A Micromolding-based Evaporation-Polymerization Technique for Rapid and Tunable Fabrication of Hydrogel Films Containing Micropatterned Opal Structures
Opal-structured thin-film hydrogel materials hold great potential for utility in a wide
range of sensing applications. However, it remains significantly challenging to
synthesize these films in a rapid, inexpensive and reliable manner. Prevailing
techniques especially suffer from long opal deposition times, and often tend to involve
complex and relatively expensive steps. In this ... read morethesis, I examined a reliable, rapid and
inexpensive micromolding-based evaporation-polymerization method for fabricating poly
(ethylene glycol)-based opal-structured thin films. Specifically, intense, highly
uniform opalescent colors were achieved by filling microwells in a PDMS mold with
Polystyrene (PS) bead solution and allowing the liquid in the bead solution to evaporate
in a controlled manner so that the PS beads were arranged into a Face-centered cubic
(FCC) structure. Then, upon drying, the interstitial spaces of the packed structure were
filled with a UV-curable poly(ethylene glycol) diacrylate (PEGDA) prepolymer solution.
The prepolymer solution was polymerized under UV light and the opal-containing PEG films
recovered by peeling them off from the mold. Opal deposition using my evaporation-aided
technique reduces deposition time to 30-45 minutes only. In addition, the as-prepared
films show high tunability of opal color by simply changing PEGDA content in the
prepolymer solution. Swelling and de-swelling studies show highly reversible and tunable
responsiveness of the films to wetness, pointing to potential applications in humidity
sensing. Finally, SEM images confirm the preservation of the FCC structure of the opals
in these films.
Thesis (M.S.)--Tufts University, 2018.
Submitted to the Dept. of Chemical and Biological Engineering.
Advisor: Hyunmin Yi.
Committee: Ayse Asatekin, and Qiaobing Xu.
Keywords: Nanotechnology, Materials Science, and Chemical engineering.read less