The fabrication process for the tactile sensor based on Co AW and the air gap structure is shown in fig. S3.
The authors chose to use a co-based amorphous wire (Co AW) for its strong magnetic properties. The researchers were able to use a B-H Loop Tracer machine to test the permeability of the wire. This test showed that as increasing frequency was applied, the wire was able to maintain a high permeability and impedance.
Additionally, the authors determined the correct thickness of the PDMS ring and free standing membrane that would allow a sufficient air gap to be present between the magnetic particles and inductor. The air gap allows for pressure-induced deformations in the membrane which is detected by the changes in the magnetic flux through the inductor.