Emerging MEMS technologies such as electrostatic and field-effect actuators drive innovation in the fields of haptics, adaptive optics and reconfigurable microfluidics. For those applications, a large number of individually addressed actuators, typically in an array format, are required. However, these actuators need high voltages, and while architectures for control of low-voltage arrays are readily available and can be easily implemented in microelectronics, solutions for control of high-voltage arrays are lacking.  Existing solutions rely on individual wiring of each actuator to a single off-chip high-voltage switch [1-3]. Although this approach can be useful for small arrays, it leads to large and bulky control units that are not scalable to large arrays.

In this article, we report on an alternate approach that uses light to individually address high-voltage actuators (Fig. 1). Our approach is based on a light projection system that runs on low-voltage electronics, which controls an otherwise passive array of photoconductive switches connected to a high-voltage supply.  In this way, the low- and high-voltage circuits are entirely decoupled and communicate only through light patterns, which selectively turns ON or OFF photoconductive switches and thus controls the actuator array.

Fig. 1 Concept of photoactuation of high-voltage actuator arrays by light projection.

We provide details on the fabrication and characterization of photoconductive switches based on hydrogenated amorphous silicon (a-Si:H), and we propose different architectures of the switches to accommodate for different applications. To demonstrate the versatility of our approach, we showcase two applications: controlling AC-driven gate electrodes for microscale flow patterning and DC-driven electrostatic actuators for creating mechanical deformation. Video 1 shows the deformations created by an array of electrostatic actuators in response to changes in the illumination pattern. The same array could be adapted to provide smooth reconfigurable topography by stretching an elastic membrane on top of the array, as shown in Video 2. To visualize the deformation, we place a ball on the membrane and demonstrate the ability to control its trajectory by light-actuating the array.

Video 1. Deformation patterns of an array of electrostatic actuators controlled by light patterns.

Video 2. Demonstration of a reconfigurable topography enabled by light-controlled actuators.

While in this work we focus on two applications, such switching capabilities may also be useful for other high-voltage devices, such as RF devices and piezo-based devices. We also believe that our proposed approach may open the door to fast prototyping of high-voltage actuator arrays.

References

[1] Xu, C. et al. Piezoelectrically Actuated Fast Mechanical Switch for MVDC Protection. IEEE Trans. Power Deliv. 36, 2955–2964 (2021).

[2] Alves, L. F. S., Lefranc, P., Jeannin, P.-O. & Sarrazin, B. Review on SiC-MOSFET devices and associated gate drivers. in 2018 IEEE International Conference on Industrial Technology (ICIT) 824–829 (2018). doi:10.1109/ICIT.2018.8352284

[3] Mauch, D., Sullivan, W., Bullick, A., Neuber, A. & Dickens, J. High Power Lateral Silicon Carbide Photoconductive Semiconductor Switches and Investigation of Degradation Mechanisms. IEEE Trans. Plasma Sci. 43, 2021–2031 (2015).