Integrated mechanical computing for autonomous soft machines.

Mechanical computing offers a new modality to formulate computational autonomy in intelligent matter or machines without any external powering or active elements. Transition (or solitary) waves, induced by nonreciprocity in mechanical metamaterials comprising a chain of bistable elements, have proven to be a key ingredient for dissipation-free transmission and computation of mechanical information. However, advanced processing of mechanical information in existing designs is hindered by its dissipation when interacting with networked logic gates.

High-performance electrified hydrogel actuators based on wrinkled nanomembrane electrodes for untethered insect-scale soft aquabots.

Hydrogels have diverse chemical properties and can exhibit reversibly large mechanical deformations in response to external stimuli; these characteristics suggest that hydrogels are promising materials for soft robots. However, reported actuators based on hydrogels generally suffer from slow response speed and/or poor controllability due to intrinsic material limitations and electrode fabrication technologies. Here, we report a hydrogel actuator that operates at low voltages (<3 volts) with high performance (strain > 50%, energy density > 7 × 10 joules per cubic meter, and power density > 3 × 10 watts per cubic meter), surpassing existing hydrogel actuators and other types of electroactive soft actuators.

Enhanced Flexible Mold Lifetime for Roll-to-Roll Scaled-Up Manufacturing of Adhesive Complex Microstructures.

Various functional complex 3D patterned surfaces with micro- or nanostructures have been developed and their superior performances over non-patterned smooth surfaces proven. However, it is challenging to mass-produce such complex micro-/nanopatterned surfaces, which limits their commercialization drastically. Although roll-to-roll (R2R) manufacturing using flexible molds has been implemented for mass-production of such functional surfaces, the poor mold repeatability issue has not been resolved yet.

Anisotropic Alignment of Bacterial Nanocellulose Ionogels for Unconventionally High Combination of Stiffness and Damping.

Ionogels are emerging materials for advanced electrochemical devices; however, their mechanical instability to external stresses has raised concerns about their safety. This study reports aligned bacterial nanocellulose (BC) ionogel films swelled with the model ionic liquid (IL) of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF) for an unprecedented combination of high stiffness and high energy dissipation without significant loss of ionic conductivity. The aligned BC ionogel films are prepared through wet-state stretching methods, followed by drying and swelling by ILs.

Electronic effects of nano-confinement in functional organic and inorganic materials for optoelectronics.

When various optically and/or electronically active materials, such as conjugated polymers, perovskites, metals, and metal oxides, are confined at the nanoscale, they can exhibit unique nano-confined behavior that significantly differs from the behavior observed at the macroscale. Although controlled nano-confinement of functional materials can allow modulation of their electronic properties without the aid of any synthetic methodologies or additional chemical treatments, limited assembly approaches for nano-confinement and insufficient analytical tools for electronic characterization remain critical challenges in the development of novel optoelectronic materials and the investigation of their modulated properties. This review describes how the nano-confined features of organic and inorganic materials are related to the control and improvement of their optoelectronic properties.

Electroosmosis-Driven Hydrogel Actuators Using Hydrophobic/Hydrophilic Layer-By-Layer Assembly-Induced Crack Electrodes.

Development of soft actuators with higher performance and more versatile controllability has been strongly required for further innovative advancement of various soft applications. Among various soft actuators, electrochemical actuators have attracted much attention due to their lightweight, simple device configuration, and facile low-voltage control. However, the reported performances have not been satisfactory because their working mechanism depends on the limited electrode expansion by conventional electrochemical reactions.

Enhanced Vertical Charge Transport of Homo- and Blended Semiconducting Polymers by Nanoconfinement.

The morphology of conjugated polymers has critical influences on electronic and optical properties of optoelectronic devices. Even though lots of techniques and methods are suggested to control the morphology of polymers, very few studies have been performed inducing high charge transport along out-of-plane direction. In this study, the self-assembly of homo- and blended conjugated polymers which are confined in nanostructures is utilized.

A Metal-Like Conductive Elastomer with a Hierarchical Wrinkled Structure.

For the development of wearable electronics, the replacement of rigid, metallic components with fully elastomeric materials is crucial. However, current elastomeric electrodes suffer from low electrical conductivity and poor electrical stability. Herein, a metal-like conductive elastomer with exceptional electrical performance and stability is presented, which is used to fabricate fully elastomeric electronics.

Highly Conductive Paper/Textile Electrodes Using Ligand Exchange Reaction-Induced in Situ Metallic Fusion.

Here, we report that metal nanoparticle (NP)-based paper/textile electrodes with bulk metallic conductivity can be prepared via organic linker-modulated ligand exchange reaction and in situ room-temperature metallic fusion without additional chemical or thermal treatments. For this study, amine-functionalized molecule linkers instead of bulky polymer linkers were layer-by-layer (LbL)-assembled with tetraoctylammonium bromide (TOABr)-stabilized Au NPs to form Au NP multilayered films. By conversion of the amine groups of the organic molecule linkers from -NH to the -NH groups, as well as by a decrease in the size of the organic linkers, the LbL-assembled Au NPs became highly interconnected and fused during LbL deposition, resulting in Au NP multilayers with adjustable conductivity and transport behavior.

Unraveling the Origin of Operational Instability of Quantum Dot Based Light-Emitting Diodes.

We investigate the operational instability of quantum dot (QD)-based light-emitting diodes (QLEDs). Spectroscopic analysis on the QD emissive layer within devices in chorus with the optoelectronic and electrical characteristics of devices discloses that the device efficiency of QLEDs under operation is indeed deteriorated by two main mechanisms. The first is the luminance efficiency drop of the QD emissive layer in the running devices owing to the accumulation of excess electrons in the QDs, which escalates the possibility of nonradiative Auger recombination processes in the QDs.