UC Riverside

As a large shift in demographic age occurs, there is a growing desire for advancements in biomedical technology. This has helped spur growth in the microelectromechanical systems (MEMS) field which has potential for the realization of devices with increased safety, efficacy, and functionality. Although material selection has largely been limited to silicon, advancements in titanium (Ti) micromachining now provide opportunities for the creation of Ti-based MEMS devices. Motivated by these breakthroughs, we discuss our recent contributions for further advancing the Ti MEMS field through: 1) Optimization of small-scale feature fabrication in titanium, and 2) the integration of high-pressure torsion (HPT) processing and Ti deep reactive ion etching (Ti DRIE) for the realization of fenestrated microneedles with enhanced material properties.

Our research on the optimization of small-scale feature fabrication in titanium was motivated by a desire to help address stent restenosis and thrombosis. A growing body of literature suggests rapid re-endothelialization of implanted stent devices may provide a means of addressing these issues. Moreover, recent evidence suggests surface topography may provide a means of modulating cell behavior, thereby facilitating stent re-endothelialization. To optimize our Ti DRIE process, we varied chamber pressure, chlorine flowrate, and oxygen flowrate to determine their effects upon the resulting structures. In doing so, we identified critical parameters for sidewall passivation and successfully created rationally-designed surface patterning features as small as 150 nm which represents a five-fold or greater improvement compared to other processes in literature.

Our second research endeavor regarding the integration of HPT processing and Ti DRIE was motivated by the desire to enhance the material properties of Ti without changing its composition. HPT processing was used to refine the grain size of Ti substrates and x-ray diffraction, indentation testing, and microscopy were used to characterize the changes in microstructure and mechanical properties. Significant improvements were observed, and we successfully utilized Ti DRIE to fabricate fenestrated microneedles out of the enhanced material. Collectively, these results represent significant advancements in the Ti MEMS field and illustrate key steps towards the realization of Ti-based MEMS devices with enhanced functionality and customizable properties.