In this paper, we develop and characterise the use of amorphous Silicon as an optically functional material in actuated devices. A novel actuator is developed which uses thin amorphous silicon film deposited on a polyimide substrate using Plasma Enhanced Chemical Vapour Deposition (PECVD). The actuator generates an active stroke via electrostatic attraction which causes the electrodes to “zip” together. The magnitude of displacement is controlled by exploiting the light-dependant resistance of an amorphous silicon (a-Si) photoreceptor integrated onto the actuator. An 8mm long actuator was prototyped and curvature changes were measured using image processing techniques to track the amorphous silicon electrode during actuation. A change of radius of 1mm was found between the ambient (22 Lux) and illuminated states (36 kLux) with an applied voltage of 5 kV.
Holographic Acoustic Tweezers can trap and manipulate multiple particles individually using acoustic radiation forces. This technology is similar to the well-established Holographic Optical Tweezers but presents some notable differences. For instance, acoustic tweezers can operate on particles ranging from the micrometre to the centimetre scales. The particles can be made of a wide range of materials such as gases, liquids, metals, plastics or even living things. The propagation media can be air, water and does not need to be optically transparent, therefore manipulations inside the human body from the exterior are a possibility. These unique features enable multiple applications such as acoustophoretic displays in which several particles or one fast-moving particle form objects in mid-air. On the other hand, tiny quirurgic instruments that are inserted in the body could be controlled not only in position but also in orientation due to the multiple trapping point capabilities.
Optically-switched composite materials based on semiconducting materials have the potential to simplify the circuitry required to control artificial muscles. This contactless control method has the potential to improve visual technologies by enabling controllable haptic and morphing interfaces. Optically-switched active displays could provide enhanced user interaction, especially for those with visual impairments. Research into morphing interfaces with dielectric elastomer actuators (DEAs) centralizes on segmented electrode architectures that can achieve large active strains in multiple degrees of freedom. However, controlling the activation of multiple electrodes typically requires an array of discrete rigid components (e.g. MOSFETs) as well as the separation of high-voltage power lines and low-voltage control signals. In this work, we develop a photo-switched DEA system that removes the need for wired control signals, reducing complexity. Photonic switching of DEA electrodes is achieved by exploiting the light-dependent resistance of a thin film of deposited amorphous silicon (a-Si). Samples with layer thicknesses of 0.84 μm have been fabricated using plasma enhanced chemical vapor deposition. Breakdown voltages of above 6kV were obtained when using a nonconducting substrate (glass). Preliminary testing of the system shows that voltage swings of up to 865V can be achieved between ambient and direct illumination, producing an out of plane actuation of 2 μm in a weight-biased DEA disc actuator. Further tuning of the electric circuit should lead to larger actuation strains. Future work will focus on the control of multiple DEA electrodes using localized light patterns as well as testing and characterizing other materials to improve the voltage swing across the DEA.
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