Micro Stereo Lithography for 3D MEMS devices

摘要

Micro Stereo Lithography (MSL) is a poor man's LIGA for fabricating high aspect ratio MEMS devices in UV curable semiconducting polymers using either two computer-controlled low inertia galvanometric mirrors with the aid of focusing lens or an array of opical fibers. This technique has also been successfully used recently for fabricating 3D metallic and ceramic MEMS devices. Microfabrication techniques such as bulk micromachining and surface micromachining currently employed to conceive MEMS are largely derived from the standard IC and microelectronics technology. Even though many MEMS devices with integrated electronics have been achieved by using the traditional micromachining techniques, some limtations have nevertheless to be underlined: 1) these techniques are very expensive and need spcific installations as well as a cleanroom environment, 2) the materials that can be used up to now are restricted to silicon and metals, 3) the manufacture of 3D parts having curved surfaces or an important number of layers is not possible. Moreover, for some biological applications, the materials used for sensors must be compatible with human body and the actuators need to have high strain and displacement which the current silicon based MEMS do not provide. It is thus natural for the researchers to 'look' for alternative methods to make 3D sensors and actuators using polymeric based materials. For MSL techniques to be successful as their silicon counterparts, one has to come up with multifunctional polymers. These multifunctional polymers have not only a high sensing capability but also a high strain and actuation performance. With the invention of organic thin film transistor, now it seems possible to fabricate polymeric based MEMS devices with built-in-electronics. Moreover, with combined architecture techniques, one can integrate silicon devices with the polymeric ones without much difficulty. In this paper, the applications of MSL for polymer and ceramic based microstructures and MEMS are discussed with some examples.