We report on new method to obtain micrometric electroactive polymer actuators operating in air. High speed conducting
Interpenetrating Polymer Network (IPN) microactuators are synthesized and fully characterized. The IPN architecture
used in this work allows solving the interface and adhesion problems, which have been reported in the design of classical
conducting polymer-based actuators. We demonstrated that it is possible to reduce the thickness of these actuators by a
specific synthetic pathway. IPN host matrixes based on polyethylene oxide / polytetrahydrofurane have been shaped by
hot pressing. Then, the resulting thin host matrixes (below 10 μm) are compatible with the microfabrication
technologies. After interpenetration of poly(3,4-ethylenedioxythiophene) (PEDOT), these electroactive materials are
micro-sized using dry etching process. Frequency responses and displacement have been characterized by scanning
electronic microscopy. These conducting IPN microactuators can be considered as potential candidates in numerous low
frequency applications, including micro-valves, micro-optical instrumentation and micro-robotics.
In recent years, many studies on electroactive polymer (EAP) actuators have been reported. One promising technology is
the elaboration of electronic conducting polymers based actuators with Interpenetrating Polymer Networks (IPNs)
architecture. Their many advantageous properties as low working voltage, light weight and high lifetime (several million
cycles) make them very attractive for various applications including robotics. Our laboratory recently synthesized new
conducting IPN actuators based on high molecular Nitrile Butadiene Rubber, poly(ethylene oxide) derivative and
poly(3,4-ethylenedioxithiophene). The presence of the elastomer greatly improves the actuator performances such as
mechanical resistance and output force. In this article we present the IPN and actuator synthesis, characterizations and
design allowing their integration in a biomimetic vision system.
A promising alternative of multi-layered devices showing electrochromic properties results from the
design of a self-supported semi-interpenetrating polymer network (semi-IPN) including an electronic conductive
polymer (ECP) formed within. The formation of the ECP in the network has already been described by oxidative
polymerization using iron trichloride as an oxidant and leading to conducting semi-IPN with mixed electronic
and ionic conductivities as well as convenient mechanical properties. This presentation relates to the elaboration
of such semi-IPN using polyethyleneoxide (PEO) network or a PEO/NBR (Nitrile Butadiene Rubber) IPN in
which a linear poly (3,4-ethylenedioxythiophene) (PEDOT) is formed symmetrically and selectively as very thin
layers very next to the two main faces of the film matrix. PEO/PEDOT semi-IPNs lead to interesting optical
reflective properties in the IR between 0.8 and 25 μm. Reflectance contrasts up to 35 % is observed when, after
swelling in an ionic liquid, a low voltage is applied between the two main faces of the film. However the low
flexibility and brittleness of the film and a slow degradation in air at temperature up from 60°C prompted to
replace the PEO matrix by a flexible PEO/NBR IPN one. Indeed, the combination of NBR and PEO in an IPN
leads to materials possessing flexible properties, good ionic conductivity at 25°C as well as a better resistance to
thermal ageing. Finally, NBR/PEO/PEDOT semi-IPNs allow observing comparable reflectance contrast in the
IR range than those shown by PEO/PEDOT semi-IPNs.
This paper presents a new way to design and fabricate ionic polymer actuators showing a linear movement in air. This is done by use of an original shaping during the polymerization step. The possible solutions for linear actuation were tested with a simulation technique that has been designed on purpose, which helped us to choose the best. By means of very unusual fabrication techniques that were required for that, actuators were made following this principle and their performances were measured.
In order to solve the interface and adhesion problems encountered with multilayered actuators, IPN based actuators are presented. The IPNs are synthesized between poly(ethylene oxide) and polybutadiene networks in which the conducting polymer (poly(3,4-ethylenedioxythiophene)), PEDOT, is gradually dispersed i.e. the content decreases from the outside towards the center of the film. The conducting IPN morphology was investigated by DMA and microscopy. The choice of the solid polymer electrolyte system is critical when operating in air. Aqueous solution or organic solvents containing electrolytes were first used, but drying failure could not be prevented. The most promising results are obtained with a room temperature ionic liquid, 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide (EMITFSI). During the redox reactions involving PEDOT in EMITFSI, a cation transfer mechanism occurred. Moreover, the bis-(trifluoromethylsulfonyl)imide anion behaves as a plasticizing agent for the IPN matrix. We observed that no degradation of the conducting polymer and no drying process occurred during period as long as 3 months. These actuators can achieve more than 7 E6 bendings from 1 to 18 Hz under applied potential from 2 to 5 V
A new approach is proposed, namely the use of Interpenetrating Polymer Networks (IPNs) in order to solve the interface and adhesion problems in the design of classical conducting polymer based actuators. Semi IPN type materials are synthesized between poly(3,4-ethylenedioxythiophene) and a poly(ethyleneoxide) based network as the ionic conducting partner. The synthetic pathway which will be presented ensures a gradual dispersion of the electronic conducting polymer through the thickness of the material i.e. the content decreases from the outside towards the center of the film. The system is thus similar to a layered one with the advantage that the intimate combination of the two polymers needs no adhesive interface. The influence of the morphology and chemical composition of the matrix on the electronic conductivity of the material have been studied. The surface conductivity can reach 15 S/cm. Finally, this material is capable of a 45 degree(s) angular deflexion under a 0.5 V potential difference.
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