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Thermal sensations contribute to our ability to perceive and explore the physical world. Reproducing these sensations in a spatiotemporally programmable manner through wireless computer control could enhance virtual experiences beyond those supported by video, audio and, increasingly, haptic inputs. Flexible, lightweight and thin devices that deliver patterns of thermal stimulation across large areas of the skin at any location of the body are of great interest in this context. Applications range from those in gaming and remote socioemotional communications, to medical therapies and physical rehabilitation. Here, we present a set of ideas that form the foundations of a skin-integrated technology for power-efficient generation of thermal sensations across the skin, with real-time, closed-loop control. The systems exploit passive cooling mechanisms, actively switchable thermal barrier interfaces, thin resistive heaters and flexible electronics configured in a pixelated layout with wireless interfaces to portable devices, the internet and cloud data infrastructure. Systematic experimental studies and simulation results explore the essential mechanisms and guide the selection of optimized choices in design. Demonstration examples with human subjects feature active thermoregulation, virtual social interactions, and sensory expansion. [ABSTRACT FROM AUTHOR]

Electrical nerve stimulation serves an expanding list of clinical applications, but it faces persistent challenges in selectively activating bundled nerve ibers. In this study, we investigated electrochemical modulation with an ion-selective membrane (ISM) and whether it, used together with electrical stimulation, may provide an approach for selective control of peripheral nerves. Guided by theoretical transport modeling and direct concentration measurements, we developed an implantable, multimodal ISM cuf capable of simultaneous electrical stimulation and focused Ca2+ depletion. Acutely implanting it on the sciatic nerve of a rat in vivo, we demonstrated that Ca2+ depletion could increase the sensitivity of the nerve to electrical stimulation. Furthermore, we found evidence that the efect of ion modulation would selectively inluence functional components of the nerve, allowing selective activation by electrical current. Our results raise possibilities for improving functional selectivity of new and existing bioelectronic therapies, such as vagus nerve stimulation. [ABSTRACT FROM AUTHOR]

For many peripheral neuro-modulation applications, the cuff electrode has become a preferred technology for delivering electrical current into targeted volumes of tissue. While basic cuffs with low spatial selectivity, having longitudinally arranged contacts, can be produced from relatively straightforward processes, the fabrication of more complex electrode configurations typically requires iterative design and clean-room fabrication with skilled technicians. Although facile methods for fabricating cuff electrodes exist, their inconsistent products have limited their adoption for rapid manufacturing. In this article, we report a fast, low-cost fabrication process for patterning of electrode contacts in an implantable peripheral nerve cuff. Using a laser cutter as we have prescribed, the designer can render precise contact geometries that are consistent between batches. This method is enabled by the use of silicone/carbon black (CB) composite electrodes, which integrate with the patterned surface of its substrate—tubular silicone insulation. The size and features of its products can be adapted to fit a wide range of nerve diameters and applications. In this study, we specifically documented the manufacturing and evaluation of circumpolar cuffs with radial arrays of three contacts for acute implantation on the rat sciatic nerve. As part of this method, we also detail protocols for verification—electrochemical characterization—and validation—electrophysiological evaluation—of implantable cuff electrodes. Applied to our circumpolar cuff electrode, we report favorable electrical characteristics. In addition, we report that it reproduces expected electrophysiological behaviors described in prior literature. No specialized equipment or fabrication experience was required in our production, and we encountered negligible costs relative to commercially available solutions. Since, as we demonstrate, this process generates consistent and precise electrode geometries, we propose that it has strong merits for use in rapid manufacturing. [ABSTRACT FROM AUTHOR]

Abstract Ion selective membrane (ISM) electrodes are widely used for selective ion sensing applications. Recently, new modalities have emerged whose operation involves active electrical polarization of the media, and current theoretical models are unsuitable to predict their behavior beyond near-equilibrium conditions. Here, we apply numerical modeling of physicochemical transport in such systems to study mechanisms of interfacial ion transfer and their role in limiting processes. Importantly, our analysis suggest that membrane-phase complexation (MC) has strong merits as a replacement for interfacial complexation (IC) in theoretical treatments. For our purpose, we have developed a highly detailed model based on Nernst–Planck–Poisson (NPP) with kinetic reactions of first-order. The solutions were derived in terms of logarithmically transformed concentration variables, allowing us to input experimentally determined stability coefficients. A unique process, referred to here as the reaction boundary layer (RBL), is a characteristic of MC, and we found it could have a significant impact on current–voltage (I–V) characteristics and transfer selectivity. Together with other well-known processes such as electrically driven diffusion, the RBL dictates the limits of ISM electrical polarization. Using our model, we demonstrate that operating outside these limits results in ingress of interfering ion species and concurrent loss of transfer selectivity. Highlights • Membrane complexation has strong merits as the intrinsic mechanism of interfacial ion transfer. • A reaction boundary layer effectively produces an intrinsic ISM current limit. • ISM over-limiting processes generally result in loss of transfer selectivity for the primary ion. [ABSTRACT FROM AUTHOR]

Thermal sensations contribute to our ability to perceive and explore the physical world. Reproducing these sensations in a spatiotemporally programmable manner through wireless computer control could enhance virtual experiences beyond those supported by video, audio and, increasingly, haptic inputs. Flexible, lightweight and thin devices that deliver patterns of thermal stimulation across large areas of the skin at any location of the body are of great interest in this context. Applications range from those in gaming and remote socioemotional communications, to medical therapies and physical rehabilitation. Here, we present a set of ideas that form the foundations of a skin-integrated technology for power-efficient generation of thermal sensations across the skin, with real-time, closed-loop control. The systems exploit passive cooling mechanisms, actively switchable thermal barrier interfaces, thin resistive heaters and flexible electronics configured in a pixelated layout with wireless interfaces to portable devices, the internet and cloud data infrastructure. Systematic experimental studies and simulation results explore the essential mechanisms and guide the selection of optimized choices in design. Demonstration examples with human subjects feature active thermoregulation, virtual social interactions, and sensory expansion.