Date of Award
Doctor of Philosophy
Electrical and Computer Engineering
Bioengineering is an emerging field of study which bridges life science and engineering. At its early stage, bioengineering was commonly recognized as biomedical engineering. This focused mainly on the biomedical aspects with the engineering playing only assistive roles. Pharmaceutical researches, such as cell mechanics, vascular biology, and neural engineering, have been performed as its sub-categories. Later, with increased emphasis on the engineering aspect, a new phase of bioengineering has emerged. Biomimetics, the effort to mimic nature and utilize biological inspirations, is this new branch.
The advances in microfabrication techniques during the last few decades have further promoted bioengineering. Micro/electromechanical systems (MEMS) technologies to obtain microscale total assay systems (µTAS) have led to microfluidics studies that are directly related to biomedical studies. Soft lithography and polymer MEMS have facilitated the development of biomimetics.
Despite rapid advancement in the field of bioengineering, many areas of development remain. This especially pertains to miniaturization, cost deduction, and ease of fabrication in polymer MEMS technologies, which are crucial in both biomedical and biomimetic aspects. However, the broad and inclusive nature of bioengineering makes it difficult to choose a particular subject to focus on. Therefore, we extracted key factors in bioengineering: microfluidics, bio-inspired structures, polymer MEMS, and their sensor applications. In accordance, I will present four platform technologies which are correlated to all key factors synergistically.
First, the optofluidic waveguiding was studied to enhance sensing capability in biomedical studies. Utilization of optical components in sensing scheme has been attracting interests for its electromagnetic interference (EMI)-free nature. However, one of the biggest difficulties in optofluidic sensing is that the liquid core generally exhibits refractive index lower than the solid claddings, making total internal reflection impossible. A design which adopts anti-resonance reflection optical waveguiding (ARROW) scheme was designed and analyzed with 2D numerical simulations.
Secondly, polymer MEMS technology was investigated to make bio-inspired optical waveguiding structures. There have been growing demands for polymer microwires due to their actuator and sensor potentials. By utilizing poly(dimethylsiloxane) and sacrificial water-soluble wax in combination, we could generate two dimensional arrays of microscale polymer waveguides that are strongly attached to the super/substrate. Mechanical and optical characterizations were performed to show its potentials.
Thirdly, a gas flow sensor was developed based on the previously developed polymer microwire. Due to its flexibility, the microwire can be elongated up to a few times its original length in addition to its tension and resistance to the outside mass flow increased. By investigating their relationship, we have shown the potential of the microwire to be used as a tunable optical gas flow sensor.
Finally, we developed a new and easy method to mimic biological blood vessels with microfluidic channels completed with circular cross-sections and three dimensional (3D) topologies. We have found the biomaterial which makes the fabrication simple, safe, cost-effective, and environment-friendly. As an example, we produced complex 3D assemblies of channels with their diameters ranging between 30 to 400 µm.
When integrated synergistically, these unit structures and functionalities, mainly based on optical and/or polymer technologies, will greatly facilitate the realization of future bioengineering application systems.
Ji Won Lee
Lee, Ji Won, "Microscale platform technologies for biomimetics and biomedical engineering" (2012). Graduate Theses and Dissertations. 12685.