Composite electroactive material for electromechanical actuators
View Patent ↗A composite electroactive material having a plurality of particle cores, each particle core surrounded by a polymer covering having one or more strands of an electroactive polymer. In one embodiment, the particle cores have a relatively small size, e.g., between about 10 and 50 nm, and include a material having a relatively large dielectric constant, e.g., greater than about 30. Each polymer strand includes an electroactive elastomer that is bonded to the surface of the corresponding particle core by a linker. Representative examples of the particle core material, elastomer, and linker are titanium dioxide, polybutadiene, and a phosphonate group, respectively.
1. An apparatus, comprising:
first and second electrodes; and
a layer of an electroactive material located between the electrodes, wherein:
the electroactive material comprises a plurality of particle cores, each particle core surrounded by a polymer covering having one or more strands of an elastomeric polymer, the particle cores having linear dimensions smaller than about 0.5 micron; and
the layer is bound in a manner that enables a layer thickness to respond to application of a voltage differential between the first and second electrodes.
2. The invention of claim 1 , wherein:
the first and second electrodes and the layer have substantially cylindrical shapes that define an inner channel; and
the apparatus is adapted to propel fluid along the channel in response to the application of the voltage differential.
3. The invention of claim 1 , wherein the first and second electrodes form a parallel-plate capacitor.
4. The invention of claim 1 , wherein the layer is in contact with the first and second electrodes.
5. The invention of claim 1 , wherein the electroactive material has a dielectric constant greater than about 10.
6. The invention of claim 1 , wherein the particle cores comprise a material having a dielectric constant of at least about 30.
7. The invention of claim 1 , wherein the particle cores occupy at least about 10% of the total volume in the electroactive material.
8. The invention of claim 1 , wherein the particle cores have sizes between about 10 and 100 nm.
9. The invention of claim 1 , wherein the particle cores comprise at least one of a metal niobate, a metal oxide, a metal titanate, a metal tantalite, a metal sulfide, a metal selenide, and a metal telluride.
10. The invention of claim 1 , wherein each polymer strand comprises an elastomer, which is chemically bonded to the corresponding particle core via a linker.
11. The invention of claim 10 , wherein the elastomer comprises at least one of polybutadiene, polyisoprene, polyisobutylene, and polyurethane.
12. The invention of claim 10 , wherein the linker is a phosphonate group, a silyl group, or a carboxylic group.
13. The invention of claim 10 , wherein the electroactive material has an elastic modulus that does not exceed an elastic modulus of the elastomer by more than about 100%.
14. The invention of claim 1 , wherein one or more of said strands are chemically bonded to the particle core.
15. The invention of claim 1 , wherein said thickness decreases in response to said voltage application.
16. An electroactive material, comprising a plurality of particle cores, each particle core surrounded by a covering having one or more strands of an elastomeric polymer, the particle cores having linear dimensions smaller than about 0.5 micron, wherein:
each polymer strand comprises an elastomer, which is chemically bonded to the corresponding particle core via a linker; and
the elastomer comprises at least one of polybutadiene and polyisoprene.
17. The invention of claim 16 , wherein:
the electroactive material has a dielectric constant greater than about 10;
the particle cores comprise a material having a dielectric constant of at least about 30;
the particle cores occupy at least about 10% of the total volume in the electroactive material; and
the particle cores have sizes between about 10 and 100 nm.
18. The invention of claim 16 , wherein:
the particle cores comprise at least one of a metal niobate, a metal oxide, a metal titanate, a metal tantalite, a metal sulfide, a metal selenide, and a metal telluride;
the elastomer further comprises at least one of polyisobutylene and polyurethane;
the linker is a phosphonate group, a silyl group, or a carboxylic group; and
the electroactive material has an elastic modulus that does not exceed an elastic modulus of the elastomer by more than about 100%.
19. The invention of claim 16 , wherein the elastomer comprises polybutadiene.
20. The invention of claim 16 , wherein the elastomer comprises polyisoprene.
21. An apparatus, comprising:
first and second electrodes; and
a layer of an electroactive material located between the electrodes, wherein the electroactive material comprises a plurality of particle cores, each particle core surrounded by a polymer covering having one or more strands of an elastomeric polymer, wherein:
one or more of said strands are chemically bonded to the particle core; and
the layer is bound in a manner that enables a layer thickness to respond to application of a voltage differential between the first and second electrodes.
22. The invention of claim 21 , wherein said thickness decreases in response to said voltage application.