System with Integrated Inhalation-Driven Triboelectric Nanogenerator for Monitoring User Respiration and Detecting Chemical Warfare Agents

With the advent of the Internet of Things (IoT) era, various sensors and small/portable electronics are being installed or embedded in physical objects, machinery, and equipment to detect certain events or changes. The increased integration of such sensors in daily life activities poses challenges in terms of continuously supplying power to each sensor and managing the power requirements because the batteries must be appropriately replaced or recharged. Furthermore, external batteries are associated with several limitations such as a large system weight, space occupation, and environmental pollution. To address these problems, several researchers have explored sustainable and renewable future energy sources that can help operate small/portable electronics or function as self-powered sensors. Considerable research has been performed on mechanical energy harvesting devices such as piezoelectric, electromagnetic, and triboelectric generators, which produce electrical energy from mechanical movement without environmental constraints. Triboelectric nanogenerators (TENGs), which are based on the principles of triboelectric effect and electrostatic induction, have attracted research interest owing to their high energy efficiency, compatibility with easily available materials, and low cost. However, most of the existing TENGs generate a low current output (~μA) and high voltage output (~V) owing to their high internal impedance. Recently, several researchers attempted to develop TENGs with a high current output (~mA) by incorporating novel structures, additional electrical layers or external circuits. However, such TENGs require a large and automatic mechanical input for continuous electrical output generation, which limits its potential as a power source for small electronics in everyday life.<br/>Moreover, since self-powered sensors are widely used in emergency situations (fire, chemical gas exposure accident, etc.), immediate reaction via continuous sensing is very important. Accordingly, respiration, which is a typical example of natural / continuous mechanical input source, has been utilized to operate TENGs. Film-flutter TENGs are representative respiration-driven TENGs and can produce a continuous electrical output from an extremely small respiration input owing to the low weight of the film and exploitation of the flutter phenomenon. However, the existing film-flutter TENGs exhibit a lower current output (nA–μA) and voltage output (mV–V) than other types of TENGs, owing to the influence of the irregular contact behavior and low contact force on the output. This limitation must be addressed for TENGs to be used as portable power sources. Specifically, TENGs that can derive a high current output (~mA) from a small respiration input must be established.<br/>Considering these aspects, in this study, a novel inhalation-driven TENG (ID-TENG) with an amplified current output was developed for gas-mask-integrated self-powered multifunctional system. The mechanical structure of the ID-TENG was optimized by comparing the root-mean-square (RMS) voltage output in parametric experiments. The proposed ID-TENG is expected to function as a gas mask-integrated self-powered multifunctional system 1) auxiliary power source and 2) self-powered sensor. Specifically, the ID-TENG is expected to function as a self-powered user-position-indicating light. The stored energy of the ID-TENG can likely power a commercial Bluetooth tracker and wirelessly transmit the user location data. Moreover, the ID-TENG can potentially be used as a hybrid sensing system to examine the user respiration state and detect chemical warfare agents (GB, DMMP etc.) through the output waveforms.