3D printing of moldless flexible pressure sensor using Bingham plastic

다국어 초록 (Multilingual Abstract)

Devices made from stretchable electronic materials are under huge interest as future application for wearable device in means for clothing or directly attached sensor. Such materials have typically been prepared by engineering elastomeric materials such as silicon. With their flexible characteristic, the response to the external mechanical deformation have also drawn much attention.
Here we studied 3D printed flexible and moldless fabricated pressure sensor. Using 3D printer to freely direct write resistance electrode, the extruded CNT/PDMS sensor was studied to verify whether the geometric structure influences the sensor’s sensitivity. Moreover, this methodology could substitute the complicated steps commonly used for fabrication of 3D structure or PDMS molding such as lithography or etching. The 3D printing of viscoplastic elastomer while maintaining its structure after extrusion without collapsing was possible when printing was proceeded inside the Bingham.
In order to test the conductive composite’s response to external mechanical deformation, the gauge factor of CB/PDMS with different structure was studied. Afterwards CNT/PDMS as resistive electrode was printed for pressure sensor structure. The structure is uniformly aligned with independently arrayed deformable pyramidal tips that each of them works as a resistive sensor tip. The easily deformable pressure sensors are designed regarding the shape factor that effect the shape of elastomer as its compressibility in response to external pressure. The counter electrode was easily printed through commercial office printer using silver nanoparticle ink on PET film or Sonoplot. When the external pressure is introduced, a potential difference with respect to 3D printed resistive elastomer structure can induce electric current flow through the contact area by bridging the two electrode terminals.
Three geometrically different pyramidal sensors were fabricated with different bottom square edge to height ratio to test the sensitivity variation through structure transition. The sensitivity and detection range of three sensors all differed from 0 to 1300 Pa. From this conclusion, the hypothesis that shape of sensor highly affects the sensitivity and detection range was confirmed.