Strain-controlled Graphene-Polymer Angular Actuator
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MRS Advances © 2019 Materials Research Society DOI: 10.1557/adv.2019.276
Strain-controlled Graphene-Polymer Angular Actuator S. Matt Gilbert1,2,3, Adam Molnar1,3, Donez Horton-Bailey1,2,3, Helen Y. Yao1,3, Alex Zettl1,2,3 1
Department of Physics, University of California, Berkeley, CA, 94720
2
Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720
3
Kavli Energy Nanosciences Institute, Berkeley, CA, 94720
ABSTRACT
We demonstrate a suspended graphene-(poly(methyl methacrylate) (PMMA) polymer angular displacement actuator enabled by variable elastic modulus of the perforated stacked structure. Azimuthal flexures support a central disc-shaped membrane, and compression of the membrane can be used to control the rotation of the entire structure. Irradiating the PMMA on graphene stack with 5 kV electrons in a convention scanning electron microscope reduces the elastic modulus of the PMMA and allows graphene’s built in strain to dominate and compress the flexures, thus rotating the actuator.
INTRODUCTION The patterning and etching of suspended two-dimensional materials is a powerful method to control their mechanical properties and functionalities [1]–[3]. It has been demonstrated that the cutting of graphene resonators can be used to tune their maximum displacement, quality factor, and resonance frequency [1], [2]. Moreover, these schemes have been used to introduce mechanical motion; for example, the patterning of graphene-glass bimorphs has been shown to allow for autonomous selffolding, and graphene kirgami can be used to form dynamic 3D structures [2], [3]. As the ability to pattern two-dimensional materials approaches the single atom scale [4], [5], these methods are templates for machines that can interact with their environment at both the nano- and micro- scales. However, in order to study these mechanical systems,
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specialized equipment like mechanical probes and laser interferometers are required to drive and detect their motion [2]. In this work, we report a novel angular displacement graphene-based mechanical device that uses only a conventional scanning electron microscope (SEM) or electron beam lithography system, common to many standard fabrication facilities, to both drive and detect its motion. The device consists of a patterned PMMA (poly(methyl methacrylate)) on graphene laminate, and rotational actuation is enabled by relaxation of the built in strain of the graphene. Azimuthal flexures support a central membrane, and compression of the membrane, via electron irradiation[6], produces rotation. The method demonstrates that irradiation from a conventional scanning electron microscope or electron beam lithography tool can be used to control the motion and rotation of suspended membranes, suggesting that this technique can
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