A single electrical acupuncture needle with bipolar electrodes for biotissue discrimination

In oriental medicine, acupuncture is an essential treatment for the muscle tissue relaxation. For treatment, electrical stimulations to the tissue conducted with multiple electrical acupuncture needles have generally been used. However, the sting depth of a needle can be handled only by the sense of the oriental medicine doctor. Moreover, it is difficult to use multiple needles to focus the electrical stimulation on a tissue of small volume, and, likewise difficult to distinguish various tissues. In order to overcome the aforementioned shortcomings, we developed a single acupuncture needle that has bipolar electrodes on the surface of the needle tip by using a novel flexible parylene C film photomask. The interdigitated electrodes, 31.25 μm in width and 32.00 μm in gap, were passivated by parylene C film to prevent metal debris from spreading into the tissue. The electrical acupuncture needle was developed based on the conventional acupuncture needle (400 μm in diameter), so that the needle will give a familiar sensation to patients. We demonstrate the metal patterning technique with a high resolution that has less than 2.95 % dimensional error compared to the designed metal pattern dimensions. The biotissues were well distinguished by phase angle at 1 MHz of 14.6°, -32.7°, and 43.6° for skin, muscle, and ligament of a chicken, respectively.