Microscopic Medical Instruments on Road to Becoming Highly Functional

Nozomu Mishima, Tsuneo Kurita, and others of the Environmentally Conscious Design and Manufacturing Group, the Advanced Manufacturing Research Institute, the National Institute of Advanced Industrial Science and Technology (AIST) have developed a combined laser and electrochemical machining system that can machine a microscopic metal tube with a diameter of less than 100 µm into a complex shape. Machining of high-value added devices can be realized by applying the technology, for example, to catheters or stents for brain surgery or to contact probes for inspection of high-density electronic circuits, for which no existing microscopic complex machining technology has so far been applicable.

Existing machining technologies have several problems: machining is sometimes impossible because the minute tube to be machined and the working tool come into contact with each other at a point other than the machining position; a tube of too small a diameter cannot be machined because it is easily bent by the tool contact force during machining; and finally, a general problem in any minute tube machining technology is that the tube cannot be precisely held. As a result of these problems, it has been difficult to machine a metal tube of a diameter of less than 300 µm into a complex shape.

The newly developed system adopts a non-contact laser machining technology in which the tube is not subjected to force during machining. As the same laser light source is used for both machining and measurement, no displacement appears between the measured and the machined positions, and the laser beam is incident on the precise position by means of an error-compensation—even if the target tube has holding-position errors in rotating center and slope. Through electrochemical finish machining, the heat-affected layer inherent to laser machining is removed to provide a smooth surface. Once attached, the machining workpiece does not need to be detached during the two-step processes, and a stainless tube the size of a human hair can be machined into a complex shape.