fig2

Figure 2. Structure and mechanisms of the DTTS. Structure of the DTTS: (A) Orthogonal-view schematic of the DTTS. L₁, L₂, L₃, and L₄ present the inductances of four dual-layer coils. The PDMS substrates for the top and bottom coils are not depicted; (B) Mechanism of the EC effect: (i) Interaction between (left) the c-PCL and the top coil; interaction between (right) the c-PCL and bottom coils, (ii) Cross-sectional view schematic of the relative movement between the c-PCL and one bottom coil. The legend of c-PCL represents the location of the central plane of c-PCL; (C) Circuit diagram showing the electrical interconnection between the top and bottom coils; (D) Mechanism of the Biot-Savart law: (i) Electrical connection of top and bottom coils, (ii) Cross-sectional view schematic of the relative movement between the top coil and one bottom coil; (E) Sensor deformations under normal and shear loads. P_x, P_{y, and}P_z present the loads along the x-, y-, and z-axis. DTTS: Dual tri-axial tactile sensors; PDMS: polydimethylsiloxane; EC: Eddy current; c-PCL: porous compressible layer.