Development of the Adapter Board System: a Control Hub for the Nanowell Sensor-Based Smart Bandage to Monitor Immune Dynamics in Wounds

Abstract

Because of the integral nature that they play in signaling cascades of the immune system, cytokines have emerged as analytes of interest for sensing systems, like the Nanowell Sensor platform, to provide information on healing and infection progression in wounds. Despite their sensitivity, Nanowell Sensors are limited from wide-scale adoption as a medical device due to their reliance on large, expensive bench-top instruments. A solution to this challenge is the creation of a "Smart Bandage" system that consists of Nanowell Sensors to measure the impedance of wound samples, a Direct Conversion chip that extracts impedance change information from the output signal of the sensors, and an Adapter Board to provide power, control, and digitization for the entire system. The purpose of this project was to design the Adapter Board, serving as the primary control hub for the Smart Bandage medical device that would provide continuous monitoring of wound healing progression. The Adapter Board was first designed and fabricated as a rigid PCB that hosted various I/O, power management, and processing sub-systems in order to provide digitization for low-frequency input. A controlling FPGA architecture was then developed to implement SPI communication in order to perform single-ended one-shot and continuous signal digitization with a ΔΣ ADC. One-shot DC analog-to-digital conversion yielded an average percent error of 4.4696% ± 0.04111% and continuous DC conversion yielded an average percent error of 4.4313% ± 0.0007%, confirming both the accuracy and precision of the system. The device also showed the ability to reconstruct low frequency AC sinusoids and ramps across multiple oversampling ratios. The development and characterization of this board marks a significant step toward the creation of "Smart Bandages" to provide continuous feedback on the state of wounds in patients via cytokine monitoring. 3