Clustering Transition in Thermo-Responsive Micropillars

Junsoo Kim, Ji Seong Choi, Suim Lim, Seung Eon Moon, Jong Pil Im, Jeong Hun Kim*, Seong Min Kang*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Clustering of high-aspect-ratio micropillars is a common phenomenon in nature, and has been utilized to build complex and large-scale microarchitectures. To induce the clustering, the micropillars should be prepared to be metastable, so that they cluster under perturbation, such as the drying of water. Consequently, once micropillars cluster, they cannot de-cluster spontaneously. This article shows that the micropillars of thermo-responsive hydrogels can cluster and de-cluster spontaneously and reversibly by changing the temperature. This behavior is called clustering transition. When the temperature is low, the micropillars swell and become soft. When the temperature is high, the micropillars de-swell and become stiff. This phase transition alters the lowest energy state of the system, resulting in a reversible clustering transition. To demonstrate, high-aspect-ratio micropillars of poly(N-isopropylacrylamide-co-acrylamide) hydrogels are fabricated through a soft-molding technique. The micropillars show the clustering transition, and the behavior is studied using a thermodynamic model. By controlling the temperature, the micropillars grip and release microparticles on-demand.

Original languageEnglish (US)
Article number2200023
JournalSmall Structures
Volume3
Issue number6
DOIs
StatePublished - Jun 2022

Funding

J.K. and J.S.C. contributed equally to this work. J.K. acknowledges financial support from the Kwanjeong Educational Foundation. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education(2020R1I1A3054824). This research was supported by the Basic Research Program through the National Research Foundation of Korea(NRF) funded by the MSIT(2021R1A4A1032762). This research was supported by the Basic Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education (2021R1A6A3A13044044). This work was also supported under the framework of an international cooperation program managed by the National Research Foundation of Korea (2019K2A9A1A06091737). This work was also supported by the Technology Development Program to Solve Climate Changes of the Korean NRF (2021M1A2A2061335).

Keywords

  • clustering
  • hydrogel
  • microgripper
  • thermo-responsive
  • transition

ASJC Scopus subject areas

  • General Materials Science
  • Engineering (miscellaneous)
  • Chemistry (miscellaneous)
  • Energy (miscellaneous)
  • Environmental Science (miscellaneous)

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