Stretching soft matter performance: From conformable electronics and soft machines to renewable energy
The Soft-Map project intended to introduce paradigm shifts in three major areas, in electronics, machines and energy harvesting, from traditional devices based on hard materials to soft ones. In electronics, the project contributed to ultra-flexible and stretchable electronics in various ways. Introducing ultra-lightweight forms of “imperceptible” electronics enabled the fabrication of solar cells with a power per weight of 20 W/g, mechanically stretchable displays and tactile sensor arrays, as well as plastic electronic sensor wrap. Potential applications arise in smart appliances for leisure, sport and healthcare, intimately integrating electronics in our daily life without impairing quality of life. In terms of intrinsically stretchable electronic devices, the project contributed concepts for mechanically stretchable and rechargeable batteries, potentially useful in wearables. By introducing tough bonding between hydrogels and various materials, from hard metals and ceramics, to polymers and soft elastomers, potentially leading to large area hydrogel electronic skins for thermally triggered drug release in mobile health. In the field of soft machines, we analysed the potential of dielectric elastomer technology. We showed how to model viscous losses and leakage in the description of actuators and energy generators, and we explored the use of electrically triggered mechanical instabilities for large stroke actuation. Dielectric elastomer membranes also seem promising for harvesting energy from mechanical sources, ranging from human gait to ocean waves. In particular we have shown that the levelized cost of electricity generation from soft energy harvesters may favourable compare with existing technologies, for example solar energy. In addition, the carbon dioxide footprint of soft energy generators appears highly promising. Based on the introduction of allowable states in work conjugate plots, we were able to predict useful materials for such energy harvesters; experimentally we confirmed that natural rubber, a sustainable material, nicely fulfils most of the criteria for energy harvesters. The Soft-Map project launched eight highly cited papers, indicating significant impact of our work, revealing that we were able to induce a paradigm shift in the three core aims of the project. The technology developed within the Soft-Map project was also transferred to industry, with first products in new human machine interactions already close to commercialization. Here the large area optical position detection sensors of the project form the heart of the q-technology of isiQiri, namely the q-pen, q-frame and q-glass. Follow-up projects on the national and European level guarantee further development of the Soft-Map concepts in 3d moldable electronic appliances and in ocean wave energy harvesting with dielectric elastomer membranes.