Increased Force Generation in Electroactive Polymers

• US 20160036353A1
• Filed: 07/31/2015
• Published: 02/04/2016
• Est. Priority Date: 07/31/2014
• Status: Active Grant

• Current Assignee: Battelle Memorial Institute
• Original Assignee: Battelle Memorial Institute
• Inventors: Stasik, Mark C., Sayre, Jay R.
• Granted Patent: US 9,951,757 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: F03G 7/005 Electro-chemical actuators; Actuators having a material for absorbing or desorbing gas, e.g. a metal hydride; Actuators using the difference in osmotic pressure between fluids; Actuators with elements stretchable when contacted with liquid rich in ions, with UV light, with a salt solution

Abstract

Methods and systems are provided for combined direct current and alternating current activation of electroactive polymer devices. The combined direct current and alternating current activation may increase force generation compared to activation using direct current alone. For example, a method for actuating an electroactive polymer device may include providing the electroactive polymer device. The electroactive polymer device may include a first electrode and a second electrode electrically coupled to an electroactive polymer. The method may include applying a direct current across the electroactive polymer via the first and second electrodes. The method may include applying an alternating current across the electroactive polymer. The direct current and the alternating current may be effective to cause actuation of the electroactive polymer device.

Claims

1. A method for actuating an electroactive polymer device, comprising:

providing the electroactive polymer device, the electroactive polymer device comprising a first electrode and a second electrode electrically coupled to an electroactive polymer;

applying a direct current across the electroactive polymer via the first and second electrodes; and

applying an alternating current across the electroactive polymer,

the direct current and the alternating current being effective to cause actuation of the electroactive polymer device.

2. The method of claim 1, the direct current and the alternating current being effective to cause actuation of the electroactive polymer device to exert a greater force compared to actuation of the electroactive polymer device using the direct current alone.

3. The method of claim 1, the applying the alternating current across the electroactive polymer comprising applying the alternating current across the electroactive polymer via the first and second electrodes.

4. The method of claim 1, the applying the alternating current across the electroactive polymer comprising inducing the alternating current in the electroactive polymer.

5. The method of claim 1, the direct current being applied at a voltage in VDC and the alternating current being applied at a voltage amplitude in VAC, an absolute value of a ratio of the voltage in VDC divided by the voltage amplitude in VAC being at least about 3:

1.

6. The method of claim 1, the electroactive polymer device being characterized by a capacitance, the capacitance being characterized by a resonant frequency, and the alternating current being applied at an AC frequency selected to at least partly couple with the resonant frequency.

7. The method of claim 6, further comprising determining one or both of the capacitance and the resonant frequency characteristic of the capacitance.

8. The method of claim 7, the determining the resonant frequency characteristic of the capacitance comprising:

determining the capacitance as a function of frequency; and

determining the resonant frequency according to a peak in the capacitance as a function of frequency.

9. The method of claim 7, the determining the capacitance comprising:

determining an impedance of the electroactive polymer device, the impedance value being determined at a corresponding frequency; and

calculating the capacitance according to;

10. The method of claim 1, the electroactive polymer device comprising a power supply configured to provide the direct current and the alternating current, the applying the direct current and the applying the alternating current comprising controlling the power supply.

11. The method of claim 1, further comprising controlling one or more of:

a moisture content of the electroactive polymer device and a humidity level of an environment in which the electroactive polymer device is actuated.

12. An electroactive polymer actuator system, comprising:

an electroactive polymer device, the electroactive polymer device comprising a first electrode and a second electrode electrically coupled to an electroactive polymer layer;

a power supply operatively coupled to the first and second electrodes;

a controller, the controller being programed with instructions for controlling the power supply to;

apply a direct current across the electroactive polymer layer via the first and second electrodes; and

apply an alternating current across the electroactive polymer layer,

the direct current and the alternating current being applied effective to cause actuation of the electroactive polymer device.

13. The electroactive polymer actuator system of claim 12, the direct current and the alternating current being effective to cause actuation of the electroactive polymer device to exert a greater force compared to actuation of the electroactive polymer device using the direct current alone.

14. The electroactive polymer actuator system of claim 12, the controller being programed with instructions for controlling the power supply to apply the direct current at a voltage in VDC and to apply the alternating current at a voltage amplitude in VAC, an absolute value of a ratio of the voltage in VDC divided by the voltage amplitude in VAC being at least about 3:

1.

15. The electroactive polymer actuator system of claim 12, the electroactive polymer device being characterized by a capacitance, the capacitance being characterized by a resonant frequency, and the controller being programed with instructions for controlling the power supply to apply the alternating current at an AC frequency selected to at least partly couple with the resonant frequency.

16. The electroactive polymer actuator system of claim 12, further comprising an impedance sensor, the controller being programed with instructions for controlling the impedance sensor and the power supply to determine a capacitance of the electroactive polymer device 100 and a resonant frequency characteristic of the capacitance.

17. The electroactive polymer actuator system of claim 16, the controller being programed with instructions for controlling the impedance sensor and the power supply to determine the capacitance, the instructions comprising:

determining an impedance of the electroactive polymer device using the impedance sensor 306, the impedance value being determined at a corresponding frequency; and

calculating the capacitance according to;

18. The electroactive polymer actuator system of claim 12, the electroactive polymer device comprising one or more of:

an ionic polymer metal composite and an ionic electroactive polymer layer.

19. The electroactive polymer actuator system of claim 12, the electroactive polymer device comprising an electroactive polymer laminate structure comprising:

a first ion conducting binder layer and a second ion conducting binder layer;

an electroactive polymer layer, the electroactive polymer layer being laminated between the first and second ion conducting binder layers; and

a first electrode and a second electrode laminating the first and second ion conducting binder layers and the electroactive polymer layer therebetween,

the electroactive polymer layer, the first and second ion conducting binder layers 106, 108, and the first and second electrodes being operatively coupled to form the electroactive polymer laminate.

20. The electroactive polymer actuator system of claim 12, further comprising a moisture or humidity control device.