SELF-POWERED TRIBOELECTRIC SENSOR BASED ON DIRECT CHARGE TRANSFER BETWEEN LIQUID-TREATED SOLID FOAM AND METAL CONTACTS

Abstract

In recent years, there has been a growing demand for self-powered sensors that can work independently, without external power sources, particularly in situations where conventional power options like batteries aren’t feasible. Since 2012, the triboelectric nanogenerator (TENG) has shown promise in harvesting mechanical energy and sensing. However, traditional TENGs produce alternating current, so a conversion to direct current (DC) is necessary for powering electronic devices that need DC power. This thesis introduces a new method for straightforward converting mechanical energy into DC power. It involves a simple setup with two metal contacts that gather DC power created when a liquid-treated solid foam made of water and cellulose (referred to as the “active layer”) is slid. The energy conversion relies on the combination of the triboelectric effect and direct charge transfer between the metal contacts, which is different from traditional TENGs. The active layer plays an important role in effectively separating and transferring the charge generated by friction energy through an internal conductive path formed by a hydrogen-bonded network of water molecules. C-TEG generates a current density of 0.75 A/m2 and a voltage of around 0.5 V with DC characteristics. It also exhibits high accuracy in measuring the ion concentration in aqueous solutions. This technology has led to the development of the cellulose-based triboelectric self-powered multifunctional sensor (C-TSMS), which combines energy harvesting and sensing capabilities into a unified device. C-TSMS shows excellent linearity and precision in responding to various stimuli like pressures, sliding velocities, water absorption, and ion concentrations (R2 > 0.99). For self-powered operation, the voltage output can be further boosted by connecting multiple C-TSMSs and then successfully used to directly power functional electronics. Furthermore, a new structural design improves C-TEG’s performance by changing the electrode configuration, shifting from a freestanding mode to a lateral sliding mode. This modification results in a remarkable current density of 3.57 A/m2 and effective electric power harvesting (up to 0.174 W/m2). In summary, these findings highlight the potential of this approach for capturing low-frequency mechanical energy from the environment across a range of applications, especially in the realm of self-powered sensors.

This research makes a significant contribution to advancing energy harvesting technology by providing valuable insights, innovative methodologies, and practical demonstrations that enhance the capabilities of current systems. It investigates the potential of cellulose foam as a functional material, highlighting its distinctive mechanical attributes and compatibility with the triboelectric effect. This emphasis showcases its promise for applications in highly sensitive multifunctional sensing across various domains, including pressure sensing, motion detection, humidity assessment, and ion concentration detection.