A soft dielectric polymer, plasticized poly(vinyl chloride) (PVC gel), has been known as a characteristic actuator with electrotactic creep deformation. The deformation can be applied for bending and contraction. The mechanism of the deformation has been attributed to the colossal dielectric constant of the gel induced by dc field. The dielectric constant at 1 Hz, jumps from less than10 to thousand times larger value. The huge dielectric constant suggests the gel can have electro-optic function. In this paper, we introduce the gel can bend light direction by applying a dc electric field. The PVC gel can bend light direction depending on the electric field. Detailed feature of the light bending will be introduced and discussed. Bending angle can be controlled by dielectric plasticizer and electric field. The components of the gel, PVC and plasticizer themselves, did not show any effect of electro-optical function like the PVC gel. The same feature can be observed in other polymer, like poly(vinyl alcohol)-dimethyl sulphoxide gel, too.
Poly(vinyl chloride) (PVC) plasticized with large amount of plasticizer has been investigated as a material for artificial muscle or actuator that can be actuated by applying an electric field. This material shows "creep deformation" on an electrode. The deformation looks like a pseudopodial deformation of amoeba. The deformation can be utilized for swift bending motility. In this paper, we investigated the mechanism of the creep deformation. Microscopic Raman spectroscopy revealed that the orientation of polymer network or plasticizer molecule was hardly detectable under the experimental conditions employed for the electrical actuation. Orientation of plasticizer was detected only slightly at higher field application. Small angle X-ray scattering analysis clarified that the PVC gel (plasticized PVC) sustains network structure even at the very high plasticizer content like 90wt%. With the increase of plasticizer content, space distance increased linearly, implying the network structure is sustained. This nature of the PVC gel plays a critical roll in the elastic creep deformation. The network structure of the gel depends on the chemical nature of the plasticizer itself. When the increase of plasticizer content caused serious deterioration of the physical network of PVC polymer chain, the PVC gel only deformed irreversibly by creep. The bending deformation also investigated from the viewpoint of electrode asymmetry. The results suggest effective charge injection and the charge concentration on the electrode is the controlling factor of this amoeba-like deformation.
Non-ionic dielectric polymers have not been considered adequate for electroactive actuator materials because of their poor reaction to the electric field. As electroactive polymeric materials, the polyelectrolytes and conductive polymers have been investigated intensively, since they can show large deformation in aqueous media or in the presence of water as an additive. In this paper, the author will show the non-ionic polymeric materials can be used as electrically active materials. The electrically induced deformation phenomena that will be shown are contraction and relaxation, bending by solvent drag in the gel, crawling deformation, and "electrotactic" amoeba-like creep deformation. And the controlling factors of bending of elatomers. The materials that will be treated in this presentation covers from highly swollen dielectric gels through plasticized polymers to non-solvent type elastomers. Characteristics of the actuations are particularly large deformation or huge strain under much smaller energy dissipation compared to the conventional polyelectrolyte or conductive polymer actuators. Applications of the materials for pumping, valve, artificial pupil etc. will be demonstrated.
Various type of non-ionic soft polymer materials from polymer gel to elastomers were actuated in efficient and remarkable manners by applying an electric field. The polymer gel swollen with large amount of dielectric solvent showed not only remarkable contraction and relaxation in the direction of the field, but also huge bending deformation within dozens of milliseconds. Molecular orientation of solvent did not play a critical role in the bending deformation,
but a solvent drag induced by the field was the origin of an asymmetric pressure distribution which bended the gel. In the case of plasticized polymer, the solvent (or plasticizer) drag was difficult and negligibly small. However, we found a reversible creep deformation of the plasticized polymer. The deformation only occurred on the electrode surface. The strain induced could have reached over 300%. The sample was stable over 2 years. This creep deformation was
successfully applied in bending of 100 degree per 30 milli-second under the current of nano-ampere range. Non-ionic polyurethane elastomers, which contained neither solvents nor plasticizers, could also be electrically bended, and the deformation was controlled systematically by changing chemical structures. The bending deformation showed memory effect, and the direction of the bending was chemically controllable. It was suggested that an asymmetric space charge distribution in the polymer film plays a critical role in the bending deformation. The concept presented through these
works will be a guide to a novel type of electrically active dielectric-soft-polymer actuator or a kind of artificial muscles.
We have reported that nonionic gel of ploy(vinyl alcohol) (PVA) swollen with dimethyl sulfoxide (DMSO) responds to an electric field rapidly with a large and reversible deformation, which includes a spherical bending motion to the anode side and a contraction in the direction of an electric field. The electrically induced strain in the polymer gel has ben suggested to be due to electrically induced unidirectional movement of solvent in the gel. The chemically crosslinked polymer gels used here, which had only about 2wt% of polymer content and far much larger amount of solvent in the gel networks, were a good elastic body to suffer a large mechanical deformation. Here, we discussed mechanical properties of the gel under and out of the application of an electric field, and also the interaction between the polymer network and solvent. The electrically induced deformation was discussed, as well, on the proportionality of strain to the square of an electric field for both of the bending motion to the anode side and the contracting motion in the field direction. Furthermore, we drove out the electrically induced solvent force in the gel under various conditions, and demonstrated that the electroactive non-ionic gel can be used in some mechanical devices.
Non-ionic polymer gel was found to bend and scrawl much faster than conventional polymer gels by applying d.c. electric field. The motion looks like to be an action of a biological muscle in a sense. The dimensions of the gel were 2 mm in thickness, and 7 X 5 mm2 in area. Both surface of the gel sheet was coated with thin gold film whose thickness is 0.1 (mu) . Bending angle reaches 180 degrees within 90 ms when electric field of 500 V/mm was applied. The current was around 0.03 mA under the field, suggesting that the heat generated in the motion be negligible. The gel was composed of chemically crosslinked poly(vinyl alcohol) (PVA) swollen with dimethyl sulfoxide (DMSO). Solvent loss from the gel in the action was negligible. DMSO orientation by an electric field was investigated by Raman spectroscopy. DMSO was found to flow or to generate a pressure gap under an electric field over 60 V/mm. It turned out that the orientation of DMSO does not directly induce the motion of a gel, but the electrically induced DMSO flow plays a critical role in the actuation. The electrically induced solvent flow implied that the solvent was enforced to flow from an anode side to a cathode side. The results are consistent to the observation of the bending or scrawling motion in which the cathode side is expanded much more than the anode side. As a conclusion, the concept of the 'electrically-induced solvent-drag' gel actuator provides the most promising way to a high power artificial muscle, a soft actuator, at this moment.