A novel ultra-violet assisted anisotropic etching of plastic to realize micro-gears

Abstract

An ultraviolet assisted chemical etching of plastic is reported in which the etching of PET substrates is anisotropic in the direction of light illumination. A strong solvent as di-methyl-formamide (DMF) is exploited to perform the chemical etching process and patterning of the desired structures is feasible using a Ge/Cu bi-layer as the masking film. Etch rate depends strongly on the intensity of the ultra-violet light and temperature of the solution during this etching process. An average etch rate of 15um/h is achieved with little mask undercut in the presence of 6–8 mW/cm2 of 365 nm UV at a temperature of 120 degrees C. The highest achieved etch rate in this technique is 40um/h using an intensity of 16 mW/cm2 for the UV illumination. The effects of solution temperature during etching, the intensity of light, and the amount of the solvent above the sample have been studied. This technique has been applied to etch 80um of PET substrates and to make 40um thick square membranes with an area of 500um × 500um. Also 120um thick micro-gears have been realized with a diameter of 900um. The gears have been freed and installed on their corresponding axels with a diameter of 100um.