Better Actuation Through Chemistry: Using Surface Coatings to Create Uniform Director Fields in Nematic Liquid Crystal Elastomers
Abstract
Controlling the molecular alignment of liquid crystal monomers (LCMs) within nano- and microstructures is essential in manipulating the actuation behavior of nematic liquid crystal elastomers (NLCEs). In this paper, we study how to induce uniformly vertical alignment of nematic LCMs within a micropillar array to maximize the macroscopic shape change using surface chemistry. Landau–de Gennes numerical modeling suggests that it is difficult to perfectly align LCMs vertically in every pore within a poly(dimethylsiloxane) (PDMS) mold with porous channels during soft lithography. In an untreated PDMS mold that provides homeotropic anchoring of LCMs, a radially escaped configuration of LCMs is observed. Vertically aligned LCMs, a preferred configuration for actuation, are only observed when using a PDMS mold with planar anchoring. Guided by the numerical modeling, we coat the PDMS mold with a thin layer of poly(2-hydroxyethyl methacrylate) (PHEMA), leading to planar anchoring of LCM. Confirmed by polarized optical microscopy, we observe monodomains of vertically aligned LCMs within the mold, in agreement with modeling. Finally, after curing and peeling off the mold, the resulting NLCE micropillars showed a relatively large and reversible radial strain (~30%) when heated above the nematic to isotropic transition temperature.
- Authors:
-
- Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Materials Science and Engineering
- Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Materials Science and Engineering; Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Engineering Directorate
- Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Materials Science and Engineering. Dept. of Physics and Astronomy
- Harvard Univ., Cambridge, MA (United States). Paulson School of Engineering and Applied Sciences
- Johannes Gutenberg Univ. Mainz (Germany). Inst. of Organic Chemistry
- Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Physics and Astronomy
- Publication Date:
- Research Org.:
- Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States); Univ. of Pennsylvania, Philadelphia, PA (United States)
- Sponsoring Org.:
- USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF); Simons Foundation (United States)
- OSTI Identifier:
- 1465270
- Report Number(s):
- LLNL-JRNL-747546
Journal ID: ISSN 1944-8244; 932396
- Grant/Contract Number:
- AC52-07NA27344; DMR-1120901; DMR-1410253; DMR12-62047
- Resource Type:
- Accepted Manuscript
- Journal Name:
- ACS Applied Materials and Interfaces
- Additional Journal Information:
- Journal Volume: 8; Journal Issue: 19; Journal ID: ISSN 1944-8244
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; actuator; liquid crystal elastomer; monodomain; soft lithography; surface chemistry
Citation Formats
Xia, Yu, Lee, Elaine, Hu, Hao, Gharbi, Mohamed Amine, Beller, Daniel A., Fleischmann, Eva-Kristina, Kamien, Randall D., Zentel, Rudolf, and Yang, Shu. Better Actuation Through Chemistry: Using Surface Coatings to Create Uniform Director Fields in Nematic Liquid Crystal Elastomers. United States: N. p., 2016.
Web. doi:10.1021/acsami.6b02789.
Xia, Yu, Lee, Elaine, Hu, Hao, Gharbi, Mohamed Amine, Beller, Daniel A., Fleischmann, Eva-Kristina, Kamien, Randall D., Zentel, Rudolf, & Yang, Shu. Better Actuation Through Chemistry: Using Surface Coatings to Create Uniform Director Fields in Nematic Liquid Crystal Elastomers. United States. https://doi.org/10.1021/acsami.6b02789
Xia, Yu, Lee, Elaine, Hu, Hao, Gharbi, Mohamed Amine, Beller, Daniel A., Fleischmann, Eva-Kristina, Kamien, Randall D., Zentel, Rudolf, and Yang, Shu. Fri .
"Better Actuation Through Chemistry: Using Surface Coatings to Create Uniform Director Fields in Nematic Liquid Crystal Elastomers". United States. https://doi.org/10.1021/acsami.6b02789. https://www.osti.gov/servlets/purl/1465270.
@article{osti_1465270,
title = {Better Actuation Through Chemistry: Using Surface Coatings to Create Uniform Director Fields in Nematic Liquid Crystal Elastomers},
author = {Xia, Yu and Lee, Elaine and Hu, Hao and Gharbi, Mohamed Amine and Beller, Daniel A. and Fleischmann, Eva-Kristina and Kamien, Randall D. and Zentel, Rudolf and Yang, Shu},
abstractNote = {Controlling the molecular alignment of liquid crystal monomers (LCMs) within nano- and microstructures is essential in manipulating the actuation behavior of nematic liquid crystal elastomers (NLCEs). In this paper, we study how to induce uniformly vertical alignment of nematic LCMs within a micropillar array to maximize the macroscopic shape change using surface chemistry. Landau–de Gennes numerical modeling suggests that it is difficult to perfectly align LCMs vertically in every pore within a poly(dimethylsiloxane) (PDMS) mold with porous channels during soft lithography. In an untreated PDMS mold that provides homeotropic anchoring of LCMs, a radially escaped configuration of LCMs is observed. Vertically aligned LCMs, a preferred configuration for actuation, are only observed when using a PDMS mold with planar anchoring. Guided by the numerical modeling, we coat the PDMS mold with a thin layer of poly(2-hydroxyethyl methacrylate) (PHEMA), leading to planar anchoring of LCM. Confirmed by polarized optical microscopy, we observe monodomains of vertically aligned LCMs within the mold, in agreement with modeling. Finally, after curing and peeling off the mold, the resulting NLCE micropillars showed a relatively large and reversible radial strain (~30%) when heated above the nematic to isotropic transition temperature.},
doi = {10.1021/acsami.6b02789},
journal = {ACS Applied Materials and Interfaces},
number = 19,
volume = 8,
place = {United States},
year = {Fri May 06 00:00:00 EDT 2016},
month = {Fri May 06 00:00:00 EDT 2016}
}
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