Supramolecular-structured hydrogels were prepared on basis of the inclusion complexation between poly(ethylene glycol) grafted dextrans and R-cyclodextrins (R-CDs) in aqueous media. The inclusion complexes from the PEG grafted dextrans showed a unique gel-sol phase transition which cannot be obtained from usual polymer inclusion complexes that form crystalline precipitates. The gelsol transition was based on the supramolecular assembly and dissociation, and the transition was reversible with hysteresis. The transition temperature was controllable by variation in the polymer concentration and the PEG content in the graft copolymers as well as the stoichiometric ratio between the guest and host molecules. The properties of the hydrogel were characterized by DSC, X-ray diffraction, and 13 C CP/MAS NMR. The X-ray diffraction data indicated that the gel contains a channel-type crystalline structure, demonstrated by a strong reflection at 2θ ) 20°(d ) 4.44 Å). It was confirmed from the DSC and 13 C CP/MAS NMR measurements that all the PEG grafts participate in the complexation. A phaseseparated structure consisting of hydrophobic and channel-type crystalline PEG inclusion complex domains and hydrated dextran matrices was suggested as the internal structure, which comprises the supramolecular-structured hydrogel.

Plasmonic nanostructures with enhanced localized optical fields as well as narrow linewidths have driven advances in numerous applications. However, the active engineering of ultranarrow resonances across the visible regime-and within a single system-has not yet been demonstrated. This paper describes how aluminum nanoparticle arrays embedded in an elastomeric slab may exhibit high-quality resonances with linewidths as narrow as 3 nm at wavelengths not accessible by conventional plasmonic materials. We exploited stretching to improve and tune simultaneously the optical response of as-fabricated nanoparticle arrays by shifting the diffraction mode relative to single-particle dipolar or quadrupolar resonances. This dynamic modulation of particle-particle spacing enabled either dipolar or quadrupolar lattice modes to be selectively accessed and individually optimized. Programmable plasmon modes offer a robust way to achieve real-time tunable materials for plasmon-enhanced molecular sensing and plasmonic nanolasers and opens new possibilities for integrating with flexible electronics.plasmonics | nanoparticles | lattice plasmons | mode engineering | flexible substrates S ingle plasmonic nanoparticles exhibit wide resonant linewidths that can be narrowed by diffractive coupling with neighboring particles (1-3) or nanoscale coupling to metal films (4). The integration of plasmonic nanoparticles on top of elastomeric substrates has enabled tuning of the plasmon modes (5-10), but the resonances remain broad because of radiative damping. Although long-range coupling in periodic arrays can result in extremely narrow resonances (full width at half maximum (FWHM) linewidths <5 nm) (11-13), the design criteria for these lattice plasmon modes are stringent, and the quality of the arrays is fixed at the time of fabrication. Here we report a platform that can selectively access and engineer the quality of distinct, broadband plasmon modes over the entire visible spectrum. Aluminum nanoparticle arrays embedded in an elastomeric slab exhibited high-quality resonances (FWHM: 3-7 nm) at wavelengths not possible for gold or silver and that could be continuously tailored over a large wavelength range (>100 nm). We exploited mechanical stretching to improve and tune simultaneously the optical response of asfabricated arrays by shifting the diffraction mode relative to the single-particle dipolar or quadrupolar resonances. Moreover, dipolar and quadrupolar lattice modes could be individually optimized by stretching along different array directions. The ability to realize programmable plasmon modes from a single system enables tunable substrates for fluorescence enhancement, photocatalysis, biosensing, nanolasers, as well as printed color pixels (14-21).Results Fig. 1 summarizes a platform that can achieve continuously tunable, high-quality lattice plasmon modes based on hexagonal arrays of aluminum nanoparticles embedded in an elastomeric slab. Aluminum nanostructures can support plasmon resonances spanning from the UV to near-IR becau...

This paper reports a robust and stretchable nanolaser platform that can preserve its high mode quality by exploiting hybrid quadrupole plasmons as an optical feedback mechanism. Increasing the size of metal nanoparticles in an array can introduce ultrasharp lattice plasmon resonances with out-of-plane charge oscillations that are tolerant to lateral strain. By patterning these nanoparticles onto an elastomeric slab surrounded by liquid gain, we realized reversible, tunable nanolasing with high strain sensitivity and no hysteresis. Our semiquantum modeling demonstrates that lasing build-up occurs at the hybrid quadrupole electromagnetic hot spots, which provides a route toward mechanical modulation of light-matter interactions on the nanoscale.

We report the design of three-dimensional (3D) hierarchical wrinkle substrates that can maintain their superhydrophobicity even after being repeatedly stretched. Monolithic poly­(dimethysiloxane) with multiscale features showed wetting properties characteristic of static superhydrophobicity with water contact angles (>160°) and very low contact angle hysteresis (<5°). To examine how superhydrophobicity was maintained as the substrate was stretched, we investigated the dynamic wetting behavior of bouncing and splashing upon droplet impact with the surface. On hierarchical wrinkles consisting of three different length scales, superhydrophobic bouncing was observed. The substrate remained superhydrophobic up to 100% stretching with no structural defects after 1000 cycles of stretching and releasing. Stretchable superhydrophobicity was possible because of the monolithic nature of the hierarchical wrinkles as well as partial preservation of nanoscale structures under stretching.

Periodic actuation of multiple soft, pneumatic actuators requires coordinated function of multiple, separate components. This work demonstrates a soft, pneumatic ring oscillator that induces temporally coordinated periodic motion in soft actuators using a single, constant-pressure source, without hard valves or electronic controls. The fundamental unit of this ring oscillator is a soft, pneumatic inverter (an inverting Schmitt trigger) that switches between its two states (“on” and “off”) using two instabilities in elastomeric structures: buckling of internal tubing and snap-through of a hemispherical membrane. An odd number of these inverters connected in a loop produces the same number of periodically oscillating outputs, resulting from a third, system-level instability; the frequency of oscillation depends on three system parameters that can be adjusted. These oscillatory output pressures enable several applications, including undulating and rolling motions in soft robots, size-based particle separation, pneumatic mechanotherapy, and metering of fluids. The soft ring oscillator eliminates the need for hard valves and electronic controls in these applications.

This paper describes how delamination-free, hierarchical patterning of graphene can be achieved on prestrained thermoplastic sheets by surface wrinkling. Conformal contact between graphene and the substrate during strain relief was maintained by the presence of a soft skin layer, resulting in the uniform patterning of three-dimensional wrinkles over large areas (>cm). The graphene wrinkle wavelength was tuned from the microscale to the nanoscale by controlling the thickness of the skin layer with 1 nm accuracy to realize a degree of control not possible by crumpling, which relies on delamination. Hierarchical patterning of the skin layers with varying thicknesses enabled multiscale graphene wrinkles with predetermined orientations to be formed. Significantly, hierarchical graphene wrinkles exhibited tunable mechanical stiffness at the nanoscale without compromising the macroscale electrical conductivity.

This paper describes how a memory-based, sequential wrinkling process can transform flat polystyrene sheets into multiscale, three-dimensional hierarchical textures. Multiple cycles of plasma-mediated skin growth followed by directional strain relief of the substrate resulted in hierarchical architectures with characteristic generational (G) features. Independent control over wrinkle wavelength and wrinkle orientation for each G was achieved by tuning plasma treatment time and strain-relief direction for each cycle. Lotus-type superhydrophobicity was demonstrated on three-dimensional G1-G2-G3 hierarchical wrinkles as well as tunable superhydrophilicity on these same substrates after oxygen plasma. This materials system provides a general approach for nanomanufacturing based on bottom-up sequential wrinkling that will benefit a diverse range of applications and especially those that require large area (>cm(2)), multiscale, three-dimensional patterns.

Soft skin layers on elastomeric substrates are demonstrated to support mechano-responsive wrinkle patterns that do not exhibit cracking under applied strain. Soft fluoropolymer skin layers on pre-strained poly(dimethylsiloxane) slabs achieved crack-free surface wrinkling at high strain regimes not possible by using conventional stiff skin layers. A side-by-side comparison between the soft and hard skin layers after multiple cycles of stretching and releasing revealed that the soft skin layer enabled dynamic control over wrinkle topography without cracks or delamination. We systematically characterized the evolution of wrinkle wavelength, amplitude, and orientation as a function of tensile strain to resolve the crack-free structural transformation. We demonstrated that wrinkled surfaces can guide water spreading along wrinkle orientation, and hence switchable, anisotropic wetting was realized.