Toward structural design of ultra-thin and flexible sensors
Hsieh, Ezekiel Yatung
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https://hdl.handle.net/2142/132624
Description
Title
Toward structural design of ultra-thin and flexible sensors
Author(s)
Hsieh, Ezekiel Yatung
Issue Date
2025-09-11
Director of Research (if dissertation) or Advisor (if thesis)
Nam, SungWoo
Doctoral Committee Chair(s)
Nam, SungWoo
Hsiao-Wecksler, Elizabeth T
Committee Member(s)
van der Zande, Arend
Diao, Ying
Department of Study
Mechanical Sci & Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
pectin
graphene
kirigami
Abstract
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.
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