Laser drilles microsieves as an alternative to etching processes and electroplating
Metalic microsieves with defined exit geometries are nowadays produced by etching methods or electrochemical deposition methods. Typically, bore diameters up to single digit micrometer range can be produced with high homogeneity of the structures. As a result of the process, conical bore geometries that limit the maximum drilling density are produced in the process, in particular at large aspect ratios between the material thickness and the drilling diameter. Additionally the material diversity of the named methods are clearly limited.
For some applications these limitations reduce the scope of aplications of the technology. For example nickel based microsieves can not be used for pharmaceutical applications due to the toxicity of nickel. Etched foils have a limited aspect ratio of about 1:2, making pressurisation of the etched microsieves with small bore diameters difficult. Laser drilled microsieves offer an alternative to the classical methods. By laser microdrilling with ultrashort pulse lasers it is possible to effectively produce microsieves from films or thin plates of almost any material. In addition to the material diversity, the reachable aspect ration is an advantage of the laser processing. For example in stainless steel films with a thickness of 100μm it is possible to produce bore diameters of 10μm or less. Thus, microsieves can be pressurerised to increase the filtration performance.