Abstract
Electrowetting retroreflectors use a simple and scalable construction, and incorporate an electrically tunable liquid lenslet. By electrically modulating the lenslet geometry, the reflection is switched between retroreflection and scattering. In this paper, we report new capability and characterization, including higher index liquids and contrast ratio as a function of contact angle (theta(V)). The reflected intensity is also spatially profiled and reported as a function of view angle. A high contrast ratio of >16X is demonstrated, and methods for further improving performance are discussed. Because the electrowetting retroreflector platform is broad spectrum (VIS-IR), the electrowetting retroreflector may be useful for a large variety of naked eye applications such as safety markings, road-signage, or friend-foe-identification.
Highlights
Retroreflectors reflect light back in the same direction as the light coming from the illumination source [1]
By electrically modulating the lenslet geometry, the reflection is switched between retroreflection and scattering
We report new capability and characterization, including higher index liquids and contrast ratio as a function of contact angle
Summary
Retroreflectors reflect light back in the same direction as the light coming from the illumination source [1] They have numerous applications such as road signs, safety markers, ranging, and surveying [2]. Switchable retroreflectors [3, 4] have been demonstrated for free-space communications. These prior approaches utilize microelectromechanical or multiple-quantum well modulation. We recently reported in a letter [5] an altogether different switchable retroreflector approach that uses a classical corner-cube geometry microreplicated in a polymer substrate. This work provides further insight into the performance and behavior of electrowetting retroreflectors for naked eye applications such as safety markings, road-signage, or friend-foe-identification
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