Copyright 2016 Biomedical Microdevices Laboratory
Titanium micromachining
The extraordinary opportunity afforded by MEMS has driven significant effort to extend its application towards biomedical devices. However, continuing reliance upon micromechanical materials adopted from the semiconductor industry may ultimately limit the scope of what can be achieved. Many such materials suffer from poor mechanical reliability due to low fracture toughness, which results in extreme sensitivity to stress concentration and predisposition to catastrophic failure by fracture. Although mitigation via robust design and packaging is sometimes possible, this invariably increases complexity and cost. Moreover, in many emerging applications, these avenues are not available, due to design constraint and/or performance restriction, thus underscoring need for development of viable alternatives.
A short time ago, we reported the development of techniques that enable, for the first time, deep etching of bulk titanium [1,2]. Titanium possesses high fracture toughness, which enhances reliability through graceful, plasticity-based failure. Moreover, titanium is of particular interest for biomedical applications, due to its proven biocompatibility in chronic implantation. Our new techniques provide opportunity to leverage these advantageous characteristics by enabling fabrication of titanium-based MEMS devices with a degree of design sophistication that would be difficult if not impossible to achieve with prevailing metal micromachining methods (see Figures). Moreover, these techniques fully leverage existing semiconductor process infrastructure, thus ensuring scalability to low-cost/high-volume manufacturing, as well as opportunity for high-density multifunctional integration.
The extraordinary opportunity afforded by MEMS has driven significant effort to extend its application towards biomedical devices. However, continuing reliance upon micromechanical materials adopted from the semiconductor industry may ultimately limit the scope of what can be achieved. Many such materials suffer from poor mechanical reliability due to low fracture toughness, which results in extreme sensitivity to stress concentration and predisposition to catastrophic failure by fracture. Although mitigation via robust design and packaging is sometimes possible, this invariably increases complexity and cost. Moreover, in many emerging applications, these avenues are not available, due to design constraint and/or performance restriction, thus underscoring need for development of viable alternatives.
A short time ago, we reported the development of techniques that enable, for the first time, deep etching of bulk titanium [1,2]. Titanium possesses high fracture toughness, which enhances reliability through graceful, plasticity-based failure. Moreover, titanium is of particular interest for biomedical applications, due to its proven biocompatibility in chronic implantation. Our new techniques provide opportunity to leverage these advantageous characteristics by enabling fabrication of titanium-based MEMS devices with a degree of design sophistication that would be difficult if not impossible to achieve with prevailing metal micromachining methods (see Figures). Moreover, these techniques fully leverage existing semiconductor process infrastructure, thus ensuring scalability to low-cost/high-volume manufacturing, as well as opportunity for high-density multifunctional integration.
Current Research
Representative publications:
[1] MF Aimi, MP Rao, NC MacDonald, AS Zuruzi, and DP Bothman. Nature Materials 3(2):103-05, 2004.
[2] ER Parker, MF Aimi, BJ Thibeault, MP Rao, and NC MacDonald. J Electrochem Soc 152(10): C675-83, 2005.
[1] MF Aimi, MP Rao, NC MacDonald, AS Zuruzi, and DP Bothman. Nature Materials 3(2):103-05, 2004.
[2] ER Parker, MF Aimi, BJ Thibeault, MP Rao, and NC MacDonald. J Electrochem Soc 152(10): C675-83, 2005.
Top: Scanning electron micrograph of a
titanium micromirror device [1].
Bottom: Scanning electron micrograph of a titanium interdigitated electrode structure [2].
Bottom: Scanning electron micrograph of a titanium interdigitated electrode structure [2].