Thermally-induced ion transport is important in thermal energy harvesting systems, wearable electronics and internet-of-things (IoT) technologies, and biotechnology. In thermal energy harvesting systems, this is a novel method that thermal energy can be transferred to electrical energy and stored in capacitors. In the wearable electronics and IoT technologies, advanced electronics need to be designed as more efficient and lower energy cost so that it can be powered by human body heat continuously. In biotechnology, controlling ion transport for desired reactions without external electrical energy input or only with a thermal input signal could facilitate or prevent particular ion engagement, which could be used for selective reactions or sensing. Ion transport behaviors under low-grade temperature gradients offer an opportunity to power portable electronics by body heat, because such ionic conductors generate high voltage with low-grade temperature gradients. Based on the mechanism of ion transport, materials with higher energy harvesting efficiency and higher thermopower have been designed and studied. In the past, the ion transport mechanism driven by thermal gradients in solid-state ionic conductors was barely studied, and the energy harvest efficiency was still low. The knowledge gained through this study about thermally-induced transport of ions and plasticizers can be utilized to establish new concepts and applications including energy harvesting/storage systems for wearable and portable electronics and beyond.

The ultimate goal of this project is to develop a novel simultaneous energy harvesting and storage system that utilizes typically wasted low-grade heat such as human body heat so that wearable and portable electronics can be powered without electrical charging from an external power outlet. This project investigates the key mechanisms for controlling ion transport under temperature gradients so as to simultaneously harvest and store electrical energy. The essence of this study is to understand how ions transport under temperature gradients, which has broader impacts on other fields for controlling reactions and flow directions. Understanding the key mechanisms in remarkably increasing thermopower is directly tied to the generated voltage to a level that actual wearable electronics can be operated. In particular, this project investigates plasticizer-dependent thermally-induced ion transport in solid-state ionic conductors. The plasticizer not only loosens the mobile ions from the counter ions tethered to the long backbone of the polymer, but also significantly affects ion transport under temperature gradients. Nevertheless these aspects have barely been studied and understood in the past. This project has mainly studied the thermal diffusion direction of ions and plasticizers, the role of plasticizers in promoting the thermal diffusion of ions, and the capacitance effect from the plasticizers. Based on the knowledge gained through the fundamental studies, optimally designed thermally chargeable supercapacitors have been developed and tested.

This project has provided students with the training on studying ion transport under temperature gradients, synthesizing polyelectrolyte composites, learning thermal and electrical property measurements, studying the mechanism about the Soret effect of ions as well as the basic principles of thermal transport and energy storage. Students improve their ability of writing and presenting scientific research outcomes. The research outcomes were integrated into undergraduate and graduate classes to enrich class contents with contemporary research outcomes. This project also substantiated a thermo-hydro-electrochemical conversion concept by powering electronic devices, including a fever detector that can be distributed to many unspecified people in public places at a low price. The hydro-electrochemical cell provides a new approach to utilizing water to generate electricity by hydro-electrochemical effects. This new energy conversion approach can contribute to the development of green energy and low-cost energy harvesting. In particular, a body temperature sensor was powered by a cheap, disposable, and reliable energy harvester, and this technology was utilized to detect fever for identifying the health condition like COVID-19. Also, with advances in wearables and internet-of-things (IoT) technologies, this thermal energy to electrical energy conversion has a great potential for sustainable power supply. The results have been disseminated through presentations in conferences and seminars and journal paper.

Last Modified: 07/29/2022
Modified by: Choongho Yu