Strain-insensitive soft pressure sensor and method of measuring pressure

1 . A soft pressure sensor comprising:

a stretchable top electrode comprising a first elastomeric layer;

a stretchable bottom electrode comprising a second elastomeric layer;

an array of peaked structures between the stretchable top and bottom electrodes, the peaked structures comprising an array of stiffening electrodes on the stretchable bottom electrode and a continuous film conformally overlying the array of stiffening electrodes, the continuous film conforming to a shape of each of the stiffening electrodes such that protruding regions are formed in the continuous film, where a tip of each protruding region is in contact with the stretchable top electrode and a base of each stiffening electrode is in contact with the stretchable bottom electrode, and

one or more spacers extending between and bonded to the stretchable top electrode and the continuous film on the stretchable bottom electrode, each of the one or more spacers being positioned outside the array of peaked structures,

wherein a capacitance measured by the soft pressure sensor is substantially invariant under in-plane stretching.

2 . The soft pressure sensor of claim 1 , wherein the peaked structures have a pyramidal, dome-shaped, conical, or another deformable shape.

3 . The soft pressure sensor of claim 1 , wherein the continuous film comprises an ionically conductive elastomer or ion gel.

4 . The soft pressure sensor of claim 3 , wherein the stretchable top electrode comprises a first conductive layer on the first elastomeric layer, and the tip of each protruding region is in contact with the first conductive layer, and

wherein the stretchable bottom electrode comprises a second conductive layer on the second elastomeric layer, and the base of each stiffening electrode is in contact with the second conductive layer.

5 . The soft pressure sensor of claim 1 , wherein the one or more spacers comprise an elastomer.

6 . The soft pressure sensor of claim 1 , wherein the stiffening electrodes have a stiffness of at least about 0.3 GPa.

7 . The soft pressure sensor of claim 1 , exhibiting a pressure sensitivity of at least about 2 kPa- 1 and/or a strain insensitivity of at least about 98% up to 50% strain.

8 . The method of claim 1 , wherein the capacitance is an electric double layer (EDL) capacitance.

9 . The soft pressure sensor of claim 1 , wherein the tip has a radius of curvature in a range from 0-30° to ensure a small region of contact between the protruding regions and the stretchable top electrode.

10 . The soft pressure sensor of claim 1 , wherein the stiffening electrodes have a stiffness of at least about 1 GPa.

11 . The soft pressure sensor of claim 1 , further comprising an electrically conductive adhesive between the continuous film and the stretchable bottom electrode in regions between the stiffening electrodes.

12 . A method of measuring or monitoring pressure, the method comprising:

attaching the soft pressure sensor of claim 1 to a part or an appendage of a human body or soft robot;

contacting an object with the soft pressure sensor;

measuring a capacitance of the soft pressure sensor, thereby obtaining touch information during the contacting.

13 . The method of claim 12 , further comprising transmitting the capacitance measured by the soft pressure sensor to a closed loop controller; and

adjusting a position of the part or appendage with respect to the object to achieve a predetermined capacitance and thus a preset pressure.

14 . The method of claim 12 , wherein, as the soft pressure sensor is stretched or bent to accommodate motion of the part or appendage, the capacitance measured by the soft pressure sensor is substantially unchanged.