11/07/2025
By Danielle Fretwell

The Francis College of Engineering, Department of Chemical Engineering, invites you to attend a Doctoral Dissertation Proposal defense by Cuilei Li on: "Fabrication and System-Level Integration of Highly Flexible and Wearable Thermoelectric-based Thermal Management System."

Candidate Name: Cuilei Li
Degree: Doctoral
Defense Date: Thursday, November 13, 2025
Time: 10 a.m. - noon
Location: ETIC 445

Committee:

  • Advisor: Zhiyong Gu, Professor/Chair, Department of Chemical Engineering, UMass Lowell
  • Nese Orbey, Associate Professor/Associate Chair, Department of Chemical Engineering, UMass Lowell
  • Ramaswamy Nagarajan, Distinguished Professor/Co-Director of HEROES, Plastics Engineering Department, UMass Lowell
  • Edward S Fratto, Post-Doc, U.S. Army Combat Capabilities Development Command (DEVCOM) Soldier Center

Abstract:
Wearable thermoelectric devices (TEDs) have shown great promise for localized personal cooling, offering silent operation, compactness, and precise thermal control without moving parts. However, challenges remain in improving energy efficiency, flexibility, durability, and real-world integration. This project develops an advanced flexible TED system by integrating Bi₂Te₃-based thermoelectric pillars with stretchable Ecoflex rubber and novel multi-directional copper electrode pattern that ensures highly flexibility without compromising performance. To maintain a stable temperature gradient, the device integrates a soft, conformable heatsink composed of AlN/Ecoflex silicone rubber, flexible copper foam, and phase-change materials (PCMs) to enable both effective heats spreading and dissipating and transient thermal buffering. In contrast to conventional fixed-current testing methods, we implement a system-level closed-loop temperature control circuit that allows real-time, bidirectional thermal regulation, and user-adjustable setpoints via onboard interface. 

Through system-level optimization, we have demonstrated prolonged cooling at skin-level temperatures under hot ambient conditions. Future work will further explore the effects of different electrode materials and geometries, initial and setpoint temperatures, and a comparative study of various heatsink designs, such as pure Ecoflex rubber, AlN composites, with/without PCM or Cu foam on overall performance. We will also examine the influence of surface color on radiative cooling and evaluate system integration on fabric platforms. Final testing will be conducted under diverse environmental conditions, including airflow scenarios, to develop a reliable, portable thermal management solution. This work aims to advance the practical application of TEDs for wearable comfort, health, and performance enhancement.