Advanced Microsystems through alternative microfabrication processes

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A World Economic Forum report on the future of manufacturing emphasized the need for flexible, rapid and low cost manufacturing. The project proposes a framework for the next generation microsystems aligned with this vision, supported by advances in three supporting pillars: manufacturing technology, device level innovations and a mostly-digital system architecture, easy to adapt and reconfigure. The microsystems of the future will consist of the hybrid integration on flexible or rigid substrates of microtransducers (arrays or clusters), a thin interfacing analog layer and advanced digital signal processing algorithms implemented on low-power off-the shelf silicon dies. The integration of printed antenna will also add the wireless interconnectivity in complex IoT structures, where the processing power can be delegated to the cloud. The low-cost, rapid manufacturing pillar relies on the robustness of photo-polymerization process of materials like SU-8, even when mixed with particles/molecules that modifies its physico-chemical properties. Functionalized SU-8 thin layers can be patterned by high resolution maskless lithography, so that they can be used to define (electrical and optical) interconnects, passive components, and microtransducers, from chemical sensors to moving MEMS structures. The technology will allow not only a high-density hybrid integration on flexible substrates with off-the-shelf dies, but also a die level integration (thin polymer sensor layer on the top of a Si die). To enable further scalability, modern device level techniques will exploit the electromechanical coupling to enhance the sensitivity at microscale: operation on the stability border, parametric amplification and mode localization effects in weakly-coupled resonators. The third pillar addresses the system-level architecture, where the desire to minimize the analog electronic interface leads to mostly digital closed-loop systems, based on sliding mode control. Three target applications will validate the vision: (1) an advanced inertial measurement unit (IMU) for inertial navigation, (2) an ultrasound imaging transducer based on polymer CMUT arrays and (3) a resonant polymer cantilever array with embedded microfluidic channels for fluid analysis. The IMU will validate the polymer-based technology for in-plane movable MEMS structures, and will use high-sensitivity accelerometers operated on their stability border through digital sliding mode control, while the gyroscope sensitivity will be enhanced through parametric amplification. The CMUT array will validate the out-of-plane electrical actuation and hermetic sealing. The weakly-coupled cantilevers with shaped microfluidic channels for fluid analysis will exploit mode localization effects to increase the sensitivity of the sensors with orders of magnitude compared to the common frequency shift sensing technique.