2026-09-18T20:17:46Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/132624 2026-03-24 col_2142_5131 col_2142_14787 com_2142_5130 com_2142_9630 com_2142_234

application/pdf en text Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2027-12-01 The student, Ezekiel Hsieh, accepted the attached license on 2025-09-10 at 12:45. The student, Ezekiel Hsieh, submitted this Dissertation for approval on 2025-09-10 at 12:53. This Dissertation was approved for publication on 2025-09-11 at 16:00. DSpace SAF Submission Ingestion Package generated from Vireo submission #22798 on 2026-02-19 at 18:45:30 Toward structural design of ultra-thin and flexible sensors Hsieh, Ezekiel Yatung 2025-09-11 Nam, SungWoo Nam, SungWoo Hsiao-Wecksler, Elizabeth T van der Zande, Arend Diao, Ying pectin graphene kirigami eng 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. 2025-12 Thesis https://hdl.handle.net/2142/132624 Copyright 2025 Ezekiel Hsieh Mechanical Sci & Engineering Mechanical Engineering University of Illinois Urbana-Champaign Ph.D. Dissertation