Animals make use of soft tissues and muscles to produce fluidic motion with superior deformability and adaptability. Soft robotics focuses on mimicking these natural soft systems to produce similar motion. Common approaches to achieve actuation in soft robotics are pneumatics, fluidics, shape memory materials, magnetic fields, chemical reactions and electroactive polymers (EAPs). EAPs are particularly interesting due to their high efficiencies, lightweight design and superior structural compliance. Dielectric elastomer actuators (DEAs), an EAP, can produce large strains, low cost and complexity of fabrication. Performance of a DEA depends on intrinsic material properties like relative permittivity and Young’s modulus. Conventional approaches to manipulate either of these material properties have made use of solid fillers, chemical additives and modifications of polymer backbone, and are generally accompanied with undesirable effects on other properties. In the present work, we demonstrate the fabrication of self-contained liquid filler-polymer composite, with synergetic effects on electrical and mechanical properties of the resulting matrix. A high-k, non-reactive liquid filler was hand mixed with PDMS (polydimethylsiloxane). These composites show an increase of 2 times in the relative permittivity (dielectric constant) and softening of the matrix (more than 50 times decrease in the Young’s modulus), compared to the pristine polymer. The composites can be actuated without pre-stretch with visibly detectable deformations and the figure of merit for electro-mechanical performance was calculated at an impressive value of 94. These ultra-soft composites can be used for applications such as soft robotics, optoelectronics and wearable electronics.
With the focus on providing a sense of touch in robots, enabling feedback in virtual reality (VR) and augmented reality (AR) environment, telerobotics, remote sensing and improving user experience with touch sensitive devices like display kiosks and smartphones, haptic interfaces have become critical as they can convey information quickly. A human hand can feel different physical parameters such as roughness, softness and vibration and discern them as textures of the surface. Most of the technologies being employed for haptic feedback currently rely on simulating the perception of texture change, however few of the technologies like microfluidics and electroactive polymers (EAPs) can create actual topographical changes on the surface. Additionally, most of these haptic devices are opaque and they often serve as mere touchpads whilst the visual component of the simulation is projected elsewhere, so the user appears to interact with the simulated object indirectly. Dielectric elastomer actuators (DEAs), an EAP, is of peculiar interest owing to their characteristics like large actuation strains, facile fabrication, low costs of manufacturing and low power consumption. Herein, we demonstrate a large area, transparent tactile feedback device with 4 individually controlled active regions, that can be integrated onto electronic displays to provide unobstructed topographic texture change. We fabricate the device in a unique architecture, with the elastomeric layer, compliant electrodes, and the soft passive layer as all transparent materials. These devices show high transparency of over 70% in the visible region of the spectrum, and surface deformation of ~165 μm.
Tactile feedback devices and microfluidic devices have huge significance in strengthening the area of robotics, human machine interaction and low cost healthcare. Dielectric Elastomer Actuators (DEAs) are an attractive alternative for both the areas; offering the advantage of low cost and simplistic fabrication in addition to the high actuation strains. The inplane deformations produced by the DEAs can be used to produce out-of-plane deformations by what is known as the thickness mode actuation of DEAs. The thickness mode actuation is achieved by adhering a soft passive layer to the DEA. This enables a wide area of applications in tactile applications without the need of complex systems and multiple actuators.
But the thickness mode actuation has not been explored enough to understand how the deformations can be improved without altering the material properties; which is often accompanied with increased cost and a trade off with other closely associated material properties. We have shown the effect of dimensions of active region and non-active region in manipulating the out-of-plane deformation. Making use of this, we have been able to demonstrate large area devices and complex patterns on the passive top layer for the surface texture change on-demand applications. We have also been able to demonstrate on-demand microfluidic channels and micro-chambers without the need of actually fabricating the channels; which is a cost incurring and cumbersome process.