Analog-controlled light microshutters based on electrothermal actuation for smart windows

Smart windows for sunlight control play an important role in modern green buildings. Electrically-controllable light microshutters provide a promising solution for smart windows. However, most of reported microshutters work under on/off binary mode. In this work, an electrothermally actuated microshutter that can achieve analog light control is proposed. The microshutter consists of an array of electrothermal Al/SiO2 bimorph cantilever plates suspended over a through-silicon cavity. The device is fabricated by a combination of surface- and bulkmicromachining processes. Test experiments show that for a single microshutter pixel, the device opening ratio can be tuned continuously from 78.6% (Open state, 0 V) all the way down to nearly 0% (Close state, 8 V) with a small hysteresis. For the entire array of 2 × 5 microshutters, the light transmission ratio varies continuously from 63.3% to 3.6% when the applied voltage is increased from 0 to 7.3 V. Furthermore, the response time, long-term reliability and window-like function of the microshutter are tested.