Fabrication and characterization of 3D printing flexible capacitive pressure sensor for wearable device and biomechanical applications

Biological monitoring technology based on pressure sensing is a very useful for human diagnosis method as an assistive equipment, which should be comfortable on wearing position for user as well as and patient. Especially, pressure monitoring for prosthetic arm and artificial leg is the critical element to maintain the safety of the amputees. In this research, the fabrication and characterization of a novel flexible pressure sensor was done to measure the actual working pressure between the surface of human body and assistive device for biomechanical techniques. The ultimate goal of the sensor design is targeted for use in robotic and prosthetic limb, where feedback and ability to detect forces associated with slip is crucial point. To fabricate the capacitive type pressure sensor, finite element method (FEM), additive manufacturing (3D-printing) and signal processing were used. FEM simulation was performed with Comsol S/W for optimal structure design to evaluate with the structural deformation and maximum capacitance value up to 500 kPa in sensor range. Sensor with a full scale volume thickness under 10 mm were produced using FDM 3D-printingtechnique. A passive two-terminal electrical component part of capacitive pressure sensor was fabricated with conductive thermoplastic material and medium side of dielectric layer to keep soft and flexible structure. The output signal from the pressure sensor and related signal processing system was connected to a voltage divider circuit to amplifying the signal, multiplexer, microcontroller unit included analog to digital converter and indicating program. As a result, capacitive pressure sensing technology embedded in 3D printed structure can be considered for maintenance of stability and comfortability to amputees.