Wearable devices have the potential to transform multiple facets of human life, including healthcare, activity monitoring, and interaction with computers. However, a number of technical and adaptation challenges hinder the widespread and daily usage of wearable devices. Recent research efforts have focused on identifying these challenges and solving them such that the potential of wearable devices can be realized. This monograph starts with a survey of the recent literature on the challenges faced by wearable devices. Then, it discusses potential solutions to each of the challenges. We start with the primary application areas that provide value to the users of wearable devices. We then present recent work on the design of physically flexible and bendable devices that aim to improve user comfort. We also discuss state-of-the-art energy harvesting and security solutions that can improve user compliance of wearable devices. Overall, this monograph aims to serve as a comprehensive resource for challenges and solutions towards self-powered wearable devices for health and activity monitoring.

The integrated circuit (IC) manufacturing process involves many players, from chip/board design and fabrication to firmware design and installation. In today’s global supply chain, any of these steps are prone to interference from rogue players, creating a security risk. Therefore, manufactured devices need to be verified to perform only their intended operations since it is not economically feasible to control the supply chain and use only trusted facilities. This paper presents a detection technique for malicious activity that can stem from hardware or firmware Trojans. The proposed technique relies on (i) repetitious side-channel sample collection of the active device, (ii) time-domain stitching, and (iii) frequency domain analysis. Since finding a trusted sample is generally impractical, the proposed technique is based on self-referencing to remove the effects of environmental or device-to-device variation in the frequency domain. We first observe that the power spectrum of the Trojan activity is confined to a low-frequency band. Then, we exploit this fact to achieve self-referencing using signal detection theory. The proposed technique’s effectiveness is demonstrated through experiments on a wearable electronics prototype and system-on-chip (SoC) under a variety of practical scenarios. Experimental results show the proposed detection technique enables a high overall detection coverage for malicious activities of varying types with 0.8 s monitoring time overhead, which is negligible.

Biological and chemical sensor systems have many potentially transformative applications including health care, environmental monitoring, and biological or chemical threat detection. A major impediment in the widespread use of low-cost sensors, such as ChemFETs (Chemically sensitive Field-Effect Transistors), is the degradation in accuracy due to drift which occurs immediately after deployment. This paper presents a fully automated soft-calibration technique that extends the lifetime of sensors by compensating drift. The proposed methodology is applied to pH sensors, which can be manufactured for less than 10 cents. Experimental results show we can achieve very accurate results even if the sensor output has drifted by more than 600%. The proposed technique has been shown to extend the usable time of the ISFET sensor from mere minutes to 8 hours.