BME MS Thesis Defense - David Li

11:00 am on Thursday, April 17, 2014
44 Cummington Mall, Room 705
Title: "Biomimetic modifications to microfluidic silk spinning"

Joyce Wong (Advisor, Chair)
Michael Smith
David Kaplan

Silk fibers from arthropods possess several favorable properties for biomedical applications, including high mechanical strength and biocompatibility. However, the majority of silk fiber production is currently limited to manipulation of cocoons from the Bombyx mori silkworm. It should be possible to make this process more efficient by dissolving waste silk threads leftover from this manipulation and using artificial spinning techniques to spin those proteins back into usable fibers. Once this artificial spinning technique has been perfected, it may be possible to use similar designs to spin recombinant silk proteins into threads with more favorable mechanical properties. As such, a method is needed to artificially spin silk protein into fibers with comparable properties to naturally-derived silk threads.

Current microfluidic devices are limited to spinning B. mori silk into weak, poorly-formed fibers. The incorporation of silk gland-like ion gradients and high shear stress into current and novel microfluidic devices is theorized to improve mechanical properties of resultant spun silk. To this end, ion gradients were added to the current microfluidic device. In addition, a novel microfluidic device was developed to increase shear stress. After investigating the individual effects of ion gradients and shear stress on the silk spinning process, an integrated microfluidic device was designed to investigate the combined effects. Computational models of the flow within each microfluidic device were generated and used to predict biomimetic design parameters. Measurements of fiber diameter and pH within the microfluidic devices were collected to verify the accuracy of the computational models. ATR-FTIR, and mechanical testing measurements were collected to characterize and compare resultant fibers. From these results, relationships were found between the incorporation of ion gradients and shear stress into the spinning process and the properties of the fibers produced.