Abstract
A chromatic vectorial strain sensor constituted by hexagonal voids on transparent elastomeric substrate has been successfully fabricated via soft colloidal lithography. Initially a highly ordered 1.6 microns polystyrene spheres monolayer colloidal crystal has been realized by wedge-shaped cell method and used as a suitable mold to replicate the periodic structure on a polydimethylsiloxane sheet. The replicated 2D array is characterized by high periodicity and regularity over a large area, as evidenced by morphological and optical properties obtained by means of SEM, absorption and reflectance spectroscopy. In particular, the optical features of the nanostructured elastomer have been investigated in respect to uniaxial deformation up to 10% of its initial length, demonstrating a linear, tunable and reversible response, with a sensitivity of 4.5 ± 0.1 nm/%. Finally, it has been demonstrated that the specific geometrical configuration allows determining simultaneously the vectorial strain-stress information in the x and y directions.
Highlights
Among the different fabrication techniques that allow obtaining micro/nanostructured surfaces, colloidal lithography is attracting big interest due to low cost, time efficiency, simplicity, and the possibility to pattern over a large surface area [1].This bottom-up approach exploits the self-assembly of hard dielectric micro and nano spheres such as silica or polystyrene (PS) in order to fabricate two dimensional arrays
A chromatic vectorial strain sensor constituted by hexagonal voids on transparent elastomeric substrate has been successfully fabricated via soft colloidal lithography
A highly ordered 1.6 microns polystyrene spheres monolayer colloidal crystal has been realized by wedge-shaped cell method and used as a suitable mold to replicate the periodic structure on a polydimethylsiloxane sheet
Summary
Among the different fabrication techniques that allow obtaining micro/nanostructured surfaces, colloidal lithography is attracting big interest due to low cost, time efficiency, simplicity, and the possibility to pattern over a large surface area [1]. 2D colloidal crystals have been realized by self-assembly under electrophoresis deposition [2], Langmuir–Blodgett deposition [3], spin coating [4] and capillary forces [5] Considering this last approach, Sun et al [6] have demonstrated that the use of wedge-shaped cell allows obtaining large domains 2D colloidal crystals, with centimeter size, taking advantage on the capillary forces and drying front formed in the cell. In micro and nano patterning field, colloidal crystals can be employed as lithographic masks or as molds for the production of micro and nanostructures for light trapping applications [8] or for the realization of SERS (Surface Enhanced Raman Spectroscopy) substrates [9] They can act as masters by means of soft lithography in order to produce hexagonally arrayed structures. This structure paves the way for the development of low cost vector strain sensor systems
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