Diamond-like carbon coating on micropipettes

Based on glass micropipettes which are widely used in bioengineering and medicine, various microsensor probes could be produced by recent microfabrication techniques. Conductive surfaces of these sensor probes mostly need electrical insulating films coated on them, but it has been difficult to coat a high-quality and strong insulating film on a microacute probe such as a micropipette, especially on its tip. Therefore, we have employed diamond-like carbon (DLC) as an insulating film and developed a DLC coating method based on plasma chemical vapor deposition method. In the deposition apparatus, the cathode is the micropipette itself and the anode is a mesh cylinder with a central focus on the micropipette. In order to prevent the growing films from transformation due to high temperature at the tip, the voltage between the pair of electrodes is impressed intermittently. Raman spectrum and electrical resistivity measured here indicate that the deposited film is DLC and it can be worked well as an insulating film. The DLC coating method could be useful in microprobe fabrications.