Dielectric elastomer actuators (DEA) are smart lightweight flexible materials integrating actuation, sensing, and structural functions. The field of DEAs has been progressing rapidly, with actuation strains of over 300% reported, and many application concepts demonstrated. However many DEAs are slow, exhibit large viscoelastic drift, and have short lifetimes, due principally to the use of acrylic elastomer membranes and carbon grease electrodes applied by hand. We present here a DEA-driven tuneable lens, the world's fastest capable of holding a stable focal length. By using low-loss silicone elastomers rather than acrylics, we obtain a settling time shorter than 175 μs for a 20% change in focal length. The silicone-based lenses show a bandwidth 3 orders of magnitude higher compared to lenses of the same geometry fabricated from the acrylic elastomer. Our stretchable electrodes, a carbon black and silicone composite, are precisely patterned by pad-printing and subsequently cross-linked, enabling strong adhesion to the elastomer and excellent resistance to abrasion. The lenses operated for over 400 million cycles without degradation, and showed no change after more than two years of storage. This lens demonstrates the unmatched combination of strain, speed and stability that DEAs can achieve, paving the way for complex fast soft machines.

We report on miniature dielectric elastomer actuators (DEAs) operating in zipping mode with an analytical model that predicts their behavior. Electrostatic zipping is a well-known mechanism in silicon MEMS to obtain large deformations and forces at lower voltages than for parallel plate electrostatic actuation. We extend this concept to DEAs, which allows us to obtain much larger out-ofplane displacements compared to silicon thanks to the softness of the elastomer membrane. We study experimentally the effect of sidewall angles and elastomer prestretch on 2.3 mm diameter actuators with PDMS membranes. With 15° and 22.5° sidewall angles, the devices zip in a bistable manner down 300 μm to the bottom of the chambers. The highly tunable bistable behavior is controllable by both chamber geometry and membrane parameters. Other specific characteristics of zipping DEAs include well-controlled deflected shape, tunable displacement versus voltage characteristics to virtually any shape, including multi-stable modes, sealing of embedded holes or channels for valving action and the reduction of the operating voltage. These properties make zipping DEAs an excellent candidate for applications such as integrated microfluidics actuators or Braille displays. Abstract. We report on miniature Dielectric Elastomer Actuators (DEAs) operating in zipping mode with an analytical model that predicts their behavior. Electrostatic zipping is a well-known mechanism in silicon MEMS to obtain large deformations and forces at lower voltages than for parallel plate electrostatic actuation. We extend this concept to DEAs, which allows us to obtain much larger out-of-plane displacements compared to silicon thanks to the softness of the elastomer membrane. We study experimentally the e↵ect of sidewalls angle and elastomer prestretch on 2.3 mm diameter actuators with PDMS membranes. With 15 and 22.5 sidewalls angle, the devices zip in a bistable manner down 300 µm to the bottom of the chambers. The highly tunable bistable behavior is controllable by both chamber geometry and membrane parameters. Other specific characteristics of zipping DEAs include well-controlled deflected shape, tunable displacement vs. voltage characteristic to virtually any shape including multi-stable modes, sealing of embedded holes or channels for valving action and reduction of the operating voltage. These properties make zipping DEAs an excellent candidate for applications like integrated microfluidics actuators or Braille displays. Reference

We report on the use of zipping actuation applied to dielectric elastomer actuators to microfabricate mm-sized pumps. The zipping actuators presented here use electrostatic attraction to deform an elastomeric membrane by pulling it into contact with a rigid counter electrode. We present several actuation schemes using either conventional DEA actuation, zipping, or a combination of both in order to realize microfluidic devices. A zipping design in which the electric field is applied across the elastomer membrane was explored theoretically and experimentally. Single zipping chambers and a micropump body made of a three chambers connected by an embedded channel were wet-etched into a silicon wafer and subsequently covered by a gold-implanted silicone membrane. We measured static deflections of up to on chambers with square openings of 1.8 and 2.6 mm side, in very good agreement with our model.

The analytical formulas describing the behaviour of dielectric elastomer actuators (DEAs) are based on hyperelastic strain energy density functions. The analytical modelling of a DEA will only lead to meaningful results if the dielectric elastomer can be accurately represented by the chosen hyperelastic model and if its parameters are carefully matched to the elastomer. In the case of silicone elastomers, we show that the strain energy density of a thin elastomeric membrane depends on the maximum deformation the membrane was previously submitted to (Mullins effect). We also show that using model parameters coming from an uniaxial pull-test to predict the behaviour of the elastomer in an equi-biaxial configuration leads to erroneous results. We have therefore built a measurement setup, which allows testing thin elastomeric membranes under equi-biaxial stress by inflating them with a pressure source. When modelling a DEA under equi-biaxial stretch, the measurement data can be used directly, without the need of an hyperelastic model, leading to voltage-stretch prediction closer the the measured stress-stretch behaviour of the dielectric membrane.

We demonstrate here an alternative dielectric elastomer actuator (DEA) structure, which relies on the compliant nature of elastomer membranes but does not require any electric field in the elastomer. Our elastomer zipping device is a macroscopic version of the electrostatic zipping actuators common in silicon MEMS. It consists of a cm-sized metallic bottom electrode, covered by a thin insulator, on which the elastomer membrane is bonded, enclosing a tapered air gap. A compliant electrode is patterned on the lower face of the elastomer membrane. Applying a voltage between solid bottom electrode and compliant electrode leads to controlled pull-in in movement, comparable to the closing of a zipper, thus giving large strokes and forces with no electrical requirements on the elastomer since no voltage is applied across the membrane. The compliant electrodes (20 mm diameter) are produced by metal ion-implantation into the elastomer membranes. The bottom metal electrodes are coated with 10 to 30 µm of Al 2 O 3 . We report on our experimental study of membrane deflection and dynamics and discuss the effect of design parameters such as elastomer mechanical properties and actuator geometry. Membrane deflection of up to 1.4 mm was reached at only 200 V actuation voltage. The large membrane deformation achieved with this zipping actuation can be applied to applications such as pumps or tunable liquid lenses. The out-of plane movement of the membrane can be used for linear actuation.