Multilayered microstructures with shape memory effects for vertical deployment

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TECHNICAL PAPER

Multilayered microstructures with shape memory effects for vertical deployment Zhongjing Ren1,2 • Jianping Yuan2 • Xiaoyu Su3 • Yang Xu1 • Robert Bauer1 • Sundeep Mangla4 Ming Lu5 • Yong Shi1



Received: 22 October 2020 / Accepted: 2 November 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020

Abstract This paper presents a fabrication and characterization of multilayered microstructures with shape memory effects enabling large vertical deployment under electro-thermal actuation. Our previous research demonstrated vertical deployment of such microstructures by the effect of thermal mismatch. Development of equiatomic NiTi layers in the multilayered microstructure is investigated further for shape memory effects. Multilayered microstructures are built by sputtered NiTi layers and a lift-off process. Negative photoresist ma-N1420 enables clean lift-off of 500 nm thick NiTi layers by forming a significant undercut profile after development. The parametric study on co-sputter powers for Ti and Ni50Ti50 targets suggests that 100 W RF on Ti target and 200 W DC on Ni50Ti50 target can deposit Ni49.62Ti50.38 layers. X-Ray Diffraction (XRD) and Atomic Force Microscopy (AFM) were used to study the crystal structures and surface topography of NiTi layers. XRD results of post-annealed Ni49.62Ti50.38 layers show coexistence of austenite and martensitic phases at room temperature, suggesting that the transformation temperature of such NiTi layers should be approximate 20 °C. The surface topography of Ni49.62Ti50.38 layers reveals substantial increase of surface roughness at ambient conditions after the annealing. Experimental verification of the multilayered microstructure for vertical deployment was carried out by Signatone Probe Station and Dual Scanning Electron Microscope/Focused Ion Beam (SEM/FIB) system. A vertical deployment of the two-dimensional (2D) multilayered microstructures for three-dimensional (3D) can be detected by applying a constant voltage of 0.04 V, and the expected 3D deployment displacement is enlarged from 2 lm to 10 lm by introducing the shape memory effect.

1 Introduction

Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00542-020-05101-3) contains supplementary material, which is available to authorized users.

Microstructures enabling vertical displacement have been investigated widely due to their diverse applications in developing active actuators for biomedical devices (Ghazali et al. 2020; Qiu et al. 2010; Su et al. 2019; Yan

& Zhongjing Ren [email protected]

3

School of Automation, Northwestern Polytechnical University, Xi’an 710072, China

& Jianping Yuan [email protected]

4

Downstate Medical Center, State University of New York, Brooklyn, NY 11203, USA

& Yong Shi [email protected]

5

Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, NY 11973, USA

1

Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030

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