Microfluidic Cell Sorting and Manipulation Based on Bulk Acoustic Waves

南加州大学（USC）获得了一项奖项，以推进基于聚焦体声波的换能器技术，用于微流体系统中的细胞分选和操作。具体的生物应用将是基于细胞大小或机械刚度的细胞分选，将基因微注射到活细胞中，以及在微流体通道中选择性地收集含有细胞的液滴。由于换能器基于体声波，该技术提供了镊子活细胞，没有力限制，热量或透明介质的要求。此外，由于换能器仅将声能聚焦在非常小的点上，并且能够通过中间固体传递声能，因此它可以应用于各种微流控平台，用于管理细胞、液体、颗粒和蛋白质。换能器对捕获力位置/方向的电气可控性，加上换能器形成阵列的适应性，允许以高通量创建复杂的生化分析和/或生物医学治疗。因此，换能器在三维（3D）空间中捕获和按需操作活细胞和/或颗粒（直径数十-数百微米）的前所未有的能力将为细胞研究、基因转染、并并和操作开辟许多新的可能性。在研究期间的第2年和第3年，这些传感器和功率放大器将交付给四个选定的生物实验室，以便实验室可以使用它们进行分选、基因传递或任何其他生物实验。研究结果将被纳入首席研究员的微机电系统（MEMS）教科书的第二版，题为“微机电系统基础”，以及在南加州大学的微机电系统课程。拓展活动将包括为本科生和高中生提供研究经验，他们将对涉及细胞和微粒的实验感到兴奋。此外，来自代表性不足群体的学生将被积极招募参加拟议的研究。换能器将基于多焦点菲涅耳换能器（MFT），能够根据需要在3D空间中捕获和移动微粒。特异性靶向生物捕获和移动的应用将包括基因显微注射（通过声孔）和脂质介导的基因传递。还将开发基于mft的微流控通道细胞分选以及微流控通道中含细胞液滴的形成和收集。一种先进版本的MFT具有两个重叠的圆形电极，已被证明可以使超声波沿垂直轴到达狭窄的区域，并具有建设性的波干涉，从而产生具有长聚焦深度的窄贝塞尔光束样焦区。这个过程也会产生瓶束和准艾里光束，其中存在向内部区域的辐射力，因此可以捕获多个粒子。这个先进的版本将与各种其他版本的MFT一起开发，优化和测试特定的生物仪器。将开发三维空间中镊子位置的电气可控性，以便捕获的细胞可以：(1)从一个位置移动到另一个位置，(2)拉伸或压缩，(3)与其他细胞或含有基因的脂质体接触，所有这些都是在电子命令信号下进行的，而无需移动换能器。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

An award is made to University of Southern California (USC) to advance the transducer technology based on focused bulk acoustic waves for cell sorting and manipulation in microfluidic systems. Specifically targeted biological applications will be on cell sorting based on cell’s size or mechanical stiffness, microinjection of genes into living cells, and selective collection of cell-containing droplets in a microfluidic channel. As the transducers are based on bulk acoustic waves, the technology offers tweezing live cells without force limitation, heat, or requirement of transparent media. Moreover, since the transducer focuses acoustic energy only on a very small spot and is capable of delivering acoustic energy through an intermediate solid, it can be applied to various microfluidic platforms for management of cells, liquids, particles and proteins. The transducer’s electrical controllability on the location/direction of the trapping force, combined with amenability of the transducers being formed into an array, allows the creation of complex biochemical assays and/or biomedical treatments at high throughput. Thus, the transducer’s unprecedented capability of capture and on-demand manipulation of living cells and/or particles (tens - hundreds of microns in diameter) in three dimensional (3D) space will open up many new possibilities in cell study, gene transfection, juxtaposition and manipulation. Sets of the transducers and power amplifiers will be delivered to four selected biological labs during the years 2 and 3 of the research period so that the labs may use them for sorting, gene delivery or any other biological experiments in their labs. The results of the research will be incorporated into the second edition of the principal investigator’s textbook on microelectromechanical systems (MEMS), entitled “Fundamentals of MEMS,” as well as in the MEMS curriculum at USC. Outreach activities will include research experience for undergraduate and high school students who will be excited with the experiments involving cells and microparticles. Also, students from underrepresented groups will be actively recruited for the proposed research.The transducers will be based on Multi-foci Fresnel Transducer (MFT) capable of capturing and moving microparticles in 3D space on demand. Specifically targeted biological applications of the capture and move will include gene microinjection (through sonoporation) and lipid-mediated gene delivery. Also developed will be MFT-based cell sorting in microfluidic channels as well as formation and collection of cell-containing droplets in a microfluidic channel. An advanced version of MFT having two overlapping circular electrodes has been shown to make the ultrasonic waves arrive at a narrow region along the vertical axis with constructive wave interference to create a narrow Bessel-beam-like focal zone with long depth-of-focus. This process also produces bottle beams and quasi-Airy beams where radiation force toward the inner region exists and thus, multiple particles can be trapped. This advanced version along with various other versions of MFT will be developed, optimized and tested for the specific biological instrumentations. Electrical controllability of the tweezing location in 3D space will be developed so that the captured cells may be: (1) moved from one location to another, (2) stretched or compressed, (3) brought into contact with other cells or gene-containing liposomes, all upon electrical command signal without having to move the transducers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.