A patient support for providing supplementary support for patients undergoing procedures such as epidurals. The first well is connected to a pad to which an external pin is connected and includes a first-type diffusion region that receives a well bias voltage. An endless chain drive transmits power from the drive sprocket to the driven sprocket, operating in a twisting three-dimensional orientation as it loops around the sprockets. The present invention realizes the shared protection in sub-wavelength level. It is also possible for all modules forming the reservoir to be subsequently inserted into the tank through the opening in the wall of the tank.