title: Control of Reversible Self-Bending Behavior in Responsive Janus Microstrips.
abstract: Here, we demonstrate a simple method to systematically control the responsive self-bending behavior of Janus hydrogel microstrips consisting of a polymeric bilayer with a high modulus contrast. The Janus hydrogel microstrips could be easily fabricated by a simple micromolding technique combined with an initiated chemical vapor deposition (iCVD) coating, providing high flexibility in controlling the physical and chemical properties of the microstrips. The fabricated Janus hydrogel microstrip is composed of a soft, pH-responsive polymer hydrogel layer laminated with a highly cross-linked, rigid thin film, generating a geometric anisotropy at a micron scale. The large difference in the elastic moduli between the two layers of the Janus microstrips leads to a self-bending behavior in response to the pH change. More specifically, the impact of the physical and chemical properties of the microstrip on the self-bending phenomena was systematically investigated by changing the thickness and composition of two layers of the microstrip, which renders high controllability in bending of the microstrips. The curvature of the Janus microstrips, formed by self-bending, highly depends on the applied acidity. A reversible, responsive self-bending/unbending exhibits a perfect resilience pattern with repeated changes in pH for 5 cycles. We envision that the Janus microstrips can be engineered to form complex 3D microstructures applicable to various fields such as soft robotics, scaffolds, and drug delivery. The reliable responsive behaviors obtained from the systematic investigation will provide critical information in bridging the gap between the theoretical mechanical analysis and the chemical properties to achieve micron-scale soft robotics.
authors.affiliation: Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST) , Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Myung Seok
authors.initials: MS
authors.lastname: Oh
authors.affiliation: Department of Chemical Engineering, Chungnam National University , Yuseong-gu, Daejeon 305-764, Republic of Korea.
authors.forename: Young Shin
authors.initials: YS
authors.lastname: Song
authors.affiliation: Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST) , Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Cheolgyu
authors.initials: C
authors.lastname: Kim
authors.affiliation: Department of Chemical Engineering, Chungnam National University , Yuseong-gu, Daejeon 305-764, Republic of Korea.
authors.forename: Jongmin
authors.initials: J
authors.lastname: Kim
authors.affiliation: Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST) , Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Jae Bem
authors.initials: JB
authors.lastname: You
authors.affiliation: Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST) , Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Taek-Soo
authors.initials: TS
authors.lastname: Kim
authors.affiliation: Department of Chemical Engineering, Chungnam National University , Yuseong-gu, Daejeon 305-764, Republic of Korea.
authors.forename: Chang-Soo
authors.initials: CS
authors.lastname: Lee
authors.affiliation: Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST) , Yuseong-gu, Daejeon 305-701, Republic of Korea.
authors.forename: Sung Gap
authors.initials: SG
authors.lastname: Im
keywords: Janus microstrip; initiated chemical vapor deposition (iCVD); micromolding; pH responsivity; self-bending