To date, numerous biosensing platforms have been developed for assessing drug-induced cardiac toxicity by measuring the change in contractile force of cardiomyocytes. However, these low sensitivity, ...low-throughput, and time-consuming processes are severely limited in their real-time applications. Here, we propose a cantilever device integrated with a polydimethylsiloxane (PDMS)-encapsulated crack sensor to measure cardiac contractility. The crack sensor is chemically bonded to a PDMS thin layer that allows it to be operated very stably in culture media. The reliability of the proposed crack sensor has been improved dramatically compared to no encapsulation layer. The highly sensitive crack sensor continuously measures the cardiac contractility without changing its gauge factor for up to 26 days (>5 million heartbeats), while changes in contractile force induced by drugs are monitored using the crack sensor-integrated cantilever. Finally, experimental results are compared with those obtained via conventional optical methods to verify the feasibility of building a contraction-based drug-toxicity testing system.
Recently developed flexible mechanosensors based on inorganic silicon, organic semiconductors, carbon nanotubes, graphene platelets, pressure-sensitive rubber and self-powered devices are highly ...sensitive and can be applied to human skin. However, the development of a multifunctional sensor satisfying the requirements of ultrahigh mechanosensitivity, flexibility and durability remains a challenge. In nature, spiders sense extremely small variations in mechanical stress using crack-shaped slit organs near their leg joints. Here we demonstrate that sensors based on nanoscale crack junctions and inspired by the geometry of a spider's slit organ can attain ultrahigh sensitivity and serve multiple purposes. The sensors are sensitive to strain (with a gauge factor of over 2,000 in the 0-2 per cent strain range) and vibration (with the ability to detect amplitudes of approximately 10 nanometres). The device is reversible, reproducible, durable and mechanically flexible, and can thus be easily mounted on human skin as an electronic multipixel array. The ultrahigh mechanosensitivity is attributed to the disconnection-reconnection process undergone by the zip-like nanoscale crack junctions under strain or vibration. The proposed theoretical model is consistent with experimental data that we report here. We also demonstrate that sensors based on nanoscale crack junctions are applicable to highly selective speech pattern recognition and the detection of physiological signals. The nanoscale crack junction-based sensory system could be useful in diverse applications requiring ultrahigh displacement sensitivity.
Recent research progress of relieving discomfort between electronics and human body involves serpentine designs, ultrathin films, and extraordinary properties of nanomaterials. However, these ...strategies addressed thus far each face own limitation for achieving desired form of electronic-skin applications. Evenly matched mechanical properties anywhere on the body and imperceptibility of electronics are two essentially required characteristics for future electronic-skin (E-skin) devices. Yet accomplishing these two main properties simultaneously is still very challenging. Hence, we propose a novel fabrication method to introduce kirigami approach to pattern a highly conductive and transparent electrode into diverse shapes of stretchable electronics with multivariable configurability for E-skin applications. These kirigami engineered patterns impart tunable elasticity to the electrodes, which can be designed to intentionally limit strain or grant ultrastretchability depending on applications over the range of 0 to over 400% tensile strain with strain-invariant electrical property and show excellent strain reversibility even after 10 000 cycles stretching while exhibiting high optical transparency (>80%). The versatility of this work is demonstrated by ultrastretchable transparent kirigami heater for personal thermal management and conformal transparent kirigami electrophysiology sensor for continuous health monitoring of human body conditions. Finally, by integrating E-skin sensors with quadrotor drones, we have successfully demonstrated human-machine-interface using our stretchable transparent kirigami electrodes.
Perovskite solar cells have shown unprecedent performance increase up to 22% efficiency. However, their photovoltaic performance has shown fast deterioration under light illumination in the presence ...of humid air even with encapulation. The stability of perovskite materials has been unsolved and its mechanism has been elusive. Here we uncover a mechanism for irreversible degradation of perovskite materials in which trapped charges, regardless of the polarity, play a decisive role. An experimental setup using different polarity ions revealed that the moisture-induced irreversible dissociation of perovskite materials is triggered by charges trapped along grain boundaries. We also identified the synergetic effect of oxygen on the process of moisture-induced degradation. The deprotonation of organic cations by trapped charge-induced local electric field would be attributed to the initiation of irreversible decomposition.
It is certain that perovskite materials must be a game‐changer in the solar industry as long as their stability reaches a level comparable with the lifetime of a commercialized Si photovoltaic. ...However, the operational stability of perovskite solar cells and modules still remains unresolved, especially when devices operate in practical energy‐harvesting modes represented by maximum power point tracking under 1 sun illumination at ambient conditions. This review article covers from fundamental aspects of perovskite instability including chemical decomposition pathways under light soaking and electrical bias, to recent advances and techniques that effectively prevent such degradation of perovskite solar cells and modules. In particular, fundamental causes for permanent degradation due to ion migration and trapped charges are overviewed and explain their interplay between ions and charges. Based on the degradation mechanism, recent advances on the strategies are discussed to slow down the degradation during operation for a practical use of perovskite‐based solar devices.
The operational stability of perovskite solar cells and modules is a key challenge which still remain unresolved. This review article discusses fundamentals of perovskite degradation due to different stresses including air molecules, light illumination, and electrical bias. The operational stability of these devices and recent advances to stabilize devices are overviewed on a way toward commercialization of perovskite solar devices.
Mismatch of current (I)-voltage (V) curves with respect to the scan direction, so-called I–V hysteresis, raises critical issue in MAPbI3 (MA = CH3NH3) perovskite solar cell. Although ferroelectric ...and ion migration have been proposed as a basis for the hysteresis, origin of hysteresis has not been apparently unraveled. We report here on the origin of I–V hysteresis of perovskite solar cell that was systematically evaluated by the interface-dependent electrode polarizations. Frequency (f)-dependent capacitance (C) revealed that the normal planar structure with the TiO2/MAPbI3/spiro-MeOTAD configuration showed most significant I–V hysteresis along with highest capacitance (10–2 F/cm2) among the studied cell configurations. Substantial reduction in capacitance to 10–3 F/cm2 was observed upon replacing TiO2 with PCBM, indicative of the TiO2 layer being mainly responsible for the hysteresis. The capacitance was intensively reduced to 10–5 F/cm2 and C–f feature shifted to higher frequency for the hysteresis-free planar structures with combination of PEDOT:PSS, NiO, and PCBM, which underlines the spiro-MeOTAD in part contributes to the hysteresis. This work is expected to provide a key to the solution of the problem on I–V hysteresis in perovskite solar cell.
Infrared transmission measurements reveal the hybridization of graphene plasmons and the phonons in a monolayer hexagonal boron nitride (h-BN) sheet. Frequency-wavevector dispersion relations of the ...electromagnetically coupled graphene plasmon/h-BN phonon modes are derived from measurement of nanoresonators with widths varying from 30 to 300 nm. It is shown that the graphene plasmon mode is split into two distinct optical modes that display an anticrossing behavior near the energy of the h-BN optical phonon at 1370 cm–1. We explain this behavior as a classical electromagnetic strong-coupling with the highly confined near fields of the graphene plasmons allowing for hybridization with the phonons of the atomically thin h-BN layer to create two clearly separated new surface-phonon-plasmon-polariton (SPPP) modes.
All matter at finite temperatures emits electromagnetic radiation due to the thermally induced motion of particles and quasiparticles. Dynamic control of this radiation could enable the design of ...novel infrared sources; however, the spectral characteristics of the radiated power are dictated by the electromagnetic energy density and emissivity, which are ordinarily fixed properties of the material and temperature. Here we experimentally demonstrate tunable electronic control of blackbody emission from graphene plasmonic resonators on a silicon nitride substrate. It is shown that the graphene resonators produce antenna-coupled blackbody radiation, which manifests as narrow spectral emission peaks in the mid-infrared. By continuously varying the nanoresonator carrier density, the frequency and intensity of these spectral features can be modulated via an electrostatic gate. This work opens the door for future devices that may control blackbody radiation at timescales beyond the limits of conventional thermo-optic modulation.
Double‐walled carbon nanotubes are between single‐walled carbon nanotubes and multiwalled carbon nanotubes. They are comparable to single‐walled carbon nanotubes with respect to the light optical ...density, but their mechanical stability and solubility are higher. Exploiting such advantages, solution‐processed transparent electrodes are demonstrated using double‐walled carbon nanotubes and their application to perovskite solar cells is also demonstrated. Perovskite solar cells which harvest clean solar power have attracted a lot of attention as a next‐generation renewable energy source. However, their eco‐friendliness, cost, and flexibility are limited by the use of transparent oxide conductors, which are inflexible, difficult to fabricate, and made up of expensive rare metals. Solution‐processed double‐walled carbon nanotubes can replace conventional transparent electrodes to resolve such issues. Perovskite solar cells using the double‐walled carbon nanotube transparent electrodes produce an operating power conversion efficiency of 17.2% without hysteresis. As the first solution‐processed electrode‐based perovskite solar cells, this work will pave the pathway to the large‐size, low‐cost, and eco‐friendly solar devices.
Solution‐processed double‐walled carbon nanotubes function as transparent electrodes in inverted‐type planar heterojunction perovskite solar cells. Double‐walled carbon nanotubes exhibit high optical conductivity and solubility. Good energy level alignment and morphology of the electrodes leads to an operating power conversion efficiency of 17.2%, which is the highest among the carbon nanotube electrode‐based perovskite solar cells.
Abstract
The surfactant and colloidal nanoparticles has been considered for various applications because of interaction of both complex mixtures. The hydrophilic SiO
2
nanoparticle could not be ...surface active behavior at the liquid/air interface. In this study, the SiO
2
nanoparticles have been modified with 3-isocyanatopropyltriethoxy-silane (ICP), and the effect of foam stability has been investigated. The physical properties of surface modified SiO
2
nanoparticle were analyzed by XRD, TGA, FT-IR, and SEM. After surface modification of SiO
2
nanoparticles, the contact angle of SiO
2
nanoparticle was also increased from 62° to 82° with increased ICP concentration. The experimental result has shown that SiO
2
nanoparticle with ICP was positive effect and improved foam stability could be obtained at proper ICP concentration compared with un-modified SiO
2
nanoparticle.
PDF
