Silicon and Polymer Components for Microrobots

This dissertation presents the characterization and implementation of the first microfabrication process to incorporate high aspect ratio compliant polymer structures in-plane with traditional silicon microelectromechanical systems (MEMS). This discussion begins with in situ mechanical characterization of microscale polymer springs using silicon-on-insulator-MEMS (SOI-MEMS). The analysis compares microscale samples that were tested on-chip with macroscale samples tested using a dynamic mechanical analyzer. The results describe the effect of the processing steps on the polymer during fabrication and help to guide the design of mechanisms using polymers. Characterization of the dielectric breakdown of polymer thin films with thicknesses from 2 to 14 μm between silicon electrodes was also performed. The results demonstrate that there is a strong dependence of the breakdown field on both the electrode gap and shape. The breakdown fields ranged from 250 V/μm to 635 V/μm, depending on the electrode geometry and gap, approaching 10x the breakdown fields for air gaps of the same size. These materials were then used to create compliant all-polymer thermal and electrostatic microactuators. All-polymer thermal actuators demonstrated displacements as large at 100 μm and forces as high as 55 μN. A 1 mm long electrostatic dielectric elastomer actuator demonstrated a tip displacement as high as 350 μm at 1.1 kV with a electrical power consumption of 11μW. The actuators are fabricated with elastomeric materials, so they are very robust and can undergo large strains in both tension and bending and still operate once released. Finally, the compliant polymer and silicon actuators were combined in an actuated bio-inspired system. Small insects and other animals use a multitude of materials to realize specific functions, including locomotion. By incorporating compliant elastomer structures in-plane with traditional silicon actuators, compact energy storage systems based on elastomer springs for small jumping robots were demonstrated. Results include a 4 mm x 4 mm jumping mechanism that has reached heights of 32 cm, 80x its own height, and an on-chip actuated mechanism that has been used to propel a 1.4mg projectile over 7 cm

Tabletop tools for micron and sub-micron scale functional rapid prototyping

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2001.Includes bibliographical references (leaves 78-81).Three tools for the rapid prototyping of micron and sub-micron scale devices are presented. These tools represent methods for the manufacture of PEMS, or Printed micro Electro Mechanical Systems, and are enabled because they exploit the novel properties of nanocrystalline materials and their interactions with energetic beams. UV contact mask lithography was used to directly pattern metallic nanocrystals on glass and polyimide surfaces without vacuum or etching processes or the use of photoresist layers. Direct electron beam lithography of nanocrystalline metals was used to pattern multiple layer, multiple material, structures with minimum feature sizes of 100nm. Finally a micro-mirror array based selective laser sintering apparatus was built for the rapid, maskless patterning of PEMS. This tool was used to directly pattern metal structures, and for the rapid manufacture of elastomeric stamps for "nano embossing". Minimum feature sizes under 10 microns were achieved and routes to 2 micron features described. Processing time was reduced to hours from the weeks for traditional photomask / photolithography based systems. These tools are examined in the greater context of rapid prototyping technologies.Saul Griffith.S.M