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Author ORCID Identifier
https://orcid.org/0000-0001-7821-9035
AccessType
Open Access Dissertation
Document Type
dissertation
Degree Name
Doctor of Philosophy (PhD)
Degree Program
Polymer Science and Engineering
Year Degree Awarded
2020
Month Degree Awarded
May
First Advisor
Ryan C. Hayward
Subject Categories
Nanoscience and Nanotechnology | Polymer and Organic Materials | Polymer Science | Statistical, Nonlinear, and Soft Matter Physics
Abstract
This thesis aims to extend the understanding and explore the application of temperature-responsive hydrogel systems by integrating microelectromechanical systems (MEMS). Stimuli-responsive hydrogel systems are immensely investigated and applied in numerous fields, and interfacing with micro- and nano-fabrication techniques will open up more possibilities. In Chapter 2, the first biologically relevant, in vitro cell stretching device based on hydrogel surface instability was developed. This dynamic platform is constructed by embedding micro-heater devices under temperature-responsive surface-attached hydrogels. The fast and regional temperature change actuates the stretching and relaxation of the seeded human artery smooth muscle cell (HASMC) via controllable surface creasing instability. This device is engineered to mimic the in vivo environment of HASMCs, with independent control over substrate stiffness, mechanical cues and peptide attachment chemistry, and the response of HASMCs is inspected by the differentiation marker expression change. In Chapter 3, the swelling and deswelling kinetics of hydrogel sheets with high polymer content is inspected, with micro-heaters providing abrupt local temperature change. Poly(N-isopropylacrylamide) (PNIPAM) molecules can form hydrogen bonds with both water molecules and polymer chains, while poly(N,N-diethylacrylamide) (PDEAM) molecules can only form hydrogen bonds with water. The kinetics of the two hydrogel systems are systematically compared, revealing that while PDEAM shows one-step mass transport-limited kinetics, PNIPAM shows two-step kinetics behavior, presumably reflecting the strong influence of inter-molecular hydrogen bonding. The following two chapters document the attempts to further investigate into the hydrogel/MEMS interface. In Chapter 4, photo-patterning technique assists the study of regional modulus contrast influencing the formation of creases on the soft hydrogel surface, and it is demonstrated that the dimensions of the stiff patterns are relevant in directing the creasing direction. In Chapter 5, a photo-patternable sacrificial layer is designed based on crosslinking chemistry and gelation physics to potentially enable the construction of more complex MEMS devices.
DOI
https://doi.org/10.7275/17657663
Recommended Citation
Lu, Qi, "Nano- and micro-structured temperature-sensitive hydrogels for rapidly responsive devices" (2020). Doctoral Dissertations. 1971.
https://doi.org/10.7275/17657663
https://scholarworks.umass.edu/dissertations_2/1971
Included in
Nanoscience and Nanotechnology Commons, Polymer and Organic Materials Commons, Polymer Science Commons, Statistical, Nonlinear, and Soft Matter Physics Commons