MOEMS micromirror arrays in smart windows for daylight steering

Abstract

Micro-opto-electro-mechanical systems (MOEMS) micromirror and shutter arrays have gained huge interest in research and applications. Our study starts with an overview on the technological achievements and experimental results of groups that have been working on this field. The main part of our study is revealing the MOEMS micromirror array technology for light steering via smart glazing for buildings. The mirror array is actuated electrostatically and integrated between the panes of insulation glazing. Depending on user activity as well as daytime and season requirements, the MOEMS micromirror arrays shall enable personalized light steering, energy saving, and reduction of CO 2 emission. Technological fabrication of subfield addressing up to 64 fields inside the arrays is presented. Experimental characterization results such as actuation voltages, maximum and minimum transmission, contrast, and energy saving potential are reported. Using an industrial window module fabrication process, a laboratory demonstrator and a function demonstrator have been implemented. Rapid aging tests including vibrations, extreme temperatures, multiple temperature cycles, and long-term electrostatic actuation of micromirror structure were performed to evaluate reliability and lifetime. These results validate extrapolated lifetimes-in future applications as active windows-far beyond 40 years, as well as their robustness during transportation, installation, and against all vibration influences in buildings. © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

A novel approach to construct self-assembled 3D MEMS arrays

“…The shutters will curl back to their initial configuration when the applied voltage is reduced to a certain threshold. This behavior is already well known from our micromirror elements (Hillmer et al 2018(Hillmer et al , 2021Iskhandar et al 2019). In the case of the asymmetric hollow cylinders reported here, the paired micro shutters could not be separated again-even with massive electrostatic actuation (100 V).…”

“…Microelectromechanical systems (MEMS) for light processing have been studied for various applications. Among others, micromirror array-based MEMS have been reported for (1) NxN switches in wavelength division multiplexing (Chuan Pu et al 2000;Lin and Goldstein 2002;Aksyuk et al 2003), (2) for beamers (Duncan et al 2002;Ballard et al 2016) and (3) for light steering via smart glazing in buildings (Hillmer et al 2018(Hillmer et al , 2021Iskhandar et al 2019). In adaptive optics, deformable mirrors were developed, providing high-order correction of optical aberrations used in astronomy, laser micromachining, maskless lithography, microscopy medical technology, and optical free-space communication (Bifano 2011;Manzanera et al 2011).…”

Grating optical filter with angular-selective transmission for smart windows

“…This technology has (i) a higher actuation speed and greater operating temperature range and color neutrality compared with electrochromic systems, (ii) wind insensitivity in contrast to external active Sun blinds, (iii) low energy consumption compared with all other systems, and (iv) lack of window heating, unlike absorption systems. 41 Various types of optical filters with an angular selectivity of transmittance or reflection are being explored, but they are intended for purposes other than filtering solar radiation in windows. [42][43][44][45] This paper presents new research results on a double-grating optical filter 46,47 with angularselective directional light transmission.…”

Design and Analysis of LCD-Based Modulator for Passive Sunlight Communications

“…There are two main light controlling categories known as MEMS-based micro-shutters and Electrolyte-based devices, which includes electrochromic devices (ECDs), suspended particle devices (SPDs) and liquid crystal devices (LCDs). Smart glass is usually utilized for daylight shading and steering by absorbing or scattering the light to control its transmission or deflect it in certain directions to illuminate specific areas [6]. Nevertheless, it is not commonly used for wireless communication purposes mainly due to its long switching times.…”

“…In particular, ECDs and SPDs are not suitable for such application as their performances need to be further optimized in terms of speed and contrast [3], [7], [8]. On the other hand, MEMS-based micro-shutters provide short switching times and high contrast, but they can be energy inefficient and they are still in research stage [6], [9], [10] . Meanwhile, LCDs offer high contrast and rapid speed making it adequate for the target applications [11].…”