A Study on the Pressure Sensor Mounted onto the 3D Printed Prosthetic Socket for Motion Monitoring

초록

The importance of 3D printing in manufacturing products quickly and cheaply for many industries is growing on a daily basis. For medical applications, 3D printing technology is applied to manufacture customized prosthetic hand and leg sockets for amputees. It is easier to modify the socket manufactured by 3D printing rather than the conventional process. Furthermore, it can reduce costs and time due to a minimal manufacturing period. Pressure monitoring indicates that the pressure sensors are mounted onto the 3D printed prosthetic socket which detects the small pressure changes in an amputated area. Here in, capacitive pressure sensors and prosthetic sockets were manufactured by using 3D printing. It measured the pressure values between skin and socket while users wearing the socket.It seems that the skin of a residual limb is weaker compared to the normal skin which means that a small amount of pressure can damage the skin tissue. So, the inner part of the socket was manufactured using Thermoplastic Polyurethane (TPU) which has soft properties and flexibly connects with the residual limb. The outer part is made from Poly Lactic Acid (PLA) to protect an amputated area that can withstand external impact. The capacitive pressure sensors were manufactured by using a multi-extruder 3D printer. The inner part of the sensor is made from conductive PLA and the outer part with TPU. The conductive PLA was used to obtain an electric signal. TPU was used for accurate measurements and improved sensitivity. Ecoflex was used as a dielectric and capacitance values with respect to pressure values were obtained by AD7747 board. The pressure sensors were installed in circular shapes at an interval of 90 degrees to monitor the pressure acting on the socket and residual limb. Various arm movements were considered to monitor the pressure changes while performing several tasks such as transferring the block, flipping the paper, and moving light/heavy things.