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|Ceramic Micro-Tweezers and Tips with Sensor Electrodes for Micromanipulation and Sensing|
|Keywords: micromanipulation, ceramic, sensor|
|In micromanipulation of small objects like by moving particles or by breaking off paper fibres, rigid sharp tips or micro-tweezers are needed. If those are additionally used as sensing elements, electrical contacts to the sensor are needed. Conventional micro tweezers for micromanipulation are made of silicon. Silicon, however, may be too fragile for applications, where high compression force is applied to the tweezers tips, or the surface too slippery for good adherence. An alternative material choice is aluminium-oxide (alumina), which has good mechanical strength and low chemical reactivity. Also electrical conductors by thick-film printing with various inks can be easily done for these substrates. In this paper we present results about fabrication sharp tips and micro-tweezers machined from alumina. An electrophoretic method has been used to produce additional conductive coating. Conventional laser cutting of alumina is done with CO2 lasers. This produces high aspect ratio cutting, but leaves the opposite edge teared. We have used 3ù Nd:YVO4 (355 nm) micro-machining laser (Siemens Micro Beam), which enables ~15 micron effect spot size, in comparison to 60 micron of CO2 laser. However, processing parameters have to be tuned to obtain high aspect ratio (~25) with this laser. With the method, 15 micron features can be obtained with additional benefit of accurate alignment, patterning and grinding. Grinding enables machining of thinner features on the substrate in addition to cutting. Produced tweezers were demonstrated for paper fibre measurements and electrical sensors. Sensor conductors were made of silver thick-film paste on alumina, electrophoretically coated on desired tip openings with multiwall carbon nanotube bundles (MWCNT).|
|Jouko Vähäkangas, Professor
University of Oulu