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Mechanoereceptors embedded in the glabrous skin of the human hand encode a range of physical stimuli e.g. pressure, strain, and temperature. The shape, softness, and distributed modalities of the natural skin make it challenging to replicate with synthetic materials. Using stretchable metallization on soft, elastomeric carrier substrates, we have optimized and implemented a multimodal electronic skin covering the dorsal and palmar sides of the fingers. The wearable tactile skin includes resistive sensors monitoring finger articulation and capacitive pressure sensors that register distributed pressure along the entire length of the finger. The next challenge is the integration of a soft thin-film transistor "backplane" with the "frontplane" sensors to engineer a high-density, highly distributed tactile electronic skin. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents different ways of storing electricity to overcome the intermittency of renewable energies. After reviewing existing storage technologies, a new way of storing electricity thermodynamically on a large scale is presented. This system is based on the principle of a high temperature heat pump that converts electricity into heat. This thermal energy is stored in refractory materials, and at a later stage converted into electricity by means of a Joule cycle. The first mode -of energy storage- requires the use of turbomachinery - compressors and turbines - to operate under conditions different from those usually encountered. In particular, for the process to be efficient, the compressor must operate at high temperatures (500 to 1000° C). This represents a major technological barrier in the process due to the market unavailability of compressors capable of operating under such conditions. In this study the latest advances in the field of gas turbines are presented, including those concerning high pressure turbine blades, in order to adapt them to the compressor. These advances result mainly in changes in the composition of nickel-based superalloys and their implementation (single crystals) to achieve maximum wall temperatures around 950°C. [Copyright &y& Elsevier]

Abstract: Soft bioengineered surfaces offer a route towards modulating the tissue responses to chronically implanted devices and may enhance their functionality. In this communication we fabricate microtopographically rich and mechanically compliant silicone surfaces for use in soft neural interfaces. We observe the interaction of primary rat microglia and astroglia with arrays of tall and short (4.7 and 0.5μm) vertically oriented polydimethylsiloxane (PDMS) micropillars and a flat PDMS surface in vitro. With the pillar size and spacing that we use (1.3μm diameter and 1.6μm edge to edge), glia are found to engulf and bend tall pillars. The cytoskeleton of cells adhering to the pillar arrays lacks actin stress fibers; instead we observe actin ring formations around individual pillars. Tall, but not short pillar arrays are inhibitory to migration and spreading for both microglia and astrocytes. When compared to a flat PDMS surface and short pillar arrays, tall micropillar arrays cause nearly a 2-fold decrease in proliferation rates for both cell types. The antimitotic properties of tall pillar arrays may be useful for reducing the density of the glial capsule around brain-implanted devices. [Copyright &y& Elsevier]

Previously we reported a finite-element model that predicted that microchannels could be sensitive recording devices, amplifying the extracellular signal as action potentials pass through them, and making recording independent of node of Ranvier location. Here, we present an in vitro experimental study that validates these predictions and also demonstrates that microchannel electrode can be highly efficient stimulators. Several aspects of whole-nerve Fuff technology, including noise-reduction techniques and unidirectional stimulation methods, are readily transferable to this small scale. If axons can be persuaded to regenerate in large numbers through narrow channels, the results presented here suggest that a regenerative microchannel array could be used to produce an in vivo peripheral nerve interface with a high-resolution for both recording and stimulation. [ABSTRACT FROM AUTHOR]

A thin film of a stiff material, patterned as a serpentine on a fliat elastomeric substrate, can elongate substantially when the substrate is pulled. We showed that the film elongates by twisting out of plane, accommodated by the compliance of the substrate and the pattern of the film. Consequently, large elongations of the substrate induce small strains in the film, even when the width of the film is much larger than its thickness. Such a wide serpentine, or other compliant patterns of stiff materials, can serve as a platform on which electronic circuits can be fabricated. This architecture will make electronics elastically stretchable. [ABSTRACT FROM AUTHOR]

Elastic electronic surfaces will integrate stiff thin film devices onto compliant polymer substrates. These surfaces may be stretched once or many times, by up to tens of percent strain. One way to make such an elastic electronic surface is to distribute rigid subcircuit islands over the polymer surface, and then fabricate active devices on the islands. These islands need to be interconnected with stretchable metallization. We describe stretchable interconnects made of stripes of thin gold film patterned on elastomeric membranes. These membranes can be stretched by up to twice their initial length and maintain electrical conduction. We review the fabrication of these conductors, present their electrical and mechanical properties, and summarize our model for their extreme stretchability. Using such stretchable interconnects, we made the first elastic circuit, an inverter of thin film transistors. The circuit remains functional when stretched and relaxed by 12% strain. [ABSTRACT FROM AUTHOR]

This paper describes a three-dimensional chemistry transport model, POLAIR, with a special focus on numerical aspects. POLAIR is a fully modular eulerian model. Several different chemical mechanisms are available, which can deal with photochemistry (Racm, Radm, etc.), continental impact (e.g. passive transport), mercury, aerosols, etc. POLAIR is designed to enable simulations from regional scales to continental scales. A few simulations at those scales have been conducted to assess and improve the code. Beyond forward simulations, inverse modelling and data assimilation can be performed, thanks to the tangent linear and adjoint versions of POLAIR, which are available through automatic differentiation. [ABSTRACT FROM AUTHOR]

Traditional microelectrode arrays (MEAs) are limited to measuring electrophysiological activity in two dimensions, failing to capture the complexity of three-dimensional (3D) tissues such as neural organoids and spheroids. Here, we introduce a flower-shaped MEA (e-Flower) that can envelop submillimeter brain spheroids following actuation by the sole addition of the cell culture medium. Inspired by soft microgrippers, its actuation mechanism leverages the swelling properties of a polyacrylic acid hydrogel grafted to a polyimide substrate hosting the electrical interconnects. Compatible with standard electrophysiology recording systems, the e-Flower does not require additional equipment or solvents and is ready to use with preformed 3D tissues. We designed an e-Flower achieving a curvature as low as 300 micrometers within minutes, a value tunable by the choice of reswelling media and hydrogel cross-linker concentration. Furthermore, we demonstrate the ability of the e-Flower to detect spontaneous neural activity across the spheroid surface, demonstrating its potential for comprehensive neural signal recording. [ABSTRACT FROM AUTHOR]

Reliable long‐term function is crucial for flexible and soft bioelectronics. Mechanical defects and permeation of water molecules across the various device layers are the prime drivers of failure, and particularly in applications requiring continuous contact with biofluids (i.e. for implantable applications). To address demanding needs of miniaturization, mechanical compliance and water impermeability, ultra‐thin high‐barrier encapsulations are a promising way to improve device reliability. In this work, the encapsulation properties of vapour phase infiltration (VPI) of inorganic Al2O3 layers deposited by atomic layer deposition (ALD), as bilayers with TiO2, onto polyimide and parylene C organic substrates are investigated. The layers are grown in a single reactor and the infiltration is performed in a single process, with a resulting nanometric infiltration depth. Mechanical integrity and hermeticity are characterized through tensile fragmentation tests and accelerated aging tests. Flexible Magnesium sensors monitor water vapor permeability in situ. A remarkable improvement in the crack onset strain (∽2.56 times), interfacial shear strength (∽2.1 times), water vapour transmission rate (∽5.2 times) and lifetime performance (∽7.1 times) is achieved, compared to the non‐infiltrated ALD coatings. Pluri‐infiltrated multilayers are proposed as alternatives to conventional coatings. This work is envisioned to accelerate research progress on hermetic packaging of flexible bioelectronics. [ABSTRACT FROM AUTHOR]

Recent studies investigated the hydrolysis of Magnesium (Mg) thin films, highlighting their potential use in biodegradable devices. Quantitatively monitoring the degradation rate and morphological changes of Mg through optical methods and light‐delivery devices offers an innovative, contactless technique, independent of electrical wiring. This method is particularly useful for challenging sensing applications. This study introduces a set of strategies based on Mg optrodes where hydrolysis drives the real‐time monitoring of biofluid penetration through thin‐film encapsulations for bioelectronics. This enables a straightforward assessment of their long‐term reliability, through a quantitative correlation between the water transmission rate (WTR) of the encapsulation and the Mg optical modifications. The optical response of the corroding Mg films deposited on glass substrates and multimode optical fibers tips, within the visible spectrum is characterized. Finally, it is demonstrated that nanopatterning of Mg films as plasmonic nanoantennas significantly enhances the sensitivity of the quantitative approach in the mid‐Infrared spectrum through localized plasmon effects. This method achieves a WTR detection of 6.9 × 10−3 gm−2 day−1 in phosphate buffer solution (25 °C), with a theoretical lower detection limit of ≈10−5 gm−2 day−1. These findings pave the way for the development of a new class of nano‐optical water‐permeation sensors. [ABSTRACT FROM AUTHOR]