title: Transformative Two-Dimensional Array Configurations by Geometrical Shape-Shifting Protein Microstructures.
abstract: Two-dimensional (2D) geometrical shape-shifting is prevalent in nature, but remains challenging in man-made "smart" materials, which are typically limited to single-direction responses. Here, we fabricate geometrical shape-shifting bovine serum albumin (BSA) microstructures to achieve circle-to-polygon and polygon-to-circle geometrical transformations. In addition, transformative two-dimensional microstructure arrays are demonstrated by the ensemble of these responsive microstructures to confer structure-to-function properties. The design strategy of our geometrical shape-shifting microstructures focuses on embedding precisely positioned rigid skeletal frames within responsive BSA matrices to direct their anisotropic swelling under pH stimulus. This is achieved using layer-by-layer two photon lithography, which is a direct laser writing technique capable of rendering spatial resolution in the sub-micrometer length scale. By controlling the shape, orientation and number of the embedded skeletal frames, we have demonstrated well-defined arc-to-corner and corner-to-arc transformations, which are essential for dynamic circle-to-polygon and polygon-to-circle shape-shifting, respectively. We further fabricate our shape-shifting microstructures in periodic arrays to experimentally demonstrate the first transformative 2D patterned arrays. Such versatile array configuration transformations give rise to structure-to-physical properties, including array porosity and pore shape, which are crucial for the development of on-demand multifunctional "smart" materials, especially in the field of photonics and microfluidics.
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371.|Institute of Materials Research and Engineering , Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602.
authors.forename: Chee Leng
authors.initials: CL
authors.lastname: Lay
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371.
authors.forename: Mian Rong
authors.initials: MR
authors.lastname: Lee
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371.|Institute of Materials Research and Engineering , Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602.
authors.forename: Hiang Kwee
authors.initials: HK
authors.lastname: Lee
authors.affiliation: Institute of Materials Research and Engineering , Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore 117602.
authors.forename: In Yee
authors.initials: IY
authors.lastname: Phang
authors.affiliation: Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371.
authors.forename: Xing Yi
authors.initials: XY
authors.lastname: Ling
mesh_terms: D000818:Animals; D002417:Cattle; D003432:Cross-Linking Reagents / Q000737:chemistry*; D004867:Equipment Design; D006863:Hydrogen-Ion Concentration; D044085:Microfluidics / Q000295:instrumentation*; D055616:Microtechnology; D012710:Serum Albumin, Bovine / Q000737:chemistry*
chemical_list: D003432:Cross-Linking Reagents; D012710:Serum Albumin, Bovine
keywords: bovine serum albumin; geometrical shape-shifting; stimuli-responsive; transformative array configurations; two-photon lithography