Distributed Microsensor Packaging Based on Self-Assembly after Sensing

在该提议中，提出了一种操作后封装过程，其中太小而不能包括数据传输电子器件的分布式微传感器可以在它们执行其感测操作之后使用自组装进行封装和读取。当今使用的许多系统中，流体通过非常小的通道流动。实例包括流式细胞术、燃料喷射和化学处理。在这样的系统中，关于流的物理状态的良好信息可能难以获得，因为设置在流中的传感器可能难以定位，并且可能干扰它们应该测量的过程。一个可能的解决方案是使用实际上随流动而移动的移动的微传感器来收集数据。这是非常有吸引力的，因为感测可以连续地和原位地执行，但是它具有一些基本的技术困难，因为由于尺寸和成本限制，电源和数据传输电子器件将难以包括在内。此外，如果使用非常大量的传感器，则协调所有传感器的传输协议将是不切实际的。PI建议通过使用流体自组装（FSA）来解决这些问题，以便在设备感测后从设备中封装和读出信息。由于传感操作通常消耗的功率比数据传输操作少得多，来自环境的环境能量（如光或RF）可用于驱动传感器，并且所有用于数据传输的接口都将由自组装过程提供。工程目标之一是开发一种流体测试装置，以研究术后包装。功率传输到微传感器将重点考虑使用环境光，激光和RF功率。由于这些电源可能是间歇性的，因此非易失性数据存储极其重要。非易失性存储器技术，写用非常少的权力，使用隧道进程将被审查。与自组装微传感器的电子接口可能是最关键的工程问题。金属键合，微机电开关，和电容耦合被认为是。微机电开关被挑选出来作为特别通用的，因为它们不需要在微传感器上的特殊电路，并且可以在读取数据后将微传感器释放回流中。科学目标包括研究自组装捕获过程，即自由微传感器如何移动到组装现场的影响范围内。还将进行流体自组装过程的静电“微调”研究，其中使用电容耦合来引导组装的最后阶段，可以消除微米级的未对准。还将对流中的器械寿命进行研究。这些将试图确定是否可以修改流体动力学或使用保护涂层来最大限度地减少对反复循环通过流体系统的设备的机械损坏。该计划的设计考虑到了教育目标。某些项目，如生命周期研究和自组装捕获研究的一部分，已被确定为短期项目，适合引入本科生的研究。其中一些工作可以作为明尼苏达大学本科生研究机会计划（UROP）或本科生研究经验（REU）计划的一部分，为代表性不足的学生或来自小型大学的学生进行。无论是研究生和本科水平的工作是非常多学科的，让学生探索物理，化学和工程的实验以及理论方面。最后，该项目的技术影响是广泛的，在医学，遥感和工业过程控制等方面具有潜在的应用。这个项目，因为它的理念是只包括那些真正必要的功能在微型设备上，然后包装其余的以后，也可能是一个长期追求的目标，创造智能微型或纳米设备的第一步只有简单的初始功能，但有可能自组织新的功能，以响应他们的环境。

In this proposal, a post-operation packaging process is proposed where distributed microsensors that are too small to include data transmission electronics can be packaged and read using self-assembly after they have performed their sensing operations. There are many systems in use today where fluids move through extremely small channels. Examples include flow cytometry, fuel injection, and chemical processing. Good information about the physical state of the flow in such systems can be difficult to obtain because sensors set into the flow can be difficult to position and may interfere with the very processes that they are supposed to measure. One possible solution would be to collect data using mobile microsensors that actually travel with the flow. This is extremely appealing because sensing could be performed continuously and in-situ, but it has some basic technical difficulties since power supplies and data transmission electronics would be difficult to include due to size and cost restrictions. In addition, if an extremely large number of sensors were used, coordinating transmission protocols for all of them would be impractical. The PI proposes to solve these problems by using fluidic self-assembly (FSA) to package and read-out information from the devices after they have sensed. Since sensing operations typically consume much less power than data transmission operations, ambient energy from the environment such as light or RF could be used to drive the sensors and all interfacing for data transfer would be provided by the self-assembly process.The program has both practical engineering and fundamental scientific goals. Among the engineering goals is the development of a fluid test apparatus to investigate post-operation packaging. Power transfer to microsensors will be examined with emphasis given to the use of ambient light, laser, and RF power. Since these power sources may be intermittent, nonvolatile data storage is extremely important. Nonvolatile memory technologies that write with very little power using tunnel processes will be examined. Electronic interfacing to the self-assembled microsensors is perhaps the most critical engineering issue. Metallic bonding, micro-electro-mechanical switching, and capacitive coupling are considered. Micro-electro-mechanical switches are singled out as particularly versatile because they require no special circuitry on the microsensor and can release microsensors back into the flow after their data has been read. Scientific goals include studying the self-assembly capture process, that is, how free microsensors move into the sphere of influence of the assembly site. A study of electrostatic "fine-tuning" of the fluidic self-assembly process will also be performed, where micron-scale misalignments might be eliminated using capacitive coupling to guide the final stage of assembly. Studies will also be performed on device lifetimes in a flow. These will attempt to ascertain if flow dynamics can be modified or protective coatings used to minimize mechanical damage to devices that have circulated repeatedly through a flow system.The program has been designed with educational objectives in mind. Certain projects, such as the lifetime studies and parts of the self-assembly capture studies have been identified as shorter-term projects suitable for introducing undergraduates to research. Some of this work could be performed as part of the University of Minnesota's Undergraduate Research Opportunities Program (UROP) or Research Experience for Undergraduates (REU) program for underrepresented students or those from small universities. Both the graduate and undergraduate level work is extremely multidisciplinary, allowing students to explore experimental as well as theoretical aspects of physics, chemistry and engineering. Finally, the technological impact of the project is broad, with potential applications in medicine, remote sensing, and industrial process control, among others. This project, since its philosophy is to include only those functions that are truly necessary on a microdevice and then package the rest later, may also be a first step in a long sought goal to create smart micro- or nanodevices with only simple initial capabilities, but the potential to self-organize new functions in response to their environment.