CN109946217A - An acoustically driven flow cytometry device - Google Patents

Abstract

This application discloses a kind of sound-driving flow cytometry detection devices, including cell operational module, image-forming module and image processing module, cell operational module includes flow chamber and ultrasonic radiation force generating system, ultrasonic radiation force generating system is used to generate acoustic radiation force to cell granulations, manipulation cell particle is arranged in parallel lines, it realizes that multirow focuses, cell granulations is made to suspend, while cell granulations directed transport to detection zone being driven to realize multi-channel parallel detection.Since the application is transported and focused using the realization of acoustic radiation force manipulation cell particle, there is no need to complicated pumping system drive control fluids, without introducing sheath fluid；The virtual channel arranging cells that the application utilizes acoustic radiation force to constitute avoid the problem of cavity blocks；Since acoustic radiation force can arrange multirow cell, it is achieved that the multi-channel parallel processing that multirow focuses；It since flow chamber is low in cost, can replace every time, therefore avoid the problem of residue pollutes new samples in runner.

Description

An acoustically driven flow cytometry device

technical field

The present application relates to a flow cytometry detection device, in particular to an acoustically driven flow cytometry detection device.

Background technique

A flow cytometer is a device that automatically analyzes and sorts cells. The flow chamber and fluidic drive system are the key components of the flow cytometer. The flow chamber is composed of a sample tube, a sheath liquid tube and a nozzle. It is usually made of transparent and stable materials such as optical glass and quartz. The sample tube stores the sample, and the single cell suspension is ejected from the sample tube under the action of the liquid flow pressure; the sheath fluid flows from the sheath fluid tube to the nozzle hole, and is ejected from the nozzle after surrounding the periphery of the sample. Due to the action of the sheath fluid, the cells to be detected are confined to the axis of the fluid flow.

Therefore, the current flow cytometer mainly uses hydrodynamic force to realize the transport and flow focusing of cell particles in the microfluidic channel. This technical solution mainly has the following problems: suspended particles are easy to block the microchannel, and the cost of replacing the channel is relatively high. High; flow focusing experiments require expensive sheath fluid to constrain cells to be arranged in a single column; complex and expensive microfluidic pump systems are required to drive fluid flow; current flow cytometers are mainly single-channel processing, rather than multi-channel parallel processing It is not easy to clean, and the residual sample in the flow channel will contaminate the new sample.

The current flow cytometer mainly uses the hydrodynamic force to realize the transport and flow focusing of the cells waiting to be detected in the microfluidic channel. In order to make the fluid flow, an air compression pump is usually used to compress the air to provide the necessary pressure for the fluid flow, and the pressure of the liquid flow is stabilized by a pressure regulator, so as to form a steady flow, so that the sample particles can flow into the flow chamber at a uniform speed. However, the gas circuit and control method involved in such a pump system are very complicated, many parts are required, and the assembly volume of the system is huge.

Flow focusing is a key module of flow cytometry. Usually, sheath fluid focusing is used to form a wrapping and squeezing effect on the sample flow, focusing the sample flow at the center of the channel, and sandwiching the cell particles in the sample flow into a linear arrangement. , so that the cell particles pass through the detection zone one by one. The introduction of the sheath liquid flow in this method increases the introduction amount of the overall liquid, and increases the complexity of the entire liquid flow control system. In addition, the sheath liquid is also an expensive consumable.

Another method does not require the use of sheath fluid, and focuses the cells through the external field force or the fluid force in the channel, so that the cells pass through the detection area one by one. The patents "A Microfluidic Chip and Its Preparation Method and Application" (Application No. 201611146452.6) and "A Particle Sorting Method and its Device and Use" (Application No. 201710016125.7) use an external standing wave sound field to arrange cell particles into a line Or multiple lines, to achieve single-column or multi-column focusing, so that cells pass through the detection area one by one. It has also been reported in the literature that the cell particles are focused by using fluid forces such as the backflow force after fluid separation, the fluid inertial lift force, the vortex utility force, and the inertial Dean flow lift force, respectively. Although this method does not require the introduction of an external force field, it requires precise control of the liquid, which increases the complexity of the system. The patent publication No. US2009/0042241A1 adopts the constricting type sheathless flow cell particle focusing method, but its fluid channel is easily blocked by large particles. Additionally, these methods still require complex pump systems to power fluid-transport cells.

Most of the current flow cytometers are single-channel focused processing methods. In order to improve throughput, flow cytometers with multi-channel parallel processing methods have also been reported in patent documents. The patent "a microfluidic chip and its preparation method and application" (application number 201611146452.6) uses the standing wave fields generated by multiple transducers to arrange cells into multiple lines, realizing multi-column focusing and parallel processing. The patent "System and Method for Measuring Multiple Emissions from Multiple Parallel Flow Channels in a Flow Cytometry System" (Application No. 201080027480.0) discloses a flow cytometer system with multiple parallel flow channels to improve The system detects the number of cells per second.

The common shortcomings of the prior art mainly include the following three points:

All need to use a complex pump system to drive the fluid, and the cost of the fluid drive system is high;

The transportation, focusing and detection of the particles need to be carried out in a single or multiple micro-channels, and the suspended cell particles in the channel can easily block the channel, making the system ineffective, and the replacement cost is high;

Not easy to clean, residual samples in the flow cell and fluidics can contaminate new samples.

SUMMARY OF THE INVENTION

The technical problem to be solved by this application is to provide an acoustically driven flow cytometry detection device in view of the deficiencies of the prior art.

The technical problem to be solved by this application is solved by the following technical solutions:

An acoustically driven flow cytometry detection device, comprising a cell manipulation module, an imaging module and an image processing module, the cell manipulation module is used for manipulating cell particles in a sample solution, and the imaging module is used for staining the cell particles Fluorescence imaging is performed, the image processing module is used for processing and analyzing the fluorescence images, counting the cell particles and estimating the size of the cell particles, the cell manipulation module includes a flow chamber and an ultrasonic radiation force generating system, and the flow chamber is used for containing Put the sample solution containing cell particles; the ultrasonic radiation force generation system is used to generate acoustic radiation force on the cell particles, control the cell particles to be arranged into parallel lines, realize multi-line focusing, suspend the cell particles, and drive the directional transport of the cell particles at the same time To the detection area to achieve multi-channel parallel detection.

The ultrasonic radiation force generating system includes a radiation force generating mechanism, a signal generator and a power amplifier. After the electrical signal generated by the signal generator is amplified by the power amplifier, the radiation force generating mechanism is excited to generate ultrasonic waves and then generate radiation to the particles. force to transport and manipulate cells.

The flow chamber includes a substrate, PDMS sidewalls and a glass top cover, the PDMS sidewalls are bonded to the substrate and the glass top cover, respectively, and the substrate is made of quartz glass, plexiglass or silicon.

The radiation force generating mechanism includes an ultrasonic transducer and an artificial structure placed in the flow chamber. The electric signal amplified by the power amplifier excites the ultrasonic transducer to generate ultrasonic waves and further generates radiation force to the particles.

The artificial structure includes an artificial periodic structure or an artificial aperiodic structure.

The artificial periodic structure includes a substrate and a plurality of protruding strips arranged on the lower surface of the substrate, and the protruding strips are arranged in parallel and at equal intervals.

The ultrasonic transducer is disposed outside the flow chamber, and the ultrasonic transducer does not coincide with the geometric center of the artificial periodic structure.

The radiative force generating mechanism includes a plurality of transducers positioned outside the flow chamber for synthesizing the sound field.

The plurality of transducers include at least one ultrasonic transducer and interdigital transducers arranged in pairs and arranged in parallel, the interdigital transducers are used to synthesize a standing wave field to align cells to achieve focusing, and the ultrasonic transducers The device is used to generate a biased Gaussian beam for cell transport.

Due to the adoption of the above technical solutions, the beneficial effects of the present application are:

In a specific embodiment of the present application, since it includes a cell manipulation module, an imaging module and an image processing module, the cell manipulation module includes a flow chamber and an ultrasonic radiation force generation system, and the flow chamber is used to hold a sample solution containing cell particles; ultrasonic radiation The force generation system is used to generate acoustic radiation force on cell particles, control the arrangement of cell particles into parallel lines, realize multi-row focusing, suspend cell particles, and drive cell particles to be transported to the detection area to achieve multi-channel parallel detection. Since the application uses the acoustic radiation force to manipulate the cell particles to achieve transport and focusing, there is no need for a complex pump system to drive the control fluid, nor to introduce sheath fluid; because the application uses the acoustic radiation force to arrange the cells in a virtual channel, there is no need to present There are micro flow channels used in the technology, so the problem of channel blockage is avoided; due to the acoustic radiation force can arrange multiple rows of cells, multi-channel parallel processing of multiple rows of focusing is realized; The flow chamber and other components have low cost and simple process, and can be replaced with new devices every time a new sample is measured, thus avoiding the problem of contamination of new samples by residues in the flow channel in the prior art. In conclusion, the present application provides a low-cost flow cytometry detection solution without microfluidic channel, without microfluidic pump, without sheath fluid, which can be discarded, can be processed in parallel.

Description of drawings

FIG. 1 is a schematic diagram of functional modules of the device of the present application in one embodiment;

2 is a schematic structural diagram of the artificial cycle structure of the application in one embodiment;

Fig. 3 is the transmission spectrum of the artificial periodic structure shown in Fig. 2;

Fig. 4 is the distribution along the x direction of the artificial periodic structure modulation sound field;

Figure 5 shows that the cells are subjected to acoustic radiation forces in three directions of x, y, and z in the artificial structure sound field;

Figure 6 shows the sound pressure field distribution and the directions of the radiation force components Fy and Fz when the artificial periodic structure resonates in the yz plane;

Fig. 7 is the distribution of radiation force components Fy and Fz along the y direction when the artificial periodic structure resonates in the yz plane;

Figure 8 shows the sound pressure field distribution and the directions of the radiation force components Fy and Fz when the artificial periodic structure is non-resonant in the yz plane;

Figure 9 shows the distribution of the sound pressure field and the distribution of the radiation force components Fy and Fz along the y direction when the artificial periodic structure is non-resonant in the yz plane;

Figure 10 is the distribution of the acoustic radiation force components Fx and Fz along the transport direction x;

FIG. 11 is an image acquired using the acoustically driven flow cytometry device of the present application;

FIG. 12 is a schematic structural diagram of the radiation force generating mechanism of the present application in one embodiment.

Detailed ways

The present application will be further described in detail below through specific embodiments in conjunction with the accompanying drawings.

Example 1:

As shown in FIG. 1 , the acoustic-driven flow cytometry detection device of the present application, an embodiment thereof, includes a cell manipulation module 10 , an imaging module 20 and an image processing module 30 . The cell manipulation module 10 is used to manipulate the cell particles in the sample solution, the imaging module 20 is used to perform fluorescence imaging on the stained cell particles, and the image processing module 30 is used to process and analyze the fluorescence images, count the cell particles and estimate the size of the cell particles . The cell manipulation module 10 may include a flow chamber and an ultrasonic radiation force generating system, and the flow chamber may be a microchamber for containing a sample solution containing cell particles. The ultrasonic radiation force generation system is used to generate acoustic radiation force on the cell particles, control the cell particles to arrange into parallel lines, realize multi-line focusing, suspend the cell particles, and drive the cell particles to be transported directionally to the detection area to achieve multi-channel parallel detection.

The imaging module 20 may include a fluorescence excitation source, an optical lens, and a highly sensitive fluorescence camera. The image processing module 30 may include a computer, a high-speed data acquisition card, hardware control software, and image acquisition and analysis processing software. The image processing module is used for processing and analyzing fluorescence images, counting cells and estimating cell size. The focus and transport of cells are mainly realized by the radiation force generated by the ultrasonic radiation force generation system.

In one embodiment, the ultrasonic radiation force generating system includes a radiation force generating mechanism, a signal generator and a power amplifier. After the electrical signal generated by the signal generator is amplified by the power amplifier, the radiation force generating mechanism is excited to generate ultrasonic waves, and then the radiation force is generated on the particles to realize the transportation and manipulation of the cells.

The flow chamber of the present application may include a substrate, PDMS sidewalls and a glass top cover, the PDMS sidewalls are bonded to the substrate, and the PDMS sidewalls are also bonded to the glass top cover. In one embodiment, the substrate may be made of quartz glass, plexiglass, or silicon.

In one embodiment, the radiation force generating mechanism may include an ultrasonic transducer and an artificial structure. The ultrasonic transducer is placed outside the flow chamber, and the artificial structure is placed in the flow chamber. The electric signal amplified by the power amplifier excites the ultrasonic transducer to generate ultrasonic waves and then generates radiation force on the particles. The artificial structure may specifically be an artificial periodic structure or an artificial aperiodic structure. As shown in FIG. 2 , the artificial periodic structure includes a substrate 11 and a plurality of protruding strips 12 arranged on the lower surface of the substrate 11 , and the protruding strips 12 are arranged in parallel and at equal intervals. Fig. 2 is a schematic diagram of an artificial periodic structure adopted in the acoustic radiation force generating system. t is the plate thickness, p is the period of the structure, w is the width of the grid, and h is the height of the grid. The material is stainless steel, and the parameters are t=20-100 μm, h=10-50 μm, w=20-100 μm, p=50-300 μm. Fig. 3 is the transmission spectrum of the artificial periodic structure shown in Fig. 2, the resonance frequency of which is 5.94 MHz.

In the ultrasonic radiation force generating system of the present application, the ultrasonic transducer is arranged outside the flow chamber, and the ultrasonic transducer does not coincide with the geometric center of the artificial periodic structure. In one embodiment, the ultrasonic transducer may be affixed to the outside of the flow chamber, in particular to the lower surface of the substrate. The ultrasound transducer may be a biased Gaussian beam sound source. The artificial structure modulates the sound field emitted by the ultrasonic transducer to generate a sound field with manipulation functions such as transport and arrangement, so as to realize the focusing and transport of cells.

Numerical simulation studies the acoustic radiation force of cells in the acoustic field obtained by the artificial periodic structure modulated Gaussian sound beam, and reveals the mechanism of directional transport of micro-nano particles in the artificial structure sound field. Figure 4 shows the distribution of the sound field modulated by the artificial periodic structure along the x direction. It can be seen that the sound pressure distribution obeys the Gaussian distribution. The dotted line part is the theoretical calculation value, and the solid line part is the experimental measurement value. As shown in Figure 5, cells are subjected to acoustic radiation forces in three directions of x, y, and z in the sound field of the artificial structure, and the acoustic radiation force Fx in the x direction causes the directional movement of the micro-nano particles in the direction of the strongest sound field to achieve transportation; The acoustic radiation force Fy in the y-direction causes the arrangement of micro-nano particles to achieve focusing, and its confinement effect on the particles limits the lateral movement range of the micro-nano particles, forming a virtual micro-channel; the acoustic radiation force Fz in the z-direction is responsible for Suspension and capture of micro and nano particles. The combined action of these three directional acoustic radiation forces ultimately leads to cellular transport and focusing.

Figure 6 shows the sound pressure field distribution and the directions of the radiation force components Fy and Fz when the artificial periodic structure resonates in the yz plane (the resonance frequency is 5.94 MHz). FIG. 7 is the distribution of the radiation force components Fy and Fz along the y direction when the artificial periodic structure is resonated in the yz plane (the resonance frequency is 5.94 MHz). It can be seen that in the equilibrium position shown by the circle, the radiation force component Fz is negative, that is, vertically downward, thus stably trapping cells on the surface of the structure.

Figure 8 shows the non-resonant sound pressure field (the driving frequency is 5.92 MHz) and the directions of the radiation force components Fy and Fz obtained by numerical simulation. Fig. 9 shows the sound pressure field (the driving frequency is 5.92MHz) and the spatial distribution of the radiation force components Fy and Fz along the y-direction obtained by numerical simulation when the sound pressure field is off-resonance. Figure 8 is a schematic diagram of the sound field distribution and force in the yz plane. It can be seen that the sound field shape at non-resonance is very different from the sound pressure field distribution at resonance in Figure 6. The positions shown by the circles are the equilibrium positions of the particles in the sound field. At this position, in the z direction, the vertically upward radiation force component Fz just cancels the effect of gravity, so that the particles are suspended; in the y direction, the sound radiation force component Fy = 0 in the y direction at this position, and the deviation from this position Fy is not zero, the direction is directed to this position, so this position is the equilibrium position of the particles in the y direction, and they are arranged one by one along the transport direction to achieve focusing.

Fig. 10 shows the spatial distribution of the radiation force components Fx and Fz along the transport direction x when the non-resonant (driving frequency is 5.92MHz) is calculated by numerical simulation. The position of x=0 is the center of the sound source, where the sound pressure is the highest. It can be seen that the radiation force component Fz is always positive, which means that the direction of the force is opposite to the direction of gravity, thus suspending the particles. The radiation force component Fx is zero at the center of the sound source (x=0), and is always positive at positions away from the center of the sound source. This means that the direction of the radiation force component Fx is directed towards the center of the sound source, so the radiation force component Fx will drive the directional transport of the particles towards the sound source.

Since the application uses the acoustic radiation force to manipulate the cell particles to achieve transport and focusing, there is no need for a complex pump system to drive the control fluid, nor to introduce sheath fluid; because the application uses the acoustic radiation force to arrange the cells in a virtual channel, there is no need to present There are micro flow channels used in the technology, so the problem of channel blockage is avoided; due to the acoustic radiation force can arrange multiple rows of cells, multi-channel parallel processing of multiple rows of focusing is realized; The flow chamber and other components have low cost and simple process, and can be replaced with new devices every time a new sample is measured, thus avoiding the problem of contamination of new samples by residues in the flow channel in the prior art. In conclusion, the present application provides a low-cost flow cytometry detection solution without microfluidic channel, without microfluidic pump, without sheath fluid, which can be discarded, can be processed in parallel.

Embodiment 2:

The second embodiment is a specific application example of the acoustic-driven flow cytometry detection device of the present application. Using C304 stainless steel, based on a standard chemical etching process, the artificial periodic structure shown in Figure 2 was prepared, and its parameters were t=30 μm, h=20 μm, w=50 μm, p=200 μm. The flow cell consists of a quartz glass substrate, PDMS (polydimethylsiloxane) walls and a glass top cover. The PDMS wall can be bonded to the base and cap. The ultrasonic transducer is a PZT4 piezoelectric ceramic sheet with a center frequency of 6MHz, which is bonded to the glass substrate through epoxy resin. The geometric center of the ultrasonic transducer does not coincide with the geometric center of the artificial periodic structure, that is, the ultrasonic transducer needs to be placed offset, the purpose is to generate a biased sound source, so that the cell particles deviated from the center of the sound source are affected as shown in Fig. The effect of the radiation force Fx shown, so that the directional transport to the sound source occurs. The control software controls the signal generator (AFG3102, Tektronix, Beaverton, OR, USA) to generate a Chirp signal with a frequency of 5.90-5.94 MHz, and after being amplified by a power amplifier (150A100B, Amplifier Research, Souderton, PA, USA), the piezoelectric ceramic is excited Sheet PZT4 produces ultrasonic waves. The ultrasonic excitation of the artificial periodic structure produces the local field shown in Fig. 8 on its surface, and produces the acoustic radiation force shown in Fig. 9-10 on the cell particles. When the cells are transported to the detection area, a high-pressure mercury lamp with a fluorescence excitation light source of 100W excites the stained cells to emit fluorescence, and a high-sensitivity fluorescence camera (QIMAGING optiMOS) records the fluorescence images and transmits the data to the computer. The image analysis processing software extracts the fluorescence intensity distribution of the image, and further calculates the size and number of cells.

Figure 11 is an image acquired using an acoustically driven flow cytometry system. The cells used in the experiment were MCF-7 tumor cells with a diameter of 15 μm. Cells were stained with calcein fluorescent dye and injected into the flow chamber. The radiation force generated by the ultrasonic radiation force generation system aligns and transports these cells to the detection area. When these cells reach the detection area, the fluorescent excitation light source excites the stained cells to emit green fluorescence, and the fluorescent image is recorded by a high-sensitivity fluorescence camera and transmitted to the computer via a high-speed acquisition card. The image analysis and processing software of the computer automatically extracts the fluorescence intensity curve, and calculates the size and number of cells according to the peak size and the number of peaks. Figure 11 extracts the fluorescence intensity curve of a single column of cells in the dashed box.

Embodiment three:

The difference between the third embodiment and the first embodiment is that the structure of the radiation force generating mechanism is different. As shown in Figure 12, the radiative force generating mechanism may include a plurality of transducers positioned outside the flow chamber and used to synthesize the sound field.

In one embodiment, the plurality of transducers include at least one ultrasonic transducer and interdigital transducers that appear in pairs and are arranged in parallel. The interdigital transducers are used to synthesize standing wave fields and align cells to achieve focusing. The energizer is used to generate a biased Gaussian beam for cell transport. There may be a pair of interdigital transducers or multiple teams. Figure 12 includes a pair of interdigital transducers, namely the first interdigital transducer 13 and the second interdigital transducer 14, in which the ultrasonic transducer The device 15 is the piezoelectric transducer PZT, and the 40 is the cell. The interdigital transducer 1 and the interdigital transducer 2 are used to synthesize the standing wave field to align the cells to achieve focusing, and the piezoelectric transducer PZT is used to generate a biased Gaussian beam to transport the cells.

The ultrasonic radiation force generating system may include multiple ultrasonic transducers, signal generators and power amplifiers. A portion of the ultrasound transducers were used to manipulate the cell alignment focus; the other portion of the transducers acted as a biased Gaussian beam sound source to drive particle transport. The sound field synthesized by multiple ultrasonic transducers emits sound waves to generate a sound field with manipulation functions such as transport and arrangement, so as to realize the focusing and transport of cells.

The above content is a further detailed description of the present application in conjunction with specific embodiments, and it cannot be considered that the specific implementation of the present application is limited to these descriptions. For those of ordinary skill in the technical field to which the present application pertains, some simple deductions or substitutions can also be made without departing from the concept of the present application.

Claims (10)

1. a kind of sound-driving flow cytometry detection device, including cell operational module, image-forming module and image processing module, institute Cell operational module is stated for manipulating to the cell granulations in sample solution, the image-forming module is used for staining cell Grain carries out fluorescence imaging, and described image processing module counts for processing and analysis of fluorescence image, to cell granulations and estimates thin Born of the same parents' granular size, which is characterized in that the cell operational module includes flow chamber and ultrasonic radiation force generating system, the flowing Room, for holding the sample solution containing cell granulations；The ultrasonic radiation force generating system is used for cell granulations generation sound Radiant force, manipulation cell particle are arranged in parallel lines, realize that multirow focuses, so that cell granulations is suspended, while driving cell granulations Directed transport to detection zone realizes multi-channel parallel detection.

2. sound-driving flow cytometry detection device as described in claim 1, which is characterized in that the ultrasonic radiation force occurs System includes radiant force generation mechanism, signal generator and power amplifier, and the electric signal that the signal generator generates is through institute After stating power amplifier amplification, excitation radiation power generation mechanism generates ultrasonic wave and and then generates radiant force to particle to realize pair Cell transporting and manipulating.

3. sound-driving flow cytometry detection device as claimed in claim 2, which is characterized in that the flow chamber includes base Bottom, PDMS side wall and glass roof, the PDMS side wall are bonded with the substrate and the glass roof respectively, the substrate by Quartz glass, organic glass or silicon are made.

4. sound-driving flow cytometry detection device as claimed in claim 3, which is characterized in that the radiant force generation mechanism Including ultrasonic transducer and it is placed in the indoor artificial structure of flowing, through the amplified electric signal of the power amplifier, excitation institute Ultrasonic transducer is stated to generate ultrasonic wave and and then generate radiant force to particle.

5. sound-driving flow cytometry detection device as claimed in claim 4, which is characterized in that the artificial structure includes people Work periodic structure or artificial aperiodic structure.

6. sound-driving flow cytometry detection device as claimed in claim 5, which is characterized in that the artificial cycle structure packet Substrate and multiple raised lines that the base lower surface is set are included, the tab parallel is arranged and is spaced equal.

7. sound-driving flow cytometry detection device as claimed in claim 4, which is characterized in that the artificial structure is not using Rust Steel material is made.

8. sound-driving flow cytometry detection device as claimed in claim 6, which is characterized in that the ultrasonic transducer setting Outside the flow chamber, and the ultrasonic transducer is not overlapped with the geometric center of the artificial cycle structure.

9. sound-driving flow cytometry detection device as claimed in claim 3, which is characterized in that the radiant force generation mechanism Including being placed in flowing outdoor use in multiple energy converters of synthesis sound field.

10. sound-driving flow cytometry detection device as claimed in claim 9, which is characterized in that the multiple energy converter packet At least one ultrasonic transducer and in pairs appearance and interdigital transducer disposed in parallel are included, the interdigital transducer is stayed for synthesizing Wave field arranging cells, which are realized, to be focused, and the ultrasonic transducer transports cell for generating biasing Gaussian beam.