Testing Wearable Devices without the Need for Human Subjects: In Vitro Test Platform for Optically-based Sensors
John P. Hanks, Casey W. Pirnstill and Gerard L. Coté
Center for Remote Health Technologies & Systems
Texas A&M University
Many wearable smart bands, watches, and other devices use optically-based sensors to measure a variety of fitness and health related measurements such as heart rate, pulse oximetry, and blood pressure. According to an industry market research firm CCInsights [1], 22 million wearable smart devices were shipped in 2014, and with the release of the Apple Smart Watch, IDC[2] predicts more than 45 million smart devices will ship in 2015. Furthermore, Gartner[3] predicts that more than 40% of smart phones will include biometric measurements by 2016. The primary optical sensor on most of the current devices is a reflectance, photoplehysmography (PPG) based device used for measuring heart rate and heart rate variability (HRV). Although many improvements have been made with these devices, a common problem is their susceptibility to motion artifact during physical activity and the low signal output because of variances in skin tone. In this research, we report on the development of an in vitro test and validation platform that simulates the optical properties of varying skin tones, tissue and blood and incorporates robotic motion protocols that mimic running, jumping, sitting, and waving. The system also controls for different blood flow rates and amplitudes. With this test platform developers can systematically evaluate the performance of current commercially available wearable devices on the benchtop. The same platform can be used to test and validate new semiconductor and photonics components, and new biometric algorithms— without using human subjects. This test platform removes the inherent challenges in working with human subjects in the early stages of design. Semiconductor companies can benefit by reducing the number of design iterations and cost before final product release. The platform technology will be discussed and preliminary results presented showing the utility of the instrument across several watch-based PPG platforms.
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