Polymer based microscale and nanoscale technologies for optical and biomedical application

Date
2016-01-01
Authors
Dhakal, Rabin
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Jaeyoun Kim
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Electrical and Computer Engineering
Abstract

Polymer based micro and nano systems has emerged as a mainstream research in recent times with advent of bio-inspired design of opto-MEMS as wells as bio-MEMS. Polymers have tunable materials characteristics ranging for elastic to brittle nature, optically transparent and biocompatible and biodegradable for application in optics and biomedicine. I tackled four different technological challenges in this research work using novel biomimetic design and biopolymers as listed below.

First, I designed wide acceptance angle thin and flat miniaturized solar concentrator by mimicking the wide acceptance angle found in compound eye of insects. I integrated lens, conic spacer and light guide to concentrate and redirect sunlight into small area where PV cell can be installed. My design can have total concentration up to ~40 for acceptance angle of 15à °.

Second, I designed and fabricated automated light control switch using IR part of solar spectrum and to change a paraffin micro-chamber volume and actuate the cantilever structure. The cantilever structure when activated frustrates the TIR guided light in the lightguide and control the illumination level. We obtained rms value of illumination change to be 0.012 for input change of 0.018.

Third, I developed rapid, inexpensive, reproducible method to make nanoscale patterns in PLLA films using replica-molding techniques. We produce very high fidelity replication of PLLA using double replication from master polycarbonate to PDMS mold and from PDMS mold to PLLA film by drop casting process. The surface characteristics of the nano-patterned film changed drastically form hydrophilic to hydrophobic due to patterning. We also investigate the drug coating process in this film for its use in controlled drug release platform.

Finally, I used the drug coated and nano-patterned PLLA film for its potential application in biodegradable coronary stents. We fabricated the stents by rolling the PLLA films into the tube. The controlled drug release was studied by releasing the control and patterned PLLA surface into phosphate buffer saline. We used advanced high performance liquid chromatography coupled with mass spectrometer to measure the amount of drug released as a function of time. The nano-patterned surface has up to 20% slower drug release rate in comparison to the flat surface.

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