Date of Last Revision

2023-05-03 12:52:47


Chemical Engineering - Cooperative Education

Degree Name

Bachelor of Science

Date of Expected Graduation

Spring 2019


The tested hypothesis was that features on polydimethylsiloxane (PDMS) surfaces coated with a poly(N-isopropylacrylamide)/aminopropyltriethoxysilane or pNIPAAM/APTES thin film would accelerate cell detachment than the film coated on a unfeatured surface. This project tested samples with features generated by molds, wrinkling, and sandpaper roughened substrates. Surface feature generation methods were limited to mechanical means, and characterized by microscopy and strain rates. 50/50 mixtures of 1.5 wt.% pNIPAAM/ APTES were used to coat thin films (30-40 nm) on PDMS membranes by spin-coating, and the coated membranes were thermally annealed to chemically graft pNIPAAm/APTES on the membrane and their thermo-responsive property was assessed by water contact angle at a temperature above and below the transition temperature of pNIPAAm (i.e., 32°C). The contact angle was found to be 47.7° at 25°C and 95° at 40°C, illustrating the thermo-responsivity was achieved. . They were then seeded with human mesenchymal stem cells and incubated at 37 °C until cells reached confluence, after which, they were cooled to room temperature to allow cell detachment. The fastest detachment results came from surfaces wrinkled using a 1-dimensional strain of 0.5, with wavelengths and depth of features at the micron scale. On these surface, the first group of cells detached in 12 min , and all cells detached in 22 min, as compared to 14 min and 44 min for pNIPAAm/APTES on featureless membrane. The featured membranes were shown to significantly improve cell detachment, by allowing water to flow through channels, created by wrinkling, below the cells to accelerate pNIPAAm film hydration, hence speeding up cell detachment.

Research Sponsor

Dr. Bi-Min Newby

First Reader

Nic Leipzig

Second Reader

Edward Evans



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