Abstract
Ionic electromechanically active capacitive laminates are a type of smart material that move in response to electrical stimulation. Due to the soft, compliant and biomimetic nature of this deformation, actuators made of the laminate have received increasing interest in soft robotics and (bio)medical applications. However, methods to easily fabricate the active material in large (even industrial) quantities and with a high batch-to-batch and within-batch repeatability are needed to transfer the knowledge from laboratory to industry. This protocol describes a simple, industrially scalable and reproducible method for the fabrication of ionic carbon-based electromechanically active capacitive laminates and the preparation of actuators made thereof. The inclusion of a passive and chemically inert (insoluble) middle layer (e.g., a textile-reinforced polymer network or microporous Teflon) distinguishes the method from others. The protocol is divided into five steps: membrane preparation, electrode preparation, current collector attachment, cutting and shaping, and actuation. Following the protocol results in an active material that can, for example, compliantly grasp and hold a randomly shaped object as demonstrated in the article.
Highlights
Ionic electromechanically active polymer or polymeric composites are intrinsically soft and compliant materials that have received increasing interest in different soft robotics and biomimetic applications
Ionic electromechanically active polymer or polymeric actuators are typically made of two- or three-layer laminar composites and bend in response to electrical stimulation in the range of few volts (Figure 1). This bending motion is caused by the swelling and contraction effects in the electrode layers, and it is typically brought along either by faradaic reactions on the electrodes (e.g., in case of electromechanically active polymers (EAPs) like the conductive polymers) or by capacitive charging of the double-layer. In this protocol (Figure 2), we focus on the latter; we show the fabrication of an electromechanically active composite that consists of two high specific surface area electronically conductive carbon-based electrodes that are separated by an inert ion-conductive membrane that facilitates the movement of cations and anions between the electrodes – a configuration very similar to the supercapacitors
In case of material characterization, it is impossible to distinguish between currents stemming from the electroactive material and that stemming from the electrochemical activity of copper[29]
Summary
Ionic electromechanically active polymer or polymeric composites are intrinsically soft and compliant materials that have received increasing interest in different soft robotics and biomimetic applications (e.g., as actuators, grippers, or bioinspired robots[1,2]). Commercial ionomeric membranes (e.g., Nafion) tend to swell and buckle significantly in response to solvents used in the later manufacturing steps[12], and some polymers (e.g., cellulose23) are known to dissolve to some extent in some ionic liquids, possibly causing problems with the repeatability of the fabrication process and resulting in poor uniformity of the electrodes This protocol focuses on actuators with an integral passive and chemically inert component in the membrane (e.g., glass fiber or silk with PVDF or PTFE) that stops the composite from swelling and buckling in later fabrication steps or from forming short-circuit hotspots. Prevent direct skin contact with the final composite (unless it is encapsulated28) by always wearing gloves
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