FABRICATION OF HIGH-ASPECT-RATIO MICROSTRUCTURES ON PLANAR AND NONPLANAR SURFACES USING A MODIFIED LIGA PROCESS

Large surface areas (tens of square centimeters to square meters) cove red with high-aspect-ratio microstructures (HARM's) have potential app lications in a wide range of fields including heat transfer, adaptive aerodynamics, acoustics, catalysts, seal and bearing design, and compo site materials, HARM's are typically hundreds of micrometers in height , with widths ranging from a few micrometers to tens of micrometers, a nd they can be manufactured from a variety of materials such as metals , polymers, and ceramics. Three of the barriers to extensive use of la rge HARM-covered surfaces are cost, nonplanarity of typical surfaces; and adhesion of the microstructures to the surface, A starting point f or inexpensive reproduction of large arrays of HARM's is the plastic m olding step of the LIGA micromanufacturing process, In order to addres s the latter two problems, the standard LIGA process was modified/exte nded. Free-standing polymer sheets, perforated with a pattern of high- aspect-ratio throughholes, were clamped to conductive substrates. The sheets provide a template for electrodeposition of nickel microstructu res onto the target surface, This process makes it economically feasib le to electroform metal microstructures directly onto large planar and nonplanar metal surfaces (cylinders).