Bidirectional optical response hydrogel with adjustable human comfort temperature for smart windows.

Smart windows are effective in reducing the energy consumption of air conditioning and lighting systems, while contributing to maintaining the comfort zone of temperature in the indoor environment. Currently used smart windows mainly rely on traditional single-phase thermochromic material in which only one abrupt optical change occurs during temperature changes, and their inherent characteristics may not be suited for a practical balance of energy saving and privacy protection. Here, we developed a novel bidirectional optically responsive smart window (BSW) with unique bidirectional optical response features by introducing sodium dodecyl sulfate (SDS)/potassium tartrate (PTH) micelles into PNIPAM hydrogel to form a composite hydrogel, which was encapsulated in two glass panels. The upper critical solution temperature (UCST) and lowest critical solution temperature (LCST) of the material can be individually adjusted and are capable of matching the human comfort zone of temperature. In addition, the smart window exhibits remarkable transparency (92.5%), visible light transmission ratio (Tlum = 91.31%), and excellent solar modulation (ΔTsol,UCST = 76.34%, ΔTsol,LCST = 76.75%). Moreover, it possesses selectivity in transmitting light in the infrared band of solar radiation and can complete the "transparent-opaque" transition in a very narrow temperature range (<1 °C). When at comfortable temperatures, the highly transparent smart windows facilitate interior light and appreciation of the view. At low temperatures, SDS/PTH micelles aggregate to form large micelles, blocking the transmission of light and protecting customer privacy. At high temperatures, PNIPAM can undergo a "sol-gel" transition, thus blocking incident solar radiation. Taken together, these proposed materials with bidirectional optical response characteristics would be harnessed as a promising platform for building energy conservation, anti-counterfeiting, information encryption, and temperature monitoring.

Fronto-parietal theta high-definition transcranial alternating current stimulation may modulate working memory under postural control conditions in young healthy adults.

Objects: This study aimed to investigate the immediate effects of fronto-parietal θ HD-tACS on a dual task of working memory-postural control. Methods: In this within-subject cross-over pilot study, we assessed the effects of 20 min of 6 Hz-tACS targeting both the left dorsolateral prefrontal cortex (lDLPFC) and posterior parietal cortex (PPC) in 20 healthy adults (age: 21.6 ± 1.3 years). During each session, single- and dual-task behavioral tests (working memory single-task, static tandem standing, and a dual-task of working memory-postural control) and closed-eye resting-state EEG were assessed before and immediately after stimulation. Results: Within the tACS group, we found a 5.3% significant decrease in working memory response time under the dual-task following tACS (t = -3.157, p = 0.005, Cohen's d = 0.742); phase synchronization analysis revealed a significant increase in the phase locking value (PLV) of θ band between F3 and P3 after tACS (p = 0.010, Cohen's d = 0.637). Correlation analyses revealed a significant correlation between increased rs-EEG θ power in the F3 and P3 channels and faster reaction time (r = -0.515, p = 0.02; r = -0.483, p = 0.031, respectively) in the dual-task working memory task after tACS. However, no differences were observed on either upright postural control performance or rs-EEG results (p-values <0.05). Conclusion: Fronto-parietal θ HD-tACS has the potential of being a neuromodulatory tool for improving working memory performance in dual-task situations, but its effect on the modulation of concurrently performed postural control tasks requires further investigation.

Transparent, High Stretchable, Environmental Tolerance, and Excellent Sensitivity Hydrogel for Flexible Sensors and Capacitive Pens.

The prospect of ionic conductive hydrogels in multifunctional sensors has generated widespread scientific interest. The new generation of flexible materials should be combined with superior mechanical properties, high conductivity, transparency, sensitivity, good self-restoring fatigue properties, and other multifunctional characteristics, while the current materials are difficult to meet these requirements. Herein, we prepared poly(acrylamide-acrylic acid) (P(AM-AA))/gelatin/glycerol-Al3+ (PG1G2A) ionic conducting hydrogel by one-pot polymerization under UV light. The prepared PG1G2A ionic conductive hydrogel had high tensile strength (539.18 kPa), excellent tensile property (1412.96%), good fast self-recovery and fatigue resistance, high transparency (>80%), excellent moisturizing, and antifreezing/drying properties. In addition, the ionic conductive hydrogel-based strain sensor can respond to mechanical stimulation and generate accurate, stable, and recyclable electrical signals, with excellent sensitivity (GF 5.81). In addition, the PG1G2A hydrogel could be used as flexible wearable devices for monitoring multiple strain and subtle movements of different body parts at different temperatures. Interestingly, the PG1G2A hydrogel capacitive pen embedded in the mold can be used to write and draw on the screen of a phone or tablet. This new multifunctional ionic conducting hydrogel shows broad application prospects in E-skin, motion monitoring, and human-computer interaction in extreme environments.

Network-Based Transcranial Direct Current Stimulation May Modulate Gait Variability in Young Healthy Adults.

Purpose: Previous studies have linked gait variability to resting-state functional connectivity between the dorsal attention network (DAN) and the default network (DN) in the brain. The purpose of this study was to examine the effects of a novel transcranial direct current stimulation (tDCS) paradigm designed to simultaneously facilitate the excitability of the DAN and suppress the excitability of the DN (i.e., DAN+/DN-tDCS) on gait variability and other gait characteristics in young healthy adults. Methods: In this double-blinded randomized and sham-controlled study, 48 healthy adults aged 22 ± 2 years received one 20-min session of DAN+/DN-tDCS (n = 24) or no stimulation (the Sham group, n = 24). Immediately before and after stimulation, participants completed a gait assessment under three conditions: walking at self-selected speed (i.e., normal walking), walking as fast as possible (i.e., fast walking), and walking while counting backward (i.e., dual-task walking). Primary outcomes included gait stride time variability and gait stride length variability in normal walking conditions. Secondary outcomes include gait stride time and length variability in fast and dual-task conditions, and other gait metrics derived from the three walking conditions. Results: Compared to the Sham group, DAN+/DN-tDCS reduced stride length variability in normal and fast walking conditions, double-limb support time variability in fast and dual-task walking conditions, and step width variability in fast walking conditions. In contrast, DAN+/DN-tDCS did not alter average gait speed or the average value of any other gait metrics as compared to the sham group. Conclusion: In healthy young adults, a single exposure to tDCS designed to simultaneously modulate DAN and DN excitability reduced gait variability, yet did not alter gait speed or other average gait metrics, when tested just after stimulation. These results suggest that gait variability may be uniquely regulated by these spatially-distinct yet functionally-connected cortical networks. These results warrant additional research on the short- and longer-term effects of this type of network-based tDCS on the cortical control of walking in younger and older populations.

Stochastic responses of Van der Pol vibro-impact system with fractional derivative damping excited by Gaussian white noise.

This paper focuses on the study of the stochastic Van der Pol vibro-impact system with fractional derivative damping under Gaussian white noise excitation. The equations of the original system are simplified by non-smooth transformation. For the simplified equation, the stochastic averaging approach is applied to solve it. Then, the fractional derivative damping term is facilitated by a numerical scheme, therewith the fourth-order Runge-Kutta method is used to obtain the numerical results. And the numerical simulation results fit the analytical solutions. Therefore, the proposed analytical means to study this system are proved to be feasible. In this context, the effects on the response stationary probability density functions (PDFs) caused by noise excitation, restitution condition, and fractional derivative damping are considered, in addition the stochastic P-bifurcation is also explored in this paper through varying the value of the coefficient of fractional derivative damping and the restitution coefficient. These system parameters not only influence the response PDFs of this system but also can cause the stochastic P-bifurcation.