Ultrafast small-scale soft electromagnetic robots.

High-speed locomotion is an essential survival strategy for animals, allowing populating harsh and unpredictable environments. Bio-inspired soft robots equally benefit from versatile and ultrafast motion but require appropriate driving mechanisms and device designs. Here, we present a class of small-scale soft electromagnetic robots made of curved elastomeric bilayers, driven by Lorentz forces acting on embedded printed liquid metal channels carrying alternating currents with driving voltages of several volts in a static magnetic field.

iSens: A Fiber-Based, Highly Permeable and Imperceptible Sensor Design.

Embedded sensors are key to optimizing processes and products; they collect data that allow time, energy, and materials to be saved, thereby reducing costs. After production, they remain in place and are used to monitor the long-term structural health of buildings or aircraft. Fueled by climate change, sustainable construction materials such as wood and fiber composites are gaining importance.

Soft Tunable Lenses Based on Zipping Electroactive Polymer Actuators.

Compact and entirely soft optics with tunable and adaptive properties drive the development of life-like soft robotic systems. Yet, existing approaches are either slow, require rigid components, or use high operating voltages of several kilovolts. Here, soft focus-tunable lenses are introduced, which operate at practical voltages, cover a high range of adjustable focal lengths, and feature response times in the milliseconds range.

Body Temperature-Triggered Mechanical Instabilities for High-Speed Soft Robots.

Nature offers bionic inspirations for elegant applications of mechanical principles such as the concept of snap buckling, which occurs in several plants. Exploiting mechanical instabilities is the key to fast movement here. We use the snap-through and snap-back instability observed in natural rubber balloons to design an ultrafast purely mechanical elastomer actuator.

A Lesson from Plants: High-Speed Soft Robotic Actuators.

Rapid energy-efficient movements are one of nature's greatest developments. Mechanisms like snap-buckling allow plants like the Venus flytrap to close the terminal lobes of their leaves at barely perceptible speed. Here, a soft balloon actuator is presented, which is inspired by such mechanical instabilities and creates safe, giant, and fast deformations.

Physiological relevance of epithelial geometry: New insights into the standing gradient model and the role of LI cadherin.

We introduce a mathematical model of an absorbing leaky epithelium to reconsider the problem formulated by Diamond and Bossert in 1967: whether "… some distinctive physiological properties of epithelia might arise as geometrical consequences of epithelial ultrastructure". A standing gradient model of the intercellular cleft (IC) is presented that includes tight junctions (TJ) and ion channels uniformly distributed along the whole cleft. This nonlinear system has an intrinsic homogeneous concentration and the spatial scale necessary to establish it along the cleft.

Power Balance and Temperature in Optically Pumped Spasers and Nanolasers.

Spasers and nanolasers produce a significant amount of heat, which impedes their realizability. We numerically investigate the farfield emission and thermal load in optically pumped spasers with a coupled electromagnetic/thermal model, including additional temperature discontinuities due to interfacial Kapitza resistance. This approach allows to explore multiple combinations of constitutive materials suitable for robust manufacturable spasers.

Anticorrelation of Photoluminescence from Gold Nanoparticle Dimers with Hot-Spot Intensity.

Bulk gold shows photoluminescence (PL) with a negligible quantum yield of ∼10, which can be increased by orders of magnitude in the case of gold nanoparticles. This bears huge potential to use noble metal nanoparticles as fluorescent and unbleachable stains in bioimaging or for optical data storage. Commonly, the enhancement of the PL yield is attributed to nanoparticle plasmons, specifically to the enhancements of scattering or absorption cross sections.

Minimal spaser threshold within electrodynamic framework: Shape, size and modes.

It is known (yet often ignored) from quantum mechanical or energetic considerations, that the threshold gain of the quasi-static spaser depends only on the dielectric functions of the metal and the gain material. Here, we derive this result from the purely classical electromagnetic scattering framework. This is of great importance, because electrodynamic modelling is far simpler than quantum mechanical one.

Dye-doped spheres with plasmonic semi-shells: Lasing modes and scattering at realistic gain levels.

We numerically simulate the compensation of absorption, the near-field enhancement as well as the differential far-field scattering cross section for dye-doped polystyrene spheres (radius 195 nm), which are half-covered by a silver layer of 10-40 nm thickness. Such silver capped spheres are interesting candidates for nanoplasmonic lasers, so-called spasers. We find that spasing requires gain levels less than 3.

Spectral and directional reshaping of fluorescence in large area self-assembled plasmonic-photonic crystals.

Spectral and directional reshaping of fluorescence from dye molecules embedded in self-assembled hybrid plasmonic-photonic crystals has been examined. The hybrid crystals comprise two-dimensional hexagonal arrays of dye-doped dielectric nanospheres, capped with silver semishells. Comparing the reshaped fluorescence spectra with measured transmission/reflection spectra and numerical calculations reveals that the spectral and directional reshaping of fluorescence is the result of its coupling to photonic crystal Bloch modes and to void plasmons localized inside the silver caps.

Rontgen's electrode-free elastomer actuators without electromechanical pull-in instability.

Electrical actuators made from films of dielectric elastomers coated on both sides with stretchable electrodes may potentially be applied in microrobotics, tactile and haptic interfaces, as well as in adaptive optical elements. Such actuators with compliant electrodes are sensitive to the pull-in electromechanical instability, limiting operational voltages and attainable deformations. Electrode-free actuators driven by sprayed-on electrical charges were first studied by Röntgen in 1880.

Laser-induced structure formation on stretched polymer foils.

Noncoherent structures that develop during UV laser ablation of stretched semicrystalline polymer foils are a very general phenomenon. A thermodynamic model based on stress relaxation within the modified layer of the polymer surface describes the main features of the observed phenomena, and, in particular, the dependence of the period of structures on laser wavelength, fluence, and number of laser pulses.