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Actuators 2018, 7(3), 57;

Scalloping and Stress Concentration in DRIE-Manufactured Comb-Drives

Sapienza University of Rome, Dept. Structural and Geotechnical Engineering, 00184 Rome, Italy
Università degli studi Niccolò Cusano, 00166 Rome, Italy
MNF-CMM Kessler Foundation for Research, 38123 Trento, Italy
Gruppo Nazionale di Fisica Matematica, 00185 Rome, Italy
Department of Engineering, Università degli studi di Roma Tre, 00154 Rome, Italy
Current address: Dipartimento di Ingengeria, via della vasca navale 79, 00146 Rome, Italy.
Author to whom correspondence should be addressed.
Received: 23 July 2018 / Revised: 30 August 2018 / Accepted: 4 September 2018 / Published: 5 September 2018
(This article belongs to the Special Issue Micromanipulation)
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In the last decades, microelectromechanical systems have been increasing their number of degrees of freedom and their structural complexity. Hence, most recently designed MEMSs have required higher mobility than in the past and higher structural strength and stability. In some applications, device thickness increased up to the order of tens (or hundred) of microns, which nowadays can be easily obtained by means of DRIE Bosch process. Unfortunately, scalloping introduces stress concentration regions in some parts of the structure. Stress concentration is a dangerous source of strength loss for the whole structure and for comb-drives actuators which may suffer from side pull-in. This paper presents an analytical approach to characterize stress concentrations in DRIE micro-machined MEMS. The method is based on the linear elasticity equations, the de Saint-Venant Principle, and the boundary value problem for the case of a torsional state of the beam. The results obtained by means of this theoretical method are then compared with those obtained by using two other methods: one based on finite difference discretization of the equations, and one based on finite element analysis (FEA). Finally, the new theoretical approach yields results which are in accordance with the known value of the stress concentration factor for asymptotically null radius notches. View Full-Text
Keywords: scalloping; stress concentration; compliant mechanisms; DRIE scalloping; stress concentration; compliant mechanisms; DRIE

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Bertini, S.; Verotti, M.; Bagolini, A.; Bellutti, P.; Ruta, G.; Belfiore, N.P. Scalloping and Stress Concentration in DRIE-Manufactured Comb-Drives. Actuators 2018, 7, 57.

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