An Inkjet-Printed Paper-Based Flexible Sensor for Pressure Mapping Applications

Biometric observation using portable and wearable sensors is transforming health monitoring since patients can now have their conditions frequently checked outside the hospital setting. However, modern biosensors mostly use the standard printed circuit board substrate, which is physically incompatible with irregular-surface applications. The need for a flexible, low-cost and high-resolution monitoring device for observing elderly patient mobility out of hospital settings is the motivation driving this research. The following paper is a characterization of an experimental inkjet-printed sensor that circumvents the problem of rigidity by using a highly flexible substrate while also benefiting from low fabrication costs, low power usage, and environmental friendliness. The sensor is a 4 × 4 grid of Aluminum-doped Zinc Oxide nodes inkjet-printed on paper-based substrates. The tests performed show nodes are capable of responding to applied pressures of over 540 PSI. Notably, they exhibit sensitivity to heat and humidity without shielding measures, making it more useful for physical therapy. Power usage of the device is shown to be as low as 5 μW. Silver nanoparticle ink was chosen as electrical routing between the Zinc Oxide and data collection scheme. The analog signal is connected through ELVIS II+ analog pins, where a MATLAB script retrieves and stores the data for visual analysis. The cost of printing a single pressure node of this sensor is estimated to be $0.01. These conditions make it a monetarily attractive pressure sensing and mapping option for human impact monitoring applications.