Tunable, optical microcavities (MC) gain more and more importance for display, laser or other optical applications. The setup of dielectric elastomer actuators (DEA) enables a simple integration of an optical cavity, since reflective electrodes can confine a cavity that is filled with a transparent elastomer. Applying a voltage to the electrodes leads to squeezing of the elastomer and, due to the cavity thickness decrease, the resonator modes of interfering light changes. In this work we present an electrically tunable, optical MC based on ultra-soft poly(dimethylsiloxane) (PDMS). The PDMS gel is coated on a glass substrate with a distributed Bragg reflector, an ITO bottom electrode and a flexible, highly reflective metal electrode and mirror on top. The usage of an ultra-soft PDMS gel, with a storage modulus of about 1kPa, allows to decrease the operating voltage down to a few hundred or even several ten volts. The critical step of fabrication is the metallization of the PDMS gel layer that requires a previous oxidizing surface activation to gain reflective and conductive silver based layers on top. Therefore, the effects of oxygen plasma and UV/ozone treatment on PDMS and the created metal layer were investigated intensively. The performance of the electrically tunable, optical MC is tremendously dependent from an adequate surface activation and structuring of the top electrodes considering the mirror displacement and activation voltage. Here we could show that tunable MCs based on oxygen plasma activated PDMS show a homogenous and high thickness decrease up to 70% at 200V.
KEYWORDS: Actuators, Polymers, Microelectromechanical systems, Control systems, Visualization, Information visualization, Bioalcohols, Polymerization, Ultraviolet radiation, Video
Here we introduce a high-resolution tactile display based on the integration of 4,320 actuators with a density of about
300 actuators per cm2 into an array displaying both visual and tactile information. The actuators are fabricated
simultaneously by UV-patterning. Intrinsically active polymers called "smart hydrogels" are used as actuators which are
sensitive to changes in temperature. The high resolution temperature field is controlled by a computer using an optical
interface that is controlled by a computer. Thus the temperature is adjusted for each actuator and it can be independently
controlled. An actuator pixel changes color from transparent to opaque providing a visual monochrome functionality.
The altitude and the elasticity change as well. Therefore the tactile display is able to generate artificial impressions about
contours, textures, profiles and the softness of a surface. The actuators are covered by a thin foil equipped with knobs,
which can additionally vary the tactile impressions. For fabrication an inexpensive modified dry photoresist technology
was used for the masters of up to (200 × 155) mm2. This device demonstrates a high integration into MEMS with a
monolithically fabricated actuator array of temperature-sensitive active polymer and an optoelectronic control.
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