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Surface-Controlled Molecular Self-Alignment in Polymer Actuators for Flexible Microrobot Applications

Center for Bionics, Korea Institute of Science and Technology, Seoul 02792, Korea
School of Chemical Engineering, Sungkyunkwan University, Suwon 16419, Korea
School of Electrical Engineering, Korea University, Seoul 02841, Korea
SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan University, Suwon 16419, Korea
Department of Biomedical Engineering, Sungkyunkwan University, Suwon 16419, Korea
Department of Mechanical Engineering, Southern Methodist University, Dallas, TX 75275, USA
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Polymers 2019, 11(4), 736;
Received: 26 March 2019 / Revised: 14 April 2019 / Accepted: 18 April 2019 / Published: 23 April 2019
PDF [2274 KB, uploaded 23 April 2019]


Polymer actuators are important components in lab-on-a-chip and micromechanical systems because of the inherent properties that result from their large and fast mechanical responses induced by molecular-level deformations (e.g., isomerization). They typically exhibit bending movements via asymmetric contraction or expansion with respect to changes in environmental conditions. To enhance the mechanical properties of actuators, a strain gradient should be introduced by regulating the molecular alignment; however, the miniaturization of polymer actuators for microscale systems has raised concerns regarding the complexity of such molecular control. Herein, a novel method for the fabrication of micro-actuators using a simple molecular self-alignment method is presented. Amphiphilic molecules that consist of azobenzene mesogens were located between the hydrophilic and hydrophobic surfaces, which resulted in a splayed alignment. Thereafter, molecular isomerization on the surface induced a large strain gradient and bending movement of the actuator under ultraviolet-light irradiation. Moreover, the microelectromechanical systems allowed for the variation of the actuator size below the micron scale. The mechanical properties of the fabricated actuators such as the bending direction, maximum angle, and response time were evaluated with respect to their thicknesses and lengths. The derivatives of the polymer actuator microstructure may contribute to the development of novel applications in the micro-robotics field. View Full-Text
Keywords: polymer actuator; self-alignment; azobenzene; microelectromechanical systems polymer actuator; self-alignment; azobenzene; microelectromechanical systems

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Jang, M.; Kim, J.S.; Kim, J.-H.; Bae, D.H.; Kim, M.J.; Son, D.; Kim, Y.-T.; Um, S.H.; Kim, Y.H.; Kim, J. Surface-Controlled Molecular Self-Alignment in Polymer Actuators for Flexible Microrobot Applications. Polymers 2019, 11, 736.

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