Moisture-harvesting lizards such as the Texas horned lizard (Iguanidae: Phrynosoma cornutum) live in arid regions. Special skin adaptations enable them to access water sources such as moist sand and dew: their skin is capable of collecting and transporting water directionally by means of a capillary system between the scales. This fluid transport is passive, i.e. requires no external energy, and directs water preferentially towards the lizard's snout. We show that this phenomenon is based on geometric principles, namely on a periodic pattern of interconnected half-open capillary channels that narrow and widen. Following a biomimetic approach, we used these principles to develop a technical prototype design. Building upon the Young-Laplace equation, we derived a theoretical model for the local behaviour of the liquid in such capillaries. We present a global model for the penetration velocity validated by experimental data. Artificial surfaces designed in accordance with this model prevent liquid flow in one direction while sustaining it in the other. Such passive directional liquid transport could lead to process improvements and reduction of resources in many technical applications.

Sustainable natural rubber for soft generators opens up new possibilities for harvesting renewable resources. With this technology, ocean wave energy could become a cheap and clean resource for generation of electricity.

Dielectric elastomers are used for electromechanical energy conversion in actuators and in harvesting mechanical energy from renewable sources. The electrical breakdown strength determines the limit of a dielectric elastomer for its use in actuators and energy harvesters. We report two experimental configurations for the measurement of the stretch dependence of the electrical breakdown strength of dielectric elastomers, and compare the electrical breakdown fields for compliant and rigid electrodes on the elastomer. We show that the electrode configuration strongly influences the electrical breakdown field strength. Further, we compare the stretch dependent dielectric function and breakdown of the acrylic elastomer VHB 4910™ from 3M™, and of the natural rubber ZruElast™ A1040™ from Zrunek rubber technology. While the dielectric permittivity of VHB decreases with increasing stretch ratio, the dielectric constant of rubber is insensitive to stretch. Our results suggest natural rubber as a versatile material for dielectric elastomer energy harvesting.

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/advs.201903391. This publication is dedicated to Siegfried Bauer, who has sadly passed away during the course of this work 5th Anniversary Article [ †] Deceased December 2018.

Conventional refrigeration relies on hazardous agents, contributing to global warming. Soft, cheap, biodegradable solid-state elastocaloric cooling based on natural rubber offers an environmental friendly alternative. However, no such practical cooler has been developed, as conventional soft elastocaloric designs are not fast enough to ensure adiabaticity.In this work, we combine snap-through instability with strain-induced crystallization and achieve a sub-100 ms quasi-adiabatic cycling which is 30 times faster than previous design.Negligible heat exchange in expansion/contraction stages combined with the latent heat of phase transitions result in a giant elastocaloric crystallization effect. The rubber-based all-soft heat pump enables a specific cooling power of 20.9 W/g, a heat-flux of 256 mW/cm 2 , a coefficient of performance of 4.7 and a single-stage temperature span between hot and cold reservoirs of 7.9 K (full adiabatic temperature change of rubber membrane exceeding 23 K).The pump permits a compact all-soft voltage-actuated setup, opening up the opportunity of a viable plug-in-ready cooling device.