Tactile sensor array on flexible substrate with piezoelectric TFT tactile sensor
View Patent ↗A flexible thin film transistor tactile sensor includes a piezoelectric semiconductor thin film channel of material whose conductivity can be electrostatically controlled connected with source and drain metals and sandwiched between bottom and top thin film insulators and at least one of a bottom and top gate metal, the sensor being supported on a flexible substrate. The piezoelectric property of the used material transduces pressure to electronic charge. The semiconductor property of the used material permits electrostatic modulation of the conductivity in TFT device architecture such that the device can be switched on and off. Transistor action provides gain for input signals, i.e., a modulation of the gate voltage induces strong current change between the source and drain, which can be leveraged to amplify the response to input pressure. The transistor forms the basis for sensor arrays, which are readily scalable to large size.
1 . A flexible thin film transistor tactile sensor, comprising: a piezoelectric semiconductor thin film channel made of a material with a conductivity that can be electrostatically controlled, the piezoelectric semiconductor thin film channel being connected with a source metal and a drain metal and being sandwiched between a bottom thin film insulator and a top thin film insulator and at least one of a bottom gate metal and a top gate metal, the flexible thin film transistor tactile sensor being supported on a flexible substrate.
2 . The flexible thin film transistor tactile sensor of claim 1 , wherein the piezoelectric semiconductor thin film channel has a thickness of 1-1000 nm.
3 . The flexible thin film transistor tactile sensor of claim 1 , wherein the material comprises ZnO, GaN or other polar materials with a polar plane aligned parallel to a surface of the flexible substrate.
4 . The flexible thin film transistor tactile sensor of claim 1 , formed as a mesa structure with the piezoelectric semiconductor thin film channel centrally located and vertically aligned with dual gates.
5 . The flexible thin film transistor tactile sensor of claim 1 , formed as a mesa structure with the piezoelectric semiconductor thin film channel centrally located and vertically aligned with the bottom gate metal and/or the top gate metal.
6 . The flexible thin film transistor tactile sensor of claim 5 , wherein the source metal and the drain metal are formed on the bottom thin film insulator, with a separation between the source metal and the drain metal to leave an opening for a central portion of the material to contact the bottom thin film insulator between ends of the source metal and the drain metal.
7 . The flexible thin film transistor tactile sensor of claim 6 , wherein the top thin film insulator leaves exposed a portion of the source metal and the drain metal for interconnection.
8 . The flexible thin film transistor tactile sensor of claim 1 , wherein the flexible substrate comprises polyimide.
9 . The flexible thin film transistor tactile sensor of claim 1 , wherein the flexible substrate comprises polydimethylsiloxane (PDMS).
10 . The flexible thin film transistor tactile sensor of claim 9 , wherein the PDMS further packages the flexible thin film transistor tactile sensor as a protection layer.
11 . The flexible thin film transistor tactile sensor of claim 1 , comprising a Parylene-C protection layer.
12 . The flexible thin film transistor tactile sensor of claim 1 , comprising a Parylene-C protection layer, wherein the source metal and the drain metal comprise thin films.
13 . The flexible thin film transistor tactile sensor of claim 1 , wherein the flexible substrate comprises polyimide, the flexible thin film transistor tactile sensor further comprising a cover layer.
14 . The flexible thin film transistor tactile sensor of claim 1 grouped with three additional sensors to form a group of four sensors to provide shear force sensing, comprising a polymer pillar formed over the group of four sensors.
15 . The flexible thin film transistor tactile sensor of claim 14 , wherein the polymer pillar comprises an L-shaped tip.
16 . The flexible thin film transistor tactile sensor of claim 14 , wherein the polymer pillar comprises a tip that is at least 25% smaller than the base of the polymer pillar.
17 . A tactile sensor array comprising a plurality of transistors of claim 1 arranged in an m×n thin film transistor (TFT) array, with m source electrodes spanning shared by sources of m TFTs in a row and n gate electrodes shared by gates of n TFTs in a column.
18 . A tactile sensor array system including a transistor of claim 1 and read-out circuitry, wherein the read-out circuitry comprises:
a gate controller configured to turn on selected ones of n gate electrodes;
amplifiers configured to amplify signals from m source electrodes; a
multiplexor to multiplex signals from the m source electrodes; an analog to digital
converter to convert signals from the m source electrodes; and
a controller configured to control the read-out circuitry to conduct read-out of sensed force encountered by the tactile sensor array system.
19 . The tactile sensor array system of claim 18 , further comprising a computer interfaced with the controller, the computer being configured to analyze date from the tactile sensor array system.
20 . The tactile sensor array system of claim 18 , comprising a computer interfaced with the controller, the computer being configured to analyze data from the tactile sensor array system, the tactile sensor array system being applied to multiple robot appendages for controlling the robot appendages, the robot appendages being controlled by a control system that controls a force applied by the appendages in real-time.
21 . The tactile sensor array system of claim 20 , wherein the robot appendages are gripper arms, and the controller evaluates average normal force applied and adjusts grip in response to maintain a predetermined normal force.
22 . The tactile sensor array system of claim 21 , wherein the controller increases the grip in response to a detected slip based upon shear force evaluation.