Fabrication of metallic microstructures using exposed, developed silver halide-based photographic film

This paper demonstrates that the pattern of silver particles embedded in the gelatin matrix of exposed and developed silver halide-based photographic film can serve as a template in a broadly applicable method for the microfabrication of metallic microstructures. In this method, a CAD file is reproduced in the photographic film by exposure and developing. The resulting pattern of discontinuous silver grains is augmented and made electrically continuous by electroless deposition of silver, and the electrically continuous structure is then used as the cathode for electrochemical deposition of an additional layer of the same or different metal. The overall process can be completed within 2 h, starting from a CAD file, and can generate electrically continuous structures with the smallest dimension in the plane of the film of approximately 30 microns. Structures with aspect ratio of up to 5 can also be obtained by using the metallic structures as photomasks in photolithography using SU-8 photoresist on the top of the electroplated pattern and exposed from the bottom, followed by development and electroplating through the patterned photoresist. This method of fabrication uses readily available equipment and makes it possible to develop prototypes of a wide variety of metallic structures and devices. The resulting structures--either supported on the film backing or freed from it--are appropriate for use as passive, structural materials such as wire frames or meshes and can also be used in microfluidic, microanalytical, and microelectromechanical systems.

Microfabrication inside capillaries using multiphase laminar flow patterning

The reaction of species in solutions flowing laminarly (without turbulent mixing) inside capillaries was used as the basis for a broadly applicable method of microfabrication. In this method, patterning occurs as a result of transport of reactive species to interfaces within the capillary by laminar flow. A wide range of chemistries can be used to generate structures with feature sizes of less than 5 micrometers and with spatial localization to within 5 micrometers. The method is applicable to the patterning of metals, organic polymers, inorganic crystals, and ceramics on the inner walls of preformed capillaries, using both additive and subtractive processes.