This paper presents a principle to develop multi‐function dielectric elastomer actuators (DEAs) that can concurrently accomplish linear actuation and sound generation through a single electrical input. A centimeter‐scale cone‐shaped DEA is fabricated using silicone‐based dielectric and electrodes. Measurements of the vibro‐acoustic response reveal that the pumping deformation of the DEA contributes to a negligible extent in the sound generation, which is hence ascribable to higher order structural modes whose frequency pass‐band is highly uncoupled from that of the pumping mode. Exciting the DEA with a multi‐chromatic input voltage allows achieving strokes close to 1 mm or blocking forces over 0.5 N, while simultaneously generating sound pressure levels over 60 dB, regardless of possible forces and/or mechanical constraints on the DEA pumping motion. The ability of the DEA to concurrently generate linear actuation and sound is demonstrated via proof‐of‐concept tests: the DEA can reproduce music, while at the same time generating a deformation pulse or lifting a load comparable with its own blocking force. Furthermore, measuring the current generated by the DEA allows detecting deformations impressed by the exterior and use the DEA as an active audio‐tactile interface, which produces a combined vibro‐acoustic stimulus in response to a user's touch.

This paper presents a concept of a dielectric elastomer actuator (DEA) user interface (smart button) that can sense a user’s touch and provide multi-sensory tactile and acoustic feedbacks through a single electrical input signal. The DEA relies on a multi-layer layout, in which a layer detects user-driven deformations (touches) via custom-built capacitance sensing electronics, and the remaining layers are used to provide actuation (audio-tactile feedbacks). Building upon a recently presented principle, combined tactile and acoustic feedbacks are produced by concurrently exciting different vibration modes of the same active membrane over different frequency ranges. An integrated demonstrator setup is presented, which includes a DEA, an acoustic enclosure, compact sensing and driving electronics. A characterization of the prototype is conducted, including an analysis of the sound pressure level, the force/stroke output at lower working frequencies, the ability to sense deformations with different profiles and produce combined audio-tactile outputs. Compared to previous works on multi-function DEAs, the system presented in this paper provides largely improved sensing performance (with lower working voltage) and features a deeper level of integration (with small-scale custom sensing electronics, and logics embedded onto scalable microcontrollers) and is thus specifically optimised for user-interaction applications. On this end, tests with users are presented here for the first time, which allowed evaluating the subjective perception of the interface’s feedbacks. By means of further optimisation and miniaturisation of the power/sensing electronics and structural components, the layout and multifunction DEA principle presented here might lead, in the future, to the development of DEA-based smart buttons for active surfaces, or portable/wearable user interfaces and communicators.

When dielectric elastomer actuators (DEAs) are actuated via high voltage, their electrical capacitance changes according to the geometry. Therefore, displacement of the actuator can be correlated to the change in capacitance, thus opening up the possibility of self-sensing DEA devices. Self-sensing can be exploited to achieve a sensorless closed loop DEA system, which is attractive from size, weight, and cost perspectives. This research work presents an embedded control system, which enables self-sensing closed loop position control of a DEA. The proposed architecture is cost effective, compact in size, easy to integrate as well as to reprogram in comparison to previous self-sensing implementations relying on FPGA systems. In the developed setup, the online self-sensing algorithm is used for estimation of displacement in a spring-biased strip DEA. For this system, understanding and mapping the correlation between estimated capacitance, applied voltage, and resulting displacement is essential for achieving an accurate DEA position reconstruction. An experimental setup is developed, and used to test a spring-biased DEA system. Self-sensing based feedback control is then used to achieve a tight regulation of the actuator displacement. To verify the effectiveness of the sensorless closed loop control system, its performance is finally compared to sensor-based feedback architectures.

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