of the imaging device 90 i.e. an object (not shown) is imaged by the imaging device 90 only when the object is positioned in the FOV 97. The imaging device 90 al^¬ so has a focus within the FOV 97. The imaging device 90 has an axis 95 along which the imaging is performed by shining a probing radiation on the object for example a Laser or a low- er-coherent light source, such as a superluminescent diode, from a direction 7 onto the object or specimen to be inspect^¬ ed by the imaging device 90.

The focus is extended according to a depth of field (not shown in FIG 1) of the imaging device 90. Thus when the ob^¬ ject is positioned in the depth of field around the focus of the imaging device 90, an ^xin-focus' image of the object is obtainable. The focus and the depth of field of the imaging device 90 in the system 1 are arranged such that the focus and the depth of field around the focus of the imaging device 90 lie or fall within the flow chamber 10. The region within the depth of field around the focus of the imaging device 90 is a region (not shown) in which the object should be ideally positioned or focused or concentrated within the flow chamber 10 for obtaining in-focus images or interference patterns of the object. The flow cell 1 has an extended channel or cavity forming the flow chamber 10 through which a specimen, for example a non- spherical biological entity such as a red blood cell (RBC) , to be imaged or inspected by the imaging device 90 is passed or flowed in a direction 8, generally perpendicular to the direction 7. The specimen or the sample to be inspected flows in the flow chamber 10 from one end 17 to another end 19 of the flow chamber 10 and the FOV 97 of the imaging device 90 is arranged such that at least a part of the flow chamber 10 between the one end 17 and the another end 19 is positioned in the FOV 97 of the imaging device 90.

Additionally, the flow cell 1 includes an acoustic transducer 80 which generates a standing acoustic wave (not shown in FIG 1) . The acoustic transducer and its functionality have been explained later in reference to FIG 10 to 14.

Referring to FIG 2 in combination with FIG 1, the flow chamber 10 has been explained further. As depicted in FIG 2, the flow chamber 10 has a rectangular cross-section when viewed from a direction (not shown) opposite to the direction 8. The flow chamber 10 includes a top wall 11, a bottom wall 12 op^¬ posite to the top wall 11, a first side wall 13 and a second side wall 14 opposite to the first side wall 13. The flow chamber 10 has a desired region 99 within the flow chamber 10. If the sample (not shown in FIG 1 and 2) is passed or flowed through the desired region 99 and if the FOV 97 and the depth of field around the focus of the imaging device 90 are arranged such that the depth of field around the focus of the imaging device 90 overlaps or aligns with the desired re- gion 99, then in-focus images or interference patterns are obtainable for part of the sample in the desired region 99 of the flow chamber 10 when imaging or inspection of the sample is performed with the imaging device 90. It may be noted that the desired region 99, hereinafter the region 99, has been schematically depicted in FIG 2 to be positioned in a center location of the cross-section of the flow chamber 10, however, it is well within the scope of the present technique that the region 99 may be present in a non-central location of the cross-section of the flow chamber 10.

FIG 3, in contrast to FIG 2, schematically presents a sample 5 flowing through the flow chamber 10. The sample 5 has non- spherical biological entities 4, for example corpuscles such as RBCs, and a fluidic carrier 6 for the non-spherical bio^¬ logical entities 4. For example, the fluidic carrier 6 may be diluted or undiluted blood plasma, a buffer, and so on and so forth. The non-spherical biological entities 4 have been hereinafter also referred to as the entity 4 or the RBC 4. When the sample 5 flows through the flow chamber 10, as de^¬ picted in FIG 3, some of the RBCs 4 are in the desired region 99 and some are outside the desired region 99. If the FOV 97 and the depth of field around the focus of the imaging device 90 are arranged such that the depth of field around the focus of the imaging device 90 overlaps or aligns with the desired region 99, then some RBCs 4 are in the FOV 97, while some of the RBCs 4 are outside the FOV 97. Furthermore, some of the RBCs 4 are in the FOV 97 but either completely or partially outside the region 99.

Referring to FIG 4, 5 and 6 in combination of FIGs 1 and 2, the flow cell 1 of the present technique is explained herein^¬ after. As shown in FIG 4, the flow cell 1, besides having the flow chamber 10 as explained in reference to FIG 2, also in- eludes a bottom flow input module 20, a sample input module

30 and a top flow input module 40. In an exemplary embodiment of the flow cell 1, the flow chamber 10 is a microfluidic channel. Furthermore, the acoustic transducer 80 is present. As mentioned hereinabove, the acoustic transducer and its functionality have been explained later in reference to FIG 10 to 14. AS shown in FIG 5 in combination with FIG 4, the bottom flow input module 20 receives a first fluid (not shown) and pro^¬ vides the first fluid to the flow chamber 10. The bottom flow input module 20, hereinafter also referred to as the module 20, provides the first fluid, for example water, to the flow chamber 10 in such a way that the first fluid laminarly flows along the bottom wall 12 in the flow chamber 10 from the one end 17 (shown in FIG 1) of the flow chamber 10 towards the another end 19 (shown in FIG 1) of the flow chamber 10. The laminarly flowing first fluid forms a bottom laminar flow 72. The bottom flow input module 20 controls a rate of flow of the first fluid in the flow chamber 10. The term ^control' as used herein includes defines or decides, restricts, sets up, increases and/or decreases the rate of flow of the first flu^¬ id in the flow chamber 10 forming the bottom laminar flow 72, hereinafter also referred to as the flow 72. Forming laminar flow of fluids in a flow chamber is a well known technique in the field of hydrodynamics or fluid dynamics and has not been described herein in details for sake of brevity. The module 20 may include, but not limited to, flow channels, valves, pumps, flow meters, etc. The flow 72 may be understood as a rectangular parallelepiped shaped flow extending along the direction 8 in the flow chamber 10 and contiguous with the bottom wall 12. The top flow input module 40 receives a second fluid (not shown) and provides the second fluid to the flow chamber 10. The top flow input module 40, hereinafter also referred to as the module 40, provides the second fluid, for example water, to the flow chamber 10 in such a way that the second fluid laminarly flows along the top wall 11 in the flow chamber 10 from the one end 17 (shown in FIG 1) of the flow chamber 10 towards the another end 19 (shown in FIG 1) of the flow cham^¬ ber 10. The laminarly flowing second fluid forms a top lami- nar flow 71. The top flow input module 20 controls a rate of flow of the second fluid in the flow chamber 10. The term ^control' as used herein includes defines or decides, re^¬ stricts, sets up, increases and/or decreases the rate of flow of the second fluid in the flow chamber 10 forming the top laminar flow 71, hereinafter also referred to as the flow 71. The module 40 may include, but not limited to, flow channels, valves, pumps, flow meters, etc. The flow 71 may be under^¬ stood as a rectangular parallelepiped shaped flow extending along the direction 8 in the flow chamber 10 and contiguous with the top wall 11.

The sample input module 30 receives the sample 5 and provides the sample 5 to the flow chamber 10. The sample input module 30, hereinafter also referred to as the module 30, provides the sample 5 to the flow chamber 10 in such a way that the sample 5 laminarly flows sandwiched between the flow 71 and the flow 72 from the one end 17 (shown in FIG 1) of the flow chamber 10 towards the another end 19 (shown in FIG 1) of the flow chamber 10. The laminarly flowing sample 5 forms a sample laminar flow 75. The sample input module 30 controls a rate of flow of the sample 5 in the flow chamber 10. The term ^control' as used herein includes defines or decides, re^¬ stricts, sets up, increases and/or decreases the rate of flow of the sample 5 in the flow chamber 10 forming the sample laminar flow 75, hereinafter also referred to as the flow 75. The module 30 may include, but not limited to, flow channels, valves, pumps, flow meters, etc. The flow 75 may be under^¬ stood as a rectangular parallelepiped shaped flow extending along the direction 8 in the flow chamber 10 and sandwiched between the flow 71 and the flow 72.

In the flow chamber 10, by defining or setting up or by increasing or by decreasing the flow rate of the first fluid, the height of the flow 72 is fixed or controlled or varied. Similarly, by defining or setting up or by increasing or by decreasing the flow rate of the second fluid, the height of the flow 71 is fixed or controlled or varied. In the flow cell 1, by controlling or varying the height of the flow 71 and/or the flow 72, the width and/or the height and/or the longitudinal position of the flow 75 is controlled or varied. For example as schematically depicted in FIG 5, the flow 75 is now restricted to or concentrated in or fo^¬ cused at least partly in the region 99. In an exemplary em^¬ bodiment (not shown) of the flow cell 1, the desired region 99 extends from the first side wall 13 to the second side wall 14 and then the flow 75 is substantially positioned in the desired region 99, thereby the RBCs 4 are focused in the desired region 99.

As depicted in FIG 6, an exemplary working of the flow cell 1 has been schematically depicted. If relative heights of the flow 71 and the flow 72 are such that the flow 75 is below or beneath the desired region 99, as shown in FIG 6, then by controlling the flow rates of the first and the second fluids for example by increasing the flow rate of the first fluid via the module 20 and/or decreasing the flow rate of the se^¬ cond fluid via module 40 the relative heights of the flow 72 and the flow 71 are altered thereby bringing the flow 75 at least partly in the region 99, as shown in FIG 5. Alterna^¬ tively, if relative heights of the flow 71 and the flow 72 are such that the flow 75 is above (not shown) the desired region 99 then by controlling the flow rates of the first and the second fluids for example by decreasing the flow rate of the first fluid via the module 20 and/or increasing the flow rate of the second fluid via module 40 the relative heights of the flow 72 and the flow 71 are altered thereby bringing the flow 75 at least partly in the region 99. In short the height of the sample laminar flow 75 and/or the longitudinal position of the sample laminar flow 75 is decided or fixed or adjusted by altering the flow rates of the first and/or the second fluids via the modules 20 and/or 40.

Referring to FIG 4 in combination with FIGs 7 and 8, other exemplary embodiments of the flow cell 1 have been explained hereinafter. In an embodiment of the flow cell 1 a first side flow input module 50, hereinafter the module 50, is included. The module 50 receives a first side fluid (not shown) and provides the first side fluid to the flow chamber 10. The first side fluid, for example water, is provided by the mod^¬ ule 50 in such a way that the first side fluid laminarly flows along the first side wall 13 in the flow chamber 10 from the one end 17 (shown in FIG 1) of the flow chamber 10 towards the another end 19 (shown in FIG 1) of the flow cham- ber 10. The laminarly flowing first side fluid forms a first side laminar flow 73, hereinafter also referred to as the flow 73. The flow 73 is sandwiched between the flow 71 and the flow 72 and between the first side wall 13 and the flow 75, as shown in FIG 7.

The module 50 controls a rate of flow of the first side fluid in the flow chamber 10. The term ^control' as used herein includes defines or decides, restricts, sets up, increases and/or decreases the rate of flow of the first side fluid in the flow chamber 10 forming the flow 73. The module 50 may include, but not limited to, flow channels, valves, pumps, flow meters, etc. The flow 73 may be understood as a rectan^¬ gular parallelepiped shaped flow extending along the direc^¬ tion 8 in the flow chamber 10 and contiguous with a part of the first side wall 13 on one face and the flow 75 on the op^¬ posite face, and also contiguous on another face with flow 71 and on a face opposite to the another face with the flow 72.

In another embodiment of the flow cell 1 a second side flow input module 60, hereinafter also referred to as the module 60, is included. The module 60 receives a second side fluid (not shown) and provides the second side fluid to the flow chamber 10. The second side fluid, for example water, is pro^¬ vided by the module 60 in such a way that the second side fluid laminarly flows along the second side wall 14 in the flow chamber 10 from the one end 17 (shown in FIG 1) of the flow chamber 10 towards the another end 19 (shown in FIG 1) of the flow chamber 10. The laminarly flowing second side fluid forms a second side laminar flow 74, hereinafter also referred to as the flow 74. The flow 74 is sandwiched between the flow 71 and the flow 72 and between the second side wall 14 and the flow 75, as shown in FIG 7.

The module 60 controls a rate of flow of the second side flu^¬ id in the flow chamber 10. The term ^control' as used herein includes defines or decides, restricts, sets up, increases and/or decreases the rate of flow of the second side fluid in the flow chamber 10 forming the flow 74. The module 60 may include, but not limited to, flow channels, valves, pumps, flow meters, etc. The flow 74 may be understood as a rectan^¬ gular parallelepiped shaped flow extending along the direc^¬ tion 8 in the flow chamber 10 and contiguous with a part of the second side wall 14 on one face and the flow 75 on the opposite face, and also contiguous on another face with flow

71 and on a face opposite to the another face with the flow

72.

In the flow chamber 10, by defining or setting up or by increasing or by decreasing the flow rate of the first side fluid, the width of the flow 73 is fixed or controlled or varied. Similarly, by defining or setting up or by increasing or by decreasing the flow rate of the second side fluid, the width of the flow 74 is fixed or controlled or varied. In the flow cell 1, by controlling or varying the width of the flow

73 and/or the flow 74, the width and/or the height and/or the lateral position of the flow 75 is controlled or varied. For example as schematically depicted in FIG 7, the flow 75, and thus the RBCs 4, is now restricted to or concentrated in or focused in the region 99.

As depicted in FIG 8, an exemplary working of the flow cell 1 has been schematically depicted. If relative widths of the flow 73 and the flow 74 are such that the flow 75 is at least partly shifted from the desired region 99 towards the second side wall 14, as shown in FIG 8, then by controlling the flow rates of the first side and/or the second side fluids for ex- ample by increasing the flow rate of the second side fluid via the module 60 and/or decreasing the flow rate of the first side fluid via module 50 the relative widths of the flow 74 and the flow 73 are altered thereby bringing the flow 75 in the region 99, as shown in FIG 7. Alternatively, if relative widths of the flow 73 and the flow 74 are such that the flow 75 is shifted (not shown) to the other side of the the desired region 99 i.e. towards the first side wall 13, then by controlling the flow rates of the first side and the second side fluids for example by increasing the flow rate of the first side fluid via the module 50 and/or decreasing the flow rate of the second fluid via module 60 the relative widths of the flow 73 and the flow 74 are altered thereby bringing the flow 75 in the region 99, as shown in FIG 7. In short the width of the sample laminar flow 75 and/or the lat^¬ eral position of the sample laminar flow 75 is decided or fixed or adjusted by altering the flow rates of the first side and/or the second side fluids via the modules 50 and/or 60.

As shown in FIG 4, in another embodiment of the flow cell 1, a flow exit 79 is present for allowing the flows 71, 72, 73, 74 and 75 to exit the flow chamber 10. In presence of the flows 71, 72, 73, 74 covering flow 75 on all sides, the RBCs 4 are physically removed from the walls 11, 12, 13 and 14 and thus never in contact with the walls 11, 12, 13 and 14 and therefore none of the RBCs 4 adhere to the walls 11, 12, 13 or 14 and disintegration of the RBCs 4 to form debris is avoided .

FIG 9 depicts the flows 71, 72, 73, 74, 75 and the flow di^¬ rection 8. The acoustic transducer 80, hereinafter also referred to as the transducer 80, may be positioned such that a part of the transducer 80 is in direct physical contact with one or more of the flows 71, 72, 73, 74, for example the flow 72 as shown in FIG 9. Alternatively, as depicted in FIGs 1 and 4, the transducer 80 may be positioned such that a part of the transducer 80 is in direct physical contact, for exam- pie by fixing such as by gluing, with one or more of the walls 11, 12, 13, 14 and outside the flow chamber 10. In an^¬ other embodiment (not shown) , the transducer 80 may even be positioned physically removed i.e. not touching any of the walls 11, 12, 13, 14.

FIG 10 shows the acoustic transducer 80. The transducer 80 generates a standing acoustic wave 82 having a pressure node 88 linearly arranged along the axis 9. The axis 9 passes through the desired region 99. The pressure node 88 of the standing acoustic wave 82 may includes a collection of pres^¬ sure points (not shown) that are substantially linearly ar^¬ ranged along the axis 9. The transducer 80 may be a ultrason^¬ ic transducer for example a piezoelectric ceramic, also called piezoceramic or piezoacoustic transducers (PZT) . Such transducers 80 and their functionality are known in the field of wave propagation sciences and thus not described in de^¬ tails herein for sake of brevity. Although the standing wave 82 is shown to form just in one direction in FIG 10, it may be noted that standing wave may also form in other directions (not shown) , preferably in a direction perpendicular to the standing wave 82.

FIG 11 and 13 represent cases where the RBC 4 has been fo- cused or concentrated in the region 99. The region 99 is shown to be overlapping with the depth of field 98 in the FOV 97. In an embodiment of the flow cell 1, the sample laminar flow 75 is regulated by regulating the flow rates of one or more of the flows 71, 72, 73, 74, 75 such that the RBCs 4 are in a two-dimensional (2D) flow. As shown in FIG 11 in absence of acoustic forces resulting from the standing acoustic wave 82 generated by the transducer 80, the RBC 4 though in the region 99 may be oriented to show up-ended side toward the axis 95 when viewed along the direction 7 as shown in FIGs 11 and 12. When the RBC 4 is in side showing orientation as depicted by FIGs 11 and 12 i.e. when the RBC 4 presents side to the axis 95 when viewed in the direction 7 the image or in^¬ terference patterns obtained present less morphological fea- tures and are less useful for volumetric analysis as compared to a case when the RBC 4 in an orientation when the RBC 4 presents disc face or flat side to the axis 95 when viewed in the direction 7.

As shown in FIG 13 when the transducer 80 generates the wave 82 acoustic forces resulting from the wave 82 orient the RBC 4 such that the RBC 4 rotates and is oriented to show flat face or disc face toward the axis 95 when viewed along the direction 7 as shown in FIGs 13 and 14. When the RBC 4 is in disc face showing orientation as depicted by FIGs 13 and 14 i.e. when the RBC 4 presents disc face or flat face to the axis 95 when viewed in the direction 7 the image or interference patterns obtained present more morphological features and are more useful for volumetric analysis as compared to a case when the RBC 4 in the orientation shown in FIGs 11 and 12. The flow chamber 10 serves as a conduit for the flows 71, 72, 73, 74 and 75 and at the same time acts as an acoustic resonator defined by the flow chamber 10 dimension. The RBC 4 exposed to an acoustic force resulting from the standing acoustic wave 82 in the flow chamber 10 will be orientated such that a net acoustic force acting on the RBC 4 is mini^¬ mized, for example the RBC will be oriented substantially parallel to the top wall 11 and the bottom wall 12, for the embodiment depicted in FIG 13.

It may be noted that although FIGs 1, 4, 9 and 10 depict only one transducer 80, it is well within the scope of the present technique to have more than one transducer 80. Each of the multiple transducers 80 may be actuated by individual elec^¬ tric signals which may be same or different. It may be noted that the imaging device 90 (shown in FIG 1) may perform counting and imaging of the RBCs 4, and when performing both imaging and counting, only few RBCs 4 may be desired to be oriented and not all as representative specimens of the RBCs 4 in the sample 5. It may also be noted that when the standing wave 82 forms in two directions (not shown) or to say in two dimensions, the RBC 4 rotates and aligns itself in an orientation in which the RBC 4 presents its smallest dimension parallel with the strongest acoustic force out of the two acoustic forces from the two directions. Thus besides the pressure node 88, anoth^¬ er pressure node (not shown) is formed. The frequencies for generating the standing waves from two different sides are essentially different frequencies, and the frequency used to generate the standing wave 82, and thus the node 88, domi^¬ nates resulting into the orientation effect wherein the largest acoustic force acting on the focused RBC 4 causes the orientation effect on the RBC 4 i.e. small side of RBC 4 aligned parallel to the largest acoustic force direction.

As shown in FIG 1, the system 100 includes the imaging device 90. In one embodiment of the system 100, the second part 94 of the imaging device 90 includes an interferometry unit (not shown) and a detector (not shown) . The interferometry unit may be a common path interferometry unit or different path interferometry unit. In common path interferometry unit, a light beam is shone or impinged on the sample 5 from the first part 92 of the imaging device 90 and then the light beam emerging after interacting with the sample 5 is split into a reference beam (not shown) and an object beam (not shown) . Subsequently, object information is filtered out or deleted from the reference beam and then the filtered refer^¬ ence beam is superimposed with the object beam to detect the interference pattern at the detector. In different path in- terferometry unit, a light beam to be incident on the sample 5 is first split into an object beam (not shown) and a refer^¬ ence beam (not shown) i.e. the light beam is split into the reference beam and the object beam before interacting with the sample 5. The object beam is then shone or impinged upon the sample 5 but the reference beam is directed to another optical path (not shown) within the different path

interferometric unit and is not shone or impinged upon the sample 5, i.e. the RBC 4. Subsequently, the object beam car- rying object information is superimposed with the reference beam to obtain interference pattern at the detector. The interference pattern obtained as an output of the common path or different path interferometry is analyzed. The interfer- ence pattern also referred to as image of the RBC 4 repre^¬ sents characteristics of the RBC 4 such as physical struc^¬ tures in the RBC 4, morphology of the RBC 4, and so on and so forth. Designs, setups and principle of working of the common path interferometry and the different path interferometry are known in the field of interferometric microscopy and not de^¬ scribed herein in details for sake of brevity.

The present technique also encompasses a method for aligning, i.e. focusing and orienting, the RBC 4 in the sample 5 into the desired region 99 in the flow cell 1. The flow cell 1 is same as the flow cell 1 described in reference to FIGs 1 to 10 and presented in accordance with the first aspect of the present technique. In the method, the first fluid, the second fluid and the sample 5 carrying one or more of the RBCs 4 are provided to the flow chamber 10. The first fluid, the second fluid and the sample 5 may be provided either simultaneously or sequentially in any order. The first fluid is provided to the flow chamber 10 such that the first fluid laminarly flows along the bottom wall 12 in the flow chamber 10 from one end 17 of the flow chamber towards another end 19 of the flow chamber 10. The laminarly flowing first fluid forms the bot^¬ tom laminar flow 72, as described hereinabove with reference to FIGs 1 to 14. The second fluid is provided to the flow chamber 10 such that the second fluid laminarly flows along the top wall 11 in the flow chamber 10 from the one end 17 of the flow chamber 10 towards the another end 19 of the flow chamber 10. The laminarly flowing second fluid forms the top laminar flow 71, as described hereinabove with reference to FIGs 1 to 14. The sample 5 is provided to the flow chamber 10 such that the sample 5 laminarly flows in the flow chamber 10 in form of the sample laminar flow 75 from the one end 17 of the flow chamber 10 towards the another end 19 of the flow chamber 10. The laminarly flowing sample 5 forms the sample laminar flow 75, as described hereinabove with reference to FIGs 1 to 14. The flow 75 is sandwiched between the flow 71 and the flow 72. In the method, a rate of flow of the first fluid and a rate of flow of the second fluid in the flow chamber 10 are con^¬ trolled. In the method, by defining or setting or fixing or by increasing or by decreasing the flow rate of the first and/or the second fluid, the height of the flow 72 and/or the flow 71 in the flow cell 10 is controlled or varied which in turn effects the width and/or the height and/or the longitu^¬ dinal position of the flow 75 which is thereby controlled or varied by controlling the flow rates of the first and the se^¬ cond fluids. By defining the width and/or the height and/or the longitudinal position of the flow 75, the flow 75, and thereby the RBC 4, is focused i.e. moved into or positioned into the desired region 99 of the flow cell 1. In the method, the desired region 99 is aligned, as shown in FIGs 11 and 13, with the depth of field 98 in the field of view 97 of the im- aging device 90 shown in FIG 1. The standing acoustic wave 82 having the pressure node 88 is generated. The pressure node 88 of the standing acoustic wave 82 is linearly arranged along the axis 9 passing through the desired region 99 to orient the non-spherical biological entity 4 carried in the sample 5 into the desired region 99.

In an exemplary embodiment of the method, the first side flu^¬ id is provided to the flow chamber 10 to form the flow 73, and the rate of flow of the first side fluid in the flow chamber 10 is controlled. The providing of the first side laminar flow 73 and controlling the rate of flow of the first side laminar flow 73 is same as described hereinabove with reference to FIGs 1 to 14. In another exemplary embodiment of the method, the second side fluid is provided to the flow chamber 10 to form the flow 74, and the rate of flow of the second side fluid in the flow chamber 10 is controlled. The providing of the second side laminar flow 74 and controlling the rate of flow of the second side laminar flow 74 is same as described hereinabove with reference to FIGs 1 to 14.

By controlling or varying the width of the flow 73 and/or the flow 74, the width and/or the height and/or the lateral posi^¬ tion of the flow 75 in the flow chamber 10 is controlled or varied, and thus the flow 75, and thereby the RBC 4, is fo^¬ cused i.e. moved into or positioned into the desired region 99 of the flow cell 1.

While the present technique has been described in detail with reference to certain embodiments, it should be appreciated that the present technique is not limited to those precise embodiments. Rather, in view of the present disclosure which describes exemplary modes for practicing the invention, many modifications and variations would present themselves, to those skilled in the art without departing from the scope and spirit of this invention. The scope of the invention is, therefore, indicated by the following claims rather than by the foregoing description. All changes, modifications, and variations coming within the meaning and range of equivalency of the claims are to be considered within their scope.

Claims

Patent claims

1. A flow cell (1) for aligning a non-spherical biological entity (4) carried in a sample (5) into a desired region (99) in the flow cell (1), the non-spherical biological entity (4) to be inspected by an imaging device (90), the flow cell (1) comprising :

- a flow chamber (10) having a rectangular cross-section, a top wall (11), a bottom wall (12) opposite to the top wall

(11), a first side wall (13), a second side wall (14) oppo^¬ site to the first side wall (13) and the desired region (99);

- a bottom flow input module (20) configured to receive a first fluid and to provide the first fluid to the flow cham^¬ ber (10) such that the first fluid laminarly flows in the flow chamber (10) in form of a bottom laminar flow (72) along the bottom wall (12) from one end (17) of the flow chamber (10) towards another end (19) of the flow chamber (10), wherein the bottom flow input module (20) is further configured to control a rate of flow of the first fluid in the flow chamber (10) ;

- a top flow input module (40) configured to receive a second fluid and to provide the second fluid to the flow chamber

(10) such that the second fluid laminarly flows in the flow chamber (10) in form of a top laminar flow (71) along the top wall (11) from one end (17) of the flow chamber (10) towards another end (19) of the flow chamber (10), wherein the top flow input module (40) is further configured to control a rate of flow of the second fluid in the flow chamber (10);

- a sample input module (30) configured to receive the sample (5) and to provide the sample (5) to the flow chamber (10) such that the sample (5) laminarly flows in the flow chamber (10) in form of a sample laminar flow (75) from one end (17) of the flow chamber (10) towards another end (19) of the flow chamber (10) and the sample laminar flow (75) is sandwiched between the top laminar flow (71) and the bottom laminar flow (72 ) ; and

- an acoustic transducer (80) configured to generate a stand- ing acoustic wave (82) having a pressure node (88) linearly arranged along an axis (9) passing through the desired region (99) .

2. The flow cell (1) according to claim 1, comprising:

- a first side flow input module (50) configured to receive a first side fluid and to provide the first side fluid to the flow chamber (10) such that the first side fluid laminarly flows in the flow chamber (10) in form of a first side lami^¬ nar flow (73) sandwiched between the top laminar flow (71) and the bottom laminar flow (72) and between the first side wall (13) and the sample laminar flow (75), wherein the first side flow input module (50) is further configured to control a rate of flow of the first side fluid in the flow chamber (10) and wherein the first side laminar flow (73) moves from the one end (17) of the flow chamber (10) towards the another end (19) of the flow chamber (10) .

3. The flow cell (1) according to claim 1 or 2, further comprising :

- a second side flow input module (60) configured to receive a second side fluid and to provide the second side fluid to the flow chamber (10) such that the second side fluid

laminarly flows in the flow chamber (10) in form of a second side laminar flow (74) sandwiched between the top laminar flow (71) and the bottom laminar flow (72) and between the second side wall (14) and the sample laminar flow (75), wherein the second side flow input module (60) is further configured to control a rate of flow of the second side fluid in the flow chamber (10) and wherein the second side laminar flow (74) moves from the one end (17) of the flow chamber

(10) towards the another end (19) of the flow chamber (10) .

4. The flow cell (1) according to any of claims 1 to 3, wherein the sample input module (30) is configured to control a rate of flow of the sample (5) in the flow chamber (10) .

5. The flow cell (1) according to any of claims 1 to 4, wherein the flow chamber (10) is a microfluidic channel.

6. The flow cell (1) according to any of claims 1 to 5, wherein the acoustic transducer (80) is an ultrasonic trans- ducer and wherein the standing acoustic wave (82) is a stand^¬ ing ultrasonic wave.

7. The flow cell (1) according to claim 6, wherein the ultrasonic transducer (80) is a piezoelectric ceramic.

8. A method for aligning a non-spherical biological entity (4) carried in a sample (5) into a desired region (99) in a flow cell (1), the non-spherical biological entity (4) to be inspected by an imaging device (90) having a depth of field (98) in a field of view (97) of the imaging device (90), the flow cell (1) comprising a flow chamber (10) having a rectangular cross-section, a top wall (11), a bottom wall (12) op^¬ posite to the top wall (11), a first side wall (13), a second side wall (14) opposite to the first side wall (13) and the desired region (99); the method comprising:

- providing a first fluid to the flow chamber (10) such that the first fluid laminarly flows in the flow chamber (10) in form of a bottom laminar flow (72) along the bottom wall (12) from one end (17) of the flow chamber (10) towards another end (19) of the flow chamber (10);

- providing a second fluid to the flow chamber (10) such that the second fluid laminarly flows in the flow chamber (10) in form of a top laminar flow (71) along the top wall (11) from the one end (17) of the flow chamber (10) towards the another end (19) of the flow chamber (10); - providing the sample (5) to the flow chamber (10) such that the sample (5) comprising the non-spherical biological entity (4) laminarly flows in the flow chamber (10) in form of a sample laminar flow (75) from the one end (17) of the flow chamber (10) towards the another end (19) of the flow chamber (10) and wherein the sample laminar flow is sandwiched be^¬ tween the top laminar flow (71) and the bottom laminar flow (72) ; - controlling a rate of flow of the first fluid and/or a rate of flow of the second fluid in the flow chamber (10) to focus the sample carrying the non-spherical biological entity (4) into the desired region (99); - aligning the desired region (99) with the depth of field (98) in the field of view (97) of the imaging device (90); and

- generating a standing acoustic wave (82) having a pressure node (88), wherein the pressure node (88) of the standing acoustic wave (82) is linearly arranged along an axis (9) passing through the desired region (99) to orient the non- spherical biological entity (4) carried in the sample (5) in^¬ to the desired region (99) .

9. The method according to claim 8, comprising:

- providing a first side fluid to the flow chamber (10) such that the first side fluid laminarly flows in the flow chamber (10) in form of a first side laminar flow (73) sandwiched be- tween the top laminar flow (71) and the bottom laminar flow

(72) and between the first side wall (13) and the sample lam^¬ inar flow (75) from the one end (17) of the flow chamber (10) towards the another end (19) of the flow chamber (10); and

- controlling a rate of flow of the first side fluid in the flow chamber (10) .

10. The method according to claim 8 or 9, comprising: - providing a second side fluid to the flow chamber (10) such that the second side fluid laminarly flows in the flow cham^¬ ber (10) in form of a second side laminar flow (74) sandwiched between the top laminar flow (71) and the bottom lami- nar flow (72) and between the second side wall (14) and the sample laminar flow (75) from the one end (17) of the flow chamber (10) towards the another end (19) of the flow chamber (10); and

- controlling a rate of flow of the second side fluid in the flow chamber (10) .

11. The method according to any of claims 8 to 10, wherein the standing acoustic wave (82) is a standing ultrasonic wave .

12. The method according to any of claims 8 to 11, wherein the non-spherical biological entity (4) is an erythrocyte.

13. A system (100) for aligning a non-spherical biological entity (4) carried in a sample (5) into a desired region

(99), the system (100) comprising:

- an imaging device (90) having a field of view (97), wherein the field of view (97) includes a depth of field (98); and

- a flow cell (1) according to any of claims 1 to 7, and wherein the desired region (99) is aligned with the depth of field (98) in the field of view (97) of the imaging device (90) .

14. The system (100) according to claim 13, wherein the imag- ing device (90) is an interferometry microscopy device.

15. The system (100) according to claim 14, wherein the interferometry microscopy device is a digital holographic mi^¬ croscopy device.