Piezoresistive Sensing Platform for High-Throughput Single Platelet Nanomechanics

异常凝血和出血是心脏病、中风和癌症等许多疾病的病因或致命并发症。在血栓形成过程中，生化活化的血小板与生长的纤维蛋白聚合物网络相互作用，并与纤维蛋白支架发生收缩。今天，很少有工具可以预测一个人何时可能会出现异常凝血或出血，而且几乎所有这些工具都依赖于感知与凝块形成或破裂相关的生化物质。然而，新的研究表明，血小板名义上施加的物理力量的变化与出血有关。因此，该项目的最终目标不是试图检测与凝血相关的微量生化物质，而是检查血小板力以预测异常出血和凝血。细胞的物理强度可能与出血和凝血直接相关，因此代表了一种潜在的“破坏性”生物物理测试范式，可应用于许多其他疾病。虽然有希望，但这种新方法需要分析大量的血小板来获得临床相关数据并预测出血和凝血障碍。使用今天的技术，主要是利用基于显微镜的光学技术，这仍然需要太多的时间才能在临床中发挥作用。为了克服光学技术测量血小板力的局限性，本提案寻求探索非光学转导机制，以创建能够分析大量单个血小板的快速，高通量平台。更具体地说，该项目的目标是开发用于单血小板高通量机械测试的压阻传感平台。使用压阻式传感器进行力传感，所提出的平台将克服所有现有技术的高通量单细胞力分析的关键瓶颈，即它们对光学成像的依赖。这两种传感平台基于微点和纳米柱阵列，分别模拟了用于细胞力测量的两种最常见的光学平台——牵引力显微镜和微制造柱阵列探测器。因此，血小板对一对微点施加的收缩力可以用亚微米应变计测量，而血小板收缩引起的纳米柱偏转可以通过嵌入衬底的应力敏感金属氧化物半导体场效应晶体管（MOSFET）来感知。在传感系统方面，智能优势在于设计和制造具有纳米牛顿力分辨率的超小尺寸压阻式力传感器阵列，目标是微点/柱对的间距小于15µm。

Abnormal clotting and bleeding are the cause, or a lethal complication, of many diseases including heart disease, stroke, and cancer. During the formation of blood clots, biochemically activated platelets interact with growing networks of fibrin polymers and contract against this fibrin scaffold. Today, few tools exist to predict when a person may experience abnormal clotting or bleeding, and nearly all of these tools rely on sensing biochemicals associated with clot formation or breakup. However, new research has shown that changes to the physical forces nominally applied by platelets are associated with bleeding. Rather than attempting to sense trace amounts of biochemicals associated with clotting, the ultimate goal of this project is, thus, to examine platelet forces to predict abnormal bleeding and clotting. The physical strength of a cell may be directly linked to bleeding and clotting, thus representing a potentially "disruptive" paradigm of biophysical testing that could be applied to many other diseases. While promising, this novel approach requires assaying a large population of platelets to gain clinically relevant data and predict bleeding and clotting disorders. Using today's technologies, which are mostly utilizing microscopy-based optical techniques, this still requires too much time to be useful in the clinic. To overcome the limitations of optical techniques to measure platelet forces, this proposal seeks to explore non-optical transduction mechanisms to create a rapid, high-throughput platform capable of assaying large numbers of individual platelets. More specifically, the goal of this project is to develop piezoresistive sensing platforms for high-throughput mechanical testing of single blood platelets. Using piezoresistive transducers for force sensing, the proposed platforms will overcome the key bottleneck to high-throughput single-cell force analysis with all existing techniques, namely their reliance on optical imaging. The two proposed sensing platforms are based on arrays of microdots and nanopillars and mimic the two most common optical platforms for cell force measurements, traction force microscopy and microfabricated post array detectors, respectively. Thereby, the contraction force exerted by a blood platelet on a pair of microdots is measured with underlying sub-micrometer strain gauges, while the platelet-contraction-induced deflection of nanopillars is sensed by stress-sensitive metal-oxide-semiconductor field effect transistors (MOSFET) embedded into the underlying substrate. On the sensing system side, the intellectual merit lies in the design and fabrication of large arrays of piezoresistive force sensors with nano-Newton force resolution in an ultra-small form factor, targeting a pitch for the microdot/pillar pairs of less than 15µm.