Abstract
In the last years, stimuli-responsive polymeric materials have attracted great interest, due to their low cost and ease of structuration over large areas combined with the possibility to actively manipulate their properties. In this work, we propose a polymeric pattern of soft-imprinted microwells containing azobenzene molecules. The shape of individual elements of the pattern can be controlled after fabrication by irradiation with properly polarized light. By taking advantage of the light responsivity of the azobenzene compound, we demonstrate the possibility to reversibly modulate a contraction-expansion of wells from an initial round shape to very narrow slits. We also show that the initial shape of the microconcavities can be restored by flipping the polarization by 90°. The possibility to reversibly control the final shape of individual elements of structured surfaces offers the opportunity to engineer surface properties dynamically, thus opening new perspectives for several applications.
Highlights
In recent years, the ability to pattern large areas of stimuliresponsive materials at the micro- and nanoscale has opened the opportunity to engineer surface structures and trigger peculiar properties such as complex optical functionalities [1] or surface properties [2] by light-matter interactions
By taking advantage of the light responsivity of the azobenzene compound, we demonstrate the possibility to reversibly modulate a contraction-expansion of wells from an initial round shape to very narrow slits
Over the last two decades, the progress on micro- and nanoscale research has enabled the development of several patterning techniques, including soft lithography [3], nanoimprint lithography [4], interference lithography, and advanced photo lithography [5]
Summary
The ability to pattern large areas of stimuliresponsive materials at the micro- and nanoscale has opened the opportunity to engineer surface structures and trigger peculiar properties such as complex optical functionalities [1] or surface properties [2] by light-matter interactions. Micro- and nanofabrication technology finds applications in a plethora of fields, such as optics and photonics [6], microfluidics [7], and even biology [8]. Despite such impressive achievements, most of the conventional patterning techniques result in static structures, whose features cannot be modified after fabrication. To overcome such limitation, Karageorgiev et al proposed exploiting the photoresponsivity of azopolymers in a technique named Directional Photofluidization Lithography [9,10,11], the term “photofluidization” is controversial as the fundamental mechanism underlying such effect is still under debate [12]. Based on the same approach, here we propose a reversible manipulation of prefabricated azopolymeric structures driven by polarized light
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