Toward structural design of ultra-thin and flexible sensors

Developing the next generation of flexible and wearable sensors will require concurrent improvements in both the materials and mechanics that such sensors are built upon. In this dissertation, I build upon prior work developing stretchable kirigami graphene sensors and flexible temperature-sensing pectin films to further improve their performance, robustness, sensitivity, and application. My first study presents a kirigami-patterned graphene mesh structure that achieves multiaxial stretchability and multifunctional sensing with minimal motion artifacts. I demonstrate insensitivity to multiaxial strain, including 180° torsion and 100% biaxial strain. As a proof-of-concept, I show a biaxially stretchable kirigami graphene sensor array capable of temperature and glucose concentration sensing with robust signal stability. My second study presents thermal radiation sensors based on ionic-conducting pectin films. I first improve on prior art by increasing the robustness and reliability of temperature-sensitive pectin films, extending their performance lifetimes from several hours to several days. I then demonstrate the resulting robust pectin film sensors in an array configuration for thermal radiation sensing and validate their performance against theoretical models for radiative heat transfer. My final study combines the two previous works by integrating graphene electrodes together with pectin films in a novel geometric configuration. In particular, I show that switching the current direction from across the lateral dimension of the pectin thin films to through their thickness drastically increases the baseline conductivity. I additionally present some equivalent electric circuit models for electric conduction through pectin film sensors and discuss how different configurations and materials play a role in the overall performance. I lastly demonstrate the novel graphene-pectin composite sensors in an array configuration as a fully optically transparent touch-free interface for detecting user input.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Hsieh, Ezekiel Yatung

Contributors dc:contributor

• Nam, SungWoo
• Hsiao-Wecksler, Elizabeth T
• van der Zande, Arend
• Diao, Ying

• pectin
• graphene
• kirigami

Statement dc:rights

• Copyright 2025 Ezekiel Hsieh

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132624

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132624