| AVS 64th International Symposium & Exhibition | |
| MEMS and NEMS Group | Tuesday Sessions |
| Session MN-TuP |
| Session: | MEMS/NEMS Poster Session |
| Presenter: | Ratul Majumdar, University of Illinois at Chicago |
| Authors: | R. Majumdar, University of Illinois at Chicago L. Stan, Argonne National Laboratory R. Divan, Argonne National Laboratory I. Paprotny, University of Illinois at Chicago |
| Correspondent: | Click to Email |
Untethered Scratch Drive Actuators (USDAs) [1] have been widely used for actuation of MEMS devices, for example the assembly of 3D MEMS structures [2] and as propulsion mechanisms for stress-engineered MEMS microrobots [1]. These electrostatic actuators show fast and reliable motion on a power delivery substrate along with the ability to provide forward force of 30μN [2]. The power delivery substrate of these USDAs consist of parallel set of interdigitated metal electrodes with a high-k dielectric layer deposited on top [1,3]. The metal electrodes consist of Cr/Au/Cr(10/50/10nm) layers of 2 μm spacing patterned by electron beam lithography. Sputtered yittria-stabilized zirconium oxide (YSZ) of 500μm thickness is used as the dielectric layer. The sputtering parameters, especially the deposition pressure, along with the gas flow of argon and oxygen play an important role in determining the dielectric constant and hence, the power transferred to the USDA for actuation. Variation in the deposition pressure can improve adhesion of the dielectric layer and reduce the delamination during USDA motion. Application of ac voltage between the two parallel set of electrodes results in coupling of capacitive force to the microrobot chassis, thus supplying power to backplate and bushing of the USDA for translation.
For straight motion, a waveform primitive (Fig. 1, supplemental file) with amplitude ranging from 0 to 200V and frequency (f) of 15Hz was applied to the substrate. The waveform is symmetric along horizontal X axis to prevent accumulation of charge on the substrate. The lowest (Vlow) and highest (Vhigh) value of the voltage waveform is varied and the corresponding motion of the USDA is recorded. The cutoff point at which USDA shows actuation depends on the quality of the dielectric (Fig.2). Interesting interaction with the substrate during release stage is observed by analyzing the Vlow (Fig. 3 and 4). Improved efficiency of the substrate by transferring more power to the USDA is observed for the power delivery substrate with the YSZ grown at higher pressure (25mTorr). That results in reliable motion and less delamination of the dielectric surface.
References
[1] Donald et. al.,ISRR. Springer,2005,pp.502–516.
[2] Akiyama et. al.,JMEMS,vol. 6,no. 1,pp.10–17,1997.
[3] Majumdar et. al.,JMEMS,doi.org/10.1109/JMEMS.2017.2689679 .