Dynamic multifunctional devices enabled by ultrathin metal nanocoatings with optical/photothermal and morphological versatility

Abstract

Inspired by the intriguing adaptivity of natural life, such as squids and flowers, we propose a series of dynamic and responsive multifunctional devices based on multiscale structural design, which contain metal nanocoating layers overlaid with other micro-/nanoscale soft or rigid layers. Since the optical/photothermal properties of a metal nanocoating are thickness dependent, metal nanocoatings with different thicknesses were chosen to integrate with other structural design elements to achieve dynamic multistimuli responses. The resultant devices demonstrate 1) strain-regulated cracked and/or wrinkled topography with tunable light-scattering properties, 2) moisture/photothermal-responsive structural color coupled with wrinkled surface, and 3) mechanically controllable light-shielding properties attributed to the strain-dependent crack width of the nanocoating. These devices can adapt external stimuli, such as mechanical strain, moisture, light, and/or heat, into corresponding changes of optical signals, such as transparency, reflectance, and/or coloration. Therefore, these devices can be applied as multistimuli-responsive encryption devices, smart windows, moisture/photothermal-responsive dynamic optics, and smartphone app–assisted pressure-mapping sensors. All the devices exhibit high reversibility and rapid responsiveness. Thus, this hybrid system containing ultrathin metal nanocoatings holds a unique design flexibility and adaptivity and is promising for developing next-generation multifunctional devices with widespread application.

Smart Soft Materials with Multiscale Architecture and Dynamic Surface Topographies

“…46 In addition, the finite element modeling can be performed to analyze and predict the strain related behaviors in new smart materials. 4 ■ ASSOCIATED CONTENT…”

“…In another work, as shown in Figure 5d, an Au/Pd metal nanocoating with remarkable light shielding capability laminated with a highly stretchable Ecoflex/dye substrate and other soft transparent layers was applied as a mechanochromic pressure mapping device characterized by strain tunable crack width. 4 A smartphone APP was also created to convert the colorimetric pressure sensing into a black and white false color diagram, which can be used to read pressures up to 375 kPa. This surface engineering strategy was further extended into the area of thermal modulation, as shown in Figure 5e.…”

“…Moreover, an MSR device containing a layer of 15.8 nm Au/ Pd nanocoating with decent photothermal effect and high reflectance, sandwiched by a PVA top layer and a PDMS substrate (Figure 6c) was designed and fabricated. 4 Herein, an interference-induced yellow structural color can be visualized. Also, a wrinkling surface can be generated as the device is heated followed by cooling down, ascribed to the mismatched thermal expansion coefficients of the film and the substrate.…”

“…[2][3][4]10,12 Various types of stimuli-responsive devices have been fabricated on the basis of this design strategy. 2,10,11 Another fascinating example is the wrinkling surface, which is vividly demonstrated in the petals of some flowers, 4,6 wings of insets, 6 wet human fingers, 9 and so on, 5 exhibiting distinctive light scattering/diffusing characteristics and unique adaptive responses to external stimuli. Accordingly, researchers have fabricated similar wrinkling surfaces, which were achieved via applying compression to a bilayered structure containing a thin rigid film tightly bonded to a compliant soft substrate.…”

“…6 Those artificial wrinkling surfaces can contribute to modulating the travel path of light because of refraction and/or reflection in various optical devices. [4][5][6]9,24 Therefore, the aforementioned artificial materials are expected to demonstrate dynamic, convertible, and interactive responses to various stimuli.…”