Digital Fabrication and Integration of a Flexible Wireless Sensing Device

In this paper, we combine high functionality c-Si CMOS and digitally printed components and interconnects to create an mostly printed integrated electronic system on a flexible substrate that can read and process multiple discrete sensors. Our approach is to create an integrated platform for the fabrication of mechanically flexible sensor tags that can be powered and interrogated wirelessly, precluding the need of a separate on-board power source. The high level system design is aimed at minimizing the number of non-printed components and reducing power consumption to enable energy harvesting from the RF field. Digital fabrication of these systems requires a range of materials, feature sizes, and electrical characteristics. In order to integrate the various printed components on a single substrate, we developed an integrated printer to accommodate a range of inks for printing the antenna, different types of sensors, chip interconnects, and wiring. For chip attachment to the flexible substrate, a method of integrating the die within the thickness of the substrate was developed. With proper system design and fabrication, a complete integrated tag for wireless sensing of temperature, strain, and touch was demonstrated. Our approach facilitates customization to a wide variety of sensors and user interfaces suitable for a broad range of applications including remote monitoring of health, structures, and the environment.