Reconfigurable photonic crystals enabled by pressure-responsive shape-memory polymers

Abstract

Smart shape-memory polymers can memorize and recover their permanent shape in response to an external stimulus (for example, heat). They have been extensively exploited for a wide spectrum of applications ranging from biomedical devices to aerospace morphing structures. However, most of the existing shape-memory polymers are thermoresponsive and their performance is hindered by heat-demanding programming and recovery steps. Although pressure is an easily adjustable process variable such as temperature, pressure-responsive shape-memory polymers are largely unexplored. Here we report a series of shape-memory polymers that enable unusual ‘cold' programming and instantaneous shape recovery triggered by applying a contact pressure at ambient conditions. Moreover, the interdisciplinary integration of scientific principles drawn from two disparate fields—the fast-growing photonic crystal and shape-memory polymer technologies—enables fabrication of reconfigurable photonic crystals and simultaneously provides a simple and sensitive optical technique for investigating the intriguing shape-memory effects at nanoscale.

Direct Writing of Three-Dimensional Macroporous Photonic Crystals on Pressure-Responsive Shape Memory Polymers

“…We have recently discovered a new type of stimuli-responsive shape memory polymer that enables unusual "cold" programming (i.e., the deformation from the permanent shape to the temporary configuration occurs at room temperature) and instantaneous shape recovery at ambient conditions triggered by applying a static contact pressure or exposing the polymer to various organic vapors (e.g., acetone and toluene). [30][31] These new SMPs are composed of photocured copolymers of ethoxylated (20) trimethylolpropane triacrylate (ETPTA 20) and polyethylene glycol (600) diacrylate (PEGDA 600) oligomers with varying volumetric ratios from 1:1 to 1:6. Figure 1 shows an exemplary pressure-induced SM recovery process using an ETPTA 20-co-PEGDA 600 copolymer with a 1:3 volumetric ratio.…”

“…To explain this counterintuitive pressure-induced recovery of collapsed macropores, we proposed a SM recovery mechanism triggered by an adhesive pull-off force caused by the attractive van der Waals interactions between the rubber stamp and the pressure-responsive SMP membrane. 30 However, this new recovery mechanism is far from being thoroughly investigated and verified. Here we explore a new direct writing technology for inscribing arbitrary 3D photonic crystal patterns on the above pressure-responsive SMP membranes.…”

“…28 Another major merit of the current technology is the employment of new pressure-sensitive SMPs that enable the direct writing of arbitrary 3D macroporous photonic crystal patterns on the polymer surface in a single step. [30][31] Shape memory polymers are a class of smart materials that can recover their "memorized" permanent shapes triggered by various external stimuli, such as heat, light, solvent, and electromagnetic field. [22][23][32][33][34][35][36][37][38][39][40][41] Shape memory (SM) effects in traditional SMPs are usually achieved in three steps − programming, storage, and recovery.…”

pH and redox-operated nanovalve for size-selective cargo delivery on hollow mesoporous silica spheres

“…Compared with normal cells, tumors have a more acidic internal environment, which shows an excellent prospect for developing pH-responsive mechanized MSNs [29]. To design the stimulus responsive materials, responsive groups were usually introduced into materials [30][31][32][33][34]. Several acidic-sensitive linkers have been reported to form pH stimuliresponsive system, such as a reversible boronate ester linker [35], hydrazones bond [36], imines bond [37] and acetal linker [38].…”

Optimal Design of Photonic Band-Gap Structure Based on Kriging Surrogate Model

“…Photonic crystals are also named photonic band-gap (PBG) structures because of their ability of allowing or forbidding the propagation of light within certain frequency ranges [1,2]. The photonic band-gaps in a photonic crystal structure play a vital role to realize various applications [3][4][5] in the field of optical technology. Specific band-gap is required in practice, so it is of great significance to design photonic band-gaps within certain frequency ranges.…”