Intrinsically stretchable and transparent thin-film transistors based on printable silver nanowires, carbon nanotubes and an elastomeric dielectric.

Thin-film field-effect transistor is a fundamental component behind various mordern electronics. The development of stretchable electronics poses fundamental challenges in developing new electronic materials for stretchable thin-film transistors that are mechanically compliant and solution processable. Here we report the fabrication of transparent thin-film transistors that behave like an elastomer film. The entire fabrication is carried out by solution-based techniques, and the resulting devices exhibit a mobility of ∼30 cm(2) V(-1) s(-1), on/off ratio of 10(3)-10(4), switching current >100 μA, transconductance >50 μS and relative low operating voltages. The devices can be stretched by up to 50% strain and subjected to 500 cycles of repeated stretching to 20% strain without significant loss in electrical property. The thin-film transistors are also used to drive organic light-emitting diodes. The approach and results represent an important progress toward the development of stretchable active-matrix displays

From GPT-4 to Gemini and Beyond: Assessing the Landscape of MLLMs on Generalizability, Trustworthiness and Causality through Four Modalities

Multi-modal Large Language Models (MLLMs) have shown impressive abilities in generating reasonable responses with respect to multi-modal contents. However, there is still a wide gap between the performance of recent MLLM-based applications and the expectation of the broad public, even though the most powerful OpenAI's GPT-4 and Google's Gemini have been deployed. This paper strives to enhance understanding of the gap through the lens of a qualitative study on the generalizability, trustworthiness, and causal reasoning capabilities of recent proprietary and open-source MLLMs across four modalities: ie, text, code, image, and video, ultimately aiming to improve the transparency of MLLMs. We believe these properties are several representative factors that define the reliability of MLLMs, in supporting various downstream applications. To be specific, we evaluate the closed-source GPT-4 and Gemini and 6 open-source LLMs and MLLMs. Overall we evaluate 230 manually designed cases, where the qualitative results are then summarized into 12 scores (ie, 4 modalities times 3 properties). In total, we uncover 14 empirical findings that are useful to understand the capabilities and limitations of both proprietary and open-source MLLMs, towards more reliable downstream multi-modal applications

Optimizing the Configuration and Control of a Novel Human-Powered Energy Harvesting System

Abstract—As sensor equipped wearable systems enter the mainstream, system longevity and power-efficiency issues hamper large scale and long-term deployment, despite substantial foreseeable benefits. As power and energy efficient design, sampling, processing and communication techniques emerge to counter these issues, researchers are beginning to look on wearable energy harvesting systems as an effective counterpart solution. In this paper, we propose a novel harvesting technology to inconspicuously transduce mechanical energy from human foot-strikes and power low-power wearable systems in a self-sustaining manner. Dielectric Elastomers (DEs) are high-energy density electrostatic transducers that can transduce significant levels of energy from a user while appearing near-transparent to her, if configured and controlled properly. Towards this end, we propose DE-based harvester configuration that capitalizes on properties of human gait to enhance transduction efficiency, and further leverage these properties in an adaptive control algorithm to optimize the net energy produced by the system. We evaluate system performance from detailed analytical and empirical models of DE transduction behavior, and apply our control algorithm to the modeled DEs under experimentally collected foot pressure datasets from multiple subjects. Our evaluations show that the proposed system can achieve up to 120mJ per foot-strike, enough to power a variety of low-power wearable devices and systems. I

Driving low-power wearable systems with an adaptively-controlled foot-strike scavenging platform

We explore the use of Dielectric Elastomer (DE) microgenerators as a means to scavenge energy from foot-strikes and power wearable systems. While they exhibit large energy densities, DEs must be closely controlled to maximize the energy they transduce. Towards this end, we propose a DE micro-generator array configuration that enhances transduction efficiency, and the use of foot pressure sensors to realize accurate control of the individual DEs. Statistical techniques are applied to customize performance for a user’s gait and enable energy-optimized adaptive online control of the system. Simulations based on experimentally collected foot pressure datasets, empirical characterization of DE mechanical behavior and a detailed model of DE electrical behavior show that the proposed system can achieve between 45 and 66mJ per stride

1 Optimizing the Output of a Human-Powered Energy Harvesting System with Miniaturization and Integrated Control

Abstract—We propose a novel harvesting technology to inconspicuously transduce mechanical energy from human foot-strikes and explore its configuration and control towards optimized energy output. Dielectric Elastomers (DEs) are high-energy density, soft, rubber-like material that electrostatically transduce mechanical energy. These properties enables increased energy-transduction efficiency without sacrificing on user comfort, if configured and controlled properly. We expose key statistical properties of human gait which show that an array of miniaturized harvesters across the foot-sole will improve energy output. Further, the gait properties naturally yield a closed-loop control strategy to individually control harvesters in the array in a manner that maximizes net energy output. We propose statistical techniques that guide the configuration and control of the harvester array, and evaluate system behavior from detailed analytical and empirical models of DE behavior. System evaluations based on experimentally collected foot pressure datasets from multiple subjects show that the proposed system can achieve up to 120mJ per foot-strike, enough to power a variety of low-power wearable devices and systems. I

Singularity engineering of the resonant perfect absorber

The metal-dielectric-metal (MDM) perfect absorber (PA) is an important kind of resonant metasurface with promising applications in selective thermal emitting, solar energy harvesting, biosensing and so on. Establishing a direct link between resonant features and structural parameters is essential for guiding design processes and exploring novel applications. In this paper, we conduct a comprehensive investigation of the MDM PA, utilizing scattering singularity (pole/zero) engineering. We propose a straightforward design methodology to achieve a MDM PA operating at a specific wavelength, and demonstrate a design example with a maximum absorption of 99.93 % at 1200 nm and a full width of half maximum of about 155 nm, which is subsequently experimentally validated. The results indicate high absorption across a wide range of angles. This study sheds new light on fast design and analysis of MDM PAs

Kinetic Hydrate Inhibition of Natural Gels in Complex Sediment Environments

Natural gels are emerging as a hotspot of global research for their greenness, environmental-friendliness, and good hydrate inhibition performance. However, previous studies mostly performed experiments for simple pure water systems and the inhibition mechanism in the sediment environment remains unclear. Given this, the inhibition performance of xanthan gum and pectin on hydrate nucleation and growth in sediment environments was evaluated via hydrate formation inhibition tests, and the inhibition internal mechanisms were revealed via a comprehensive analysis integrating various methods. Furthermore, the influences of natural gels on sediment dispersion stability and low-temperature fluid rheology were investigated. Research showed that the sediments of gas hydrate reservoirs in the South China Sea are mainly composed of micro-nano quartz and clay minerals. Xanthan gum and pectin can effectively inhibit the hydrate formation via the joint effects of the binding, disturbing, and interlayer mass transfer suppression processes. Sediments promote hydrate nucleation and yet inhibit hydrate growth. The interaction of sediments with active groups of natural gels weakens the abilities of gels to inhibit hydrate nucleation and reduce hydrate formation. Nonetheless, sediments help gels to slow down hydrate formation. Our comprehensive analysis pointed out that pectin with a concentration of 0.5 wt% can effectively inhibit the hydrate nucleation and growth while improving the dispersion stability and low-temperature rheology of sediment-containing fluids

Green process of biomass waste derived fluorescent carbon quantum dots for biological imaging in vitro and in vivo

International audienceIn the context of the circular economy, the huge amounts of biomass waste should be converted into value-added materials and energy to diminish pollution, atmospheric CO2 levels and costly waste disposal. Biological imaging usually uses expensive and toxic chemicals e.g. , organic dyes, semiconductor quantum dots, calling for safer, greener, cheaper fluorescent probes for biological imaging in vitro and in vivo. In these regards, carbon quantum dots (CQDs)-based fluorescent probes using biomass waste as a precursor may have much higher potential. Here we transformed the biomass waste of peach leaves into value-added fluorescent CQDs through a low-cost and green one-step hydrothermal process. The obtained CQDs show excitation-dependent photoluminescence properties with a fluorescence lifetime of 5.96 ns and a quantum yield of 7.71% without any passivation. In addition, the CQDs have a fine size of 1.9 nm with good hydrophilicity and high fluorescent stability over pH 4.0–11.0 range. Fluorescence imaging of in vitro cell cultures and in vivo with zebrafish show that CQDs possess ultra-low toxicity and remarkable performance for biological imaging. Even when CQDs present at a concentration as high as 500 μg/mL, the organism can still maintain more than 90% activity both in vitro and in vivo , and present bright fluorescence. The cheaper, greener, ultra-low toxicity CQDs developed in this work is a potential candidate for biological imaging in vitro and in vivo

Phase-Changing Bistable Electroactive Polymer Exhibiting Sharp Rigid-to-Rubbery Transition

A phase-changing polymer comprising stearyl acrylate and a long-chain urethane diacrylate was studied as a new bistable electroactive polymer. The abrupt and reversible phase transition of the crystalline aggregates of the stearyl moieties results in a rapid shift between the rigid and rubbery states of the polymers during temperature cycles. The transition temperature is tunable between 34–46 °C. A storage modulus change of ∼1000 fold can be obtained within a narrow temperature range of 10 °C. The polymer shows excellent shape memory properties with both fixation rate and recovery rate close to 100%. Diaphragm actuators based on the polymer thin films were electrically actuated up to 70% strain at 50 °C. The actuated shape can be “frozen” after the films were allowed to cool below the transition temperature. This rigid-to-rigid deformation is refreshable and repeatable via the rigid-to-rubbery transition and electrical actuation in the rubbery state