Ultra-wide Range Research Articles

An Ion Channel‐Induced Self‐Powered Flexible Pressure Sensor Based on Potentiometric Transduction Mechanism

AbstractGreat efforts have been made to build multifunctional flexible pressure sensing devices to enable future wearable electronics. However, a green‐safe, cost‐effective, self‐powered integrated pressure sensing system remains challenging. Herein, an all‐solid‐state pressure sensing rGM (rGO/GO/PVA nanofibers/MXene) system is designed and developed based on a mechanical potentiometric transduction (MPT) mechanism, which converts mechanical stimulation into the change in the ion transport channel and encodes it into the measured potential difference between two electrodes with hydrated GO, thereby generating potential conduction behavior as well as a programmable stable voltage and current. The self‐powered rGM sensor can yield an output open‐circuit voltage of 0.58 V and a short‐circuit current density of 3.2 µA cm–2 when experiencing a steady mechanical pressure. Unlike typical pressure sensors, rGM sensors have an ultrawide detection range (0.7 Pa–1300 kPa), high stability (maintain 95% performance after 5000 cycles), high adjustability, simple preparation method, implying that the rGM sensor can provide real‐time monitoring for human physiological signals without an external power supply, which has a wide‐range impact on medical care. This work presents a new design based on the MPT mechanism that will significantly simplify manufacturing while improving the performance of future electronic devices and smart systems.

Expanding the Conjugate Structure of Polymeric Carbon Nitride for Enhanced Light Absorption and Photothermal Conversion.

The development of efficient and inexpensive materials for light energy conversion is very important for achieving sustainable energy supply and carbon neutrality. Polymeric carbon nitride has become a promising material for light energy conversion due to its advantages of simple preparation and high physical and chemical stability. However, the pristine polymeric carbon nitride only absorbs light with a wavelength of less than 450nm, and the energy conversion for low-energy photons is very limited. Here, by introducing the pyromellitic dianhydride component to construct an in-plane heterostructure, the conjugated structure of polymeric carbon nitride is successfully expanded. This in-plane carbon nitride-carbon nanoribbon (C3 N4 -C) heterostructure has an ultrawide absorption range from 200 to 2000nm. Compared with the original material, the photothermal conversion performance of C3 N4 -C is significantly improved under the irradiation of Xe lamp or infrared laser. Furthermore, C3 N4 -C exhibits good potential for synergistic photothermal and chemotherapy. This work provides a simple strategy to construct expanded conjugate structure for improved light absorption and energy conversion materials based on polymeric carbon nitride.

Ultrawideband and high-efficient polarization conversion metasurface based on multi-resonant element and interference theory.

In this work, an ultrawideband and high-efficient polarization conversion metasurface (PCM) is proposed, which can efficiently convert linearly polarized waves into cross-polarized waves in an ultra-wide frequency range. The unit cell of the proposed PCM is composed of two pairs of L-shaped metallic patches covered by a dielectric superstrate and an air-based substrate attached with a metallic ground. The PCM has an operating band from 3.37 to 22.07 GHz with the polarization conversion ratio (PCR) over 90% under the normal incidence, which the ratio bandwidth (fH/fL) is 6.5:1. The PCR can achieve 100% at seven resonant frequencies. The equivalent circuit model is analyzed to explain the fundamental cause of the PCM's multi-resonance and polarization conversion behaviors. In addition, all possible near-field interactions among the resonator, the superstrate, and the ground sheet can be accurately calculated using interference theory, which reveals the underlying physical mechanisms of the multi-resonance metasurface. The theoretical calculated, numerically simulated, and measured results are in good agreement. Compared to other PCMs, the proposed PCM has a simple geometry structure but an ultrawideband and high PCR property.

Ferromagnetic Resonance Vector Magnetic Sensor with High Sensitivity and Ultrawide Working Range

AbstractLarge working range is of vital importance for magnetic sensors when exposed to complicated magnetic field profile, especially in automation and power industry where large field variation is frequently encountered. The design for traditional magnetic sensors, e.g., magnetoresistive and fluxgate magnetometers, utilizes ferromagnetic materials with ultrahigh permeability to maximize the field sensitivity, resulting in strictly confined dynamic range due to limited saturation field. Here, an integratable ferromagnetic resonance (FMR) prototype magnetic sensor with high sensitivity and theoretically unlimited working range is reported. An ultrawide working range (>450 mT) which is more than two orders larger than that of commercial sensors with similar field resolution is experimentally verified. Moreover, the FMR magnetometer is a vector sensor in contrast to the traditional scalar sensors based on magnetic resonance. With a navigating magnetic field of 50 μT (ca. the Earth's magnetic field), the resolution for azimuth angle is 0.006°. Compared with traditional nuclear magnetic resonance and electron paramagnetic resonance sensors with large size and high power consumption, the compact FMR sensor with large dynamic range and high sensitivity has much broader application prospects, especially in magnetically harsh environments.

Towards optimization of plant cell detection in suspensions using impedance-based analyses and the unified equivalent circuit model

An improved approach for comparative study of plant cells for long term and continuous monitoring using electrical impedance spectroscopy is demonstrated for tomato and tobacco plant cells (MSK8 and BY2) in suspensions. This approach is based on the locations and magnitudes of defining features in the impedance spectra of the recently reported unified equivalent circuit model. The ultra-wide range (4 Hz to 20 GHz) impedance spectra of the cell lines were measured using custom probes, and were analyzed using the unified equivalent circuit model, highlighting significant negative phase peaks in the ~ 1 kHz to ~ 10 MHz range. These peaks differ between the tomato and tobacco cells, and since they can be easily defined, they can potentially be used as the signal for differentiating between different cell cultures or monitoring them over time. These findings were further analysed, showing that ratios relating the resistances of the media and the resistance of the cells define the sensitivity of the method, thus affecting its selectivity. It was further shown that cell agglomeration is also an important factor in the impedance modeling in addition to the overall cell concentration. These results can be used for optimizing and calibrating electrical impedance spectroscopy-based sensors for long term monitoring of cell lines in suspension for a given specific cell and media types.

Nanostructural evolution of Al(OH)3 gel formed by the cubic and orthorhombic ye'elimite clinkers of calcium sulfoaluminate cements in an ultra-wide hydration temperature range

This paper investigated the influence of hydration temperature on the nanostructure of the AH3 phase formed in calcium sulfoaluminate cements. Orthorhombic ye'elimite (st-ye'elimite) and cubic ye'elimite (ss-ye'elimite) were hydrated in an ultra-wide temperature range (5–220 °C). Results showed that the AH3 phase formed by ss-ye'elimite was always microcrystalline in nature at various curing temperatures (5–130 °C), and transformed into the AlOOH phase at 150 °C and above. However, the AH3 phase formed by st-ye'elimite grew from a microcrystal to a favorable crystal as the temperature increased, and transformed into the AlOOH phase at 170 °C and above. The nanostructure of hydration products was further investigated using TEM/SAED analysis together with FE-SEM images, directly evidencing that the formed AFm-12 phase was single-crystal in nature, and the formed AH3 phase was microcrystalline at low temperatures and grew into single-crystal hexagonal prisms with the preferred growth direction along [001] direction at high temperatures.

A Surface-Confined Gradient Conductive Network Strategy for Transparent Strain Sensors toward Full-Range Monitoring

The development of transparent and flexible sensors suitable for the full-range monitoring of human activities is highly desirable, yet presents a daunting challenge due to the need for a combination of properties such as high stretchability, high sensitivity, and good linearity. Gradient structures are commonly found in many biological systems and exhibit excellent mechanical properties. Here, we report a novel surface-confined gradient conductive network (SGN) strategy to construct conductive polymer hydrogel-based stain sensors (CHSS). This CHSS showed an ultrahigh stretchability of 4000% strain, transparency above 90% at a wavelength of 600 nm, as well as skin-like Young's modulus of 40 kPa. Impressively, the sensitivity was improved to 3.0 and outstanding linear sensing performance was achieved simultaneously in the ultrawide range of 0% to 4000% strain with a high R-square value of 0.994. With the help of SGN strategy, this CHSS was able to monitor both large-scale and small-scale human motions and activities. This SGN strategy can open a new avenue for the development of novel flexible strain sensors with excellent mechanical, transparent, and sensing performance for full-range monitoring of human activities.

Prospects and challenges of colloidal quantum dot laser diodes

Colloidal quantum dots (QDs) combine the superior light-emission characteristics of quantum-confined semiconductors with the chemical flexibility of molecular systems. These properties could, in principle, enable solution-processable laser diodes with an ultrawide range of accessible colours. However, the realization of such devices has been hampered by fast optical gain decay due to non-radiative Auger recombination and poor stability of QD solids at the high current densities required for the lasing regime. Recently, these problems have been resolved, which resulted in the development of electrically pumped optical gain devices operating at ultrahigh current densities of around 1,000 A cm−2. The next step is the realization of a QD laser diode (QLD). Here we assess the status of the QD lasing field, examine the remaining challenges on the path to a QLD and discuss practical strategies for attaining electrically pumped QD lasing. Colloidal quantum dots may offer solution-processable lasers, with a wide range of colours available. Technical hurdles and progress towards realization of useful quantum dot laser diodes is reviewed.

Design of ultra-broadband absorption enhancement in plasmonic absorber by interaction resonance of multi-plasmon modes and Fabry-Perot mode

This paper shows a strategy to realize ultra-broadband absorption of multi-spectral coverage. A vertical cascaded plasmonic absorber constructed by multilayer helical metallic nanostructure wrapped in a pyramid-shaped dielectric jacket is presented and investigated by numerical simulations. By premeditated planning of the scale proportions of the spirals and the dimension size of the pyramid-shaped dielectric, more than 90% of absorption is realized in 189-3896 nm, an ultra-wide spectral range that basically covers the bands of near-ultraviolet, visible light, and near-infrared. The excitation mechanism of electromagnetic resonance and the formation process of light trapping are both included in the investigation through the analysis of electromagnetic field distribution. The localized surface plasmon mode in the metallic nano-spiral and the Fabry-Perot cavity mode with the gap plasmon resonance in the dielectric gap cooperatively make a significant contribution to reduce the reflection and form the ultra-broadband absorption. The simulation results show that the proposed absorber is basically insensitive to the incident angle and polarization angle, which basically keeps more than 90% absorption within the incident angle of ± 80 °. Such a specific implementation idea can also be applied to the terahertz region by modifying the geometrical size of the structure. This presented design implies new viability to develop the broadband photodetectors, solar cells, and thermal emitters.

Broadband diffuse field sound insulation of double layer metamaterial plates lined with porous material

We propose a composite acoustic metamaterial consisting of double layer metamaterial plates (DLMPs) lined with porous material (PM). Numerical results show that DLMPs lined with PM can produce a very high diffuse field sound transmission loss (STL) beyond the mass law over an ultra-wide low-frequency range. The unusual behavior is interpreted by explicit formulas. For validation, a large-scale specimen is fabricated using light surface mass density (5.72 kg/m2) and small thickness (5 cm). Measured data show that the specimen possesses an excellent diffuse field STL deeply breaking the mass law at broadband low frequencies (248–1624 Hz), and simultaneously, it has an improved diffuse field STL within a wide low-frequency band (208–850 Hz) compared with the conventional double layer homogeneous plates lined with PM. Owing to the simple construction, light weight, and thinness, the proposed composite metamaterial has promising applications in noise control engineering.

A Portable Ultrawideband Confocal Raman Spectroscopy System with a Handheld Probe for Skin Studies.

Confocal Raman spectroscopy (CRS) has shown potential in non-invasive skin analysis. However, current CRS systems have various limitations including a narrow detection band, large size, non-flexibility, slowness, and complexity, which hinder their clinical applications. Herein, we developed a portable ultrawideband CRS system with a fiber-based handheld probe to acquire the Raman spectra in both fingerprint and high wavenumber regions in a fast and quasi-simultaneous way. Dual-wavelength excitation with a dual-passband laser cleaning filter and high-speed fiber array multiplexer was adopted instead of a specialized grating and detector to achieve instant switching between the detection regions and improve system robustness. Preliminary in vivo results demonstrated its depth profiling capability in an ultrawide detection range for stratum corneum thickness, natural moisturizing factor, and water content quantification, indicating its great potential in a wide range of clinical and cosmeceutical applications.

High breakdown strength and enhanced energy storage performance of niobate-based glass-ceramics via glass phase structure optimization

The dielectric capacitors with excellent energy storage characteristics, high power density and temperature stability are strongly desired in modern pulse power system and electronic industry. Thus, BKNAS-xPbO glass-ceramics were designed and prepared. Free oxygen in the glass phase which weakens the glass network structure can be adsorbed by trace Pb2+, thus improving the breakdown strength (BDS) of BKNAS glass-ceramics. Extremely high BDS (~2089 kV/cm) and excellent energy storage density (~17.62 J/cm3) were achieved in 0.6 mol% PbO doped BKNAS glass-ceramics. Moreover, the permittivity variance of BKNAS-0.6PbO glass-ceramics was less than 4.39% in the ultrawide temperature range (−80–300 °C), suggesting excellent temperature stability. The single layer capacitor made by BKNAS-0.6PbO glass-ceramics also exhibited excellent charge-discharge performance, in which the underdamped discharge power density reached 133.69 MW/cm3 as well as the overdamped discharge power density reached 146.89 MW/cm3 with ultrashort discharge time (<18 ns). The above results show that BKNAS-0.6PbO glass-ceramics possesses great potentiality for pulse capacitors owning to excellent energy storage property, temperature stability and charge-discharge performance.

Ultra-wide frequency tuning range for optical properties in coaxial quantum well driven by intense laser field

A new approach for controlling intersubband transitions and optical properties of coaxial cylindrical quantum well is proposed. Considering the correct dressing effect for the confinement potential, the new ultra-wide tuning mechanism is based on the variation of quasibound states with the intensity of long-wavelength laser field. By means of the finite difference method, the results provide a new explanation for the anticrossing of energy levels and exhibit great potential for ultra-wide frequency tunability (ranging from terahertz to the mid-infrared region) of the optical absorption coefficient and refractive index changes by modulating the laser parameters and barrier thickness.

Temperature stable (1-x)(0.9Na0.5Bi0.5TiO3-0.1BiAlO3)-xNaTaO3 ceramics and capacitors with ultra-wide operational range

Temperature stable multilayer ceramic capacitors (MLCCs) are urgently required for electronic equipment applications. In this work, NaTaO3 modified (1-x)(0.9Na0.5Bi0.5TiO3-0.1BiAlO3) ceramics (NBT-10BA-100xNT) were designed and fabricated. The effects of NaTaO3 concentration on the dielectric properties, insulating properties, and energy storage properties were investigated. At the optimum composition of x = 0.25, stable permittivity (Δε′/ε25°C′≤±15%) and low dielectric loss (tanδ≤ 0.02) over a wide temperature range of −100–334 °C were achieved. Furthermore, NBT-10BA-25NT based MLCCs with 70Ag/30 Pd inner electrodes were successfully fabricated by tape-casting method, which also exhibited both stable permittivity (Δε′/ε25°C′≤±15%) and low dielectric loss (tanδ ≤ 0.02) in an ultra-wide temperature range (−100–398 °C). These excellent performances suggest that NBT-10BA-25NT could be a promising candidate of dielectrics with ultra-wide operational temperature range for MLCCs.

Perovskite-SrTiO3/TiO2/PDA as photoelectrochemical glucose biosensor

The complexity of the biological sample to be tested requires the sensor to have a wide monitoring range, accurate selectivity, and excellent environmental tolerance. Here, we report a new strategy of in situ transformation of perovskite to form a heterojunction and combined with bioactive enzyme protective substances, thereby achieving a collection of multiple sensing properties. Through in situ conversion of TiO2 to SrTiO3 to form a heterojunction to provide high oxidation activity and protection for GOx through PDA, the TiO2/SrTiO3/PDA/GOx biosensor achieves an ultra-wide linear detection range of 0–32 mM. Such a range can effectively monitor the physical condition of people with high blood sugar levels (above 20 mM). Good stability, anti-interference, environmental tolerance, and accurate human blood detection all prove the excellent sensing performance and practical application potential of the TiO2/SrTiO3/PDA/GOx biosensor.

Channel-Crack-Designed Suspended Sensing Membrane as a Fully Flexible Vibration Sensor with High Sensitivity and Dynamic Range.

Vibration sensors are essential for signal acquisition, motion measuring, and structural health evaluations in civil and industrial applications. However, the mechanical brittleness and complicated installation process of micro-electromechanical system vibration sensors block their applications in wearable devices and human-machine interaction. The development of flexible vibration sensors satisfying the requirements of good flexibility, high sensitivity, and the ability to attach conformably on curved critical components is highly demanded but still remains a challenge. Here, we demonstrate a highly sensitive and fully flexible vibration sensor with a channel-crack-designed suspended sensing membrane for high dynamic vibration and acceleration monitoring. The flexible sensor is designed as a suspended vibration membrane structure by bonding a channel-crack-sensing membrane on a cavity substrate, of which the suspended sensing membrane can freely vibrate out of plane under external vibration. By inducing the cracks to be generated in the embedded multiwalled carbon nanotube channels and fully cracked across the conducting routes, the suspended vibration membrane shows high sensitivity, good reproducibility, and robust sensing stability. The resultant vibration sensor demonstrates an ultrawide frequency vibration response range from 0.1 to 20,000 Hz and exhibits the ability to respond to acceleration vibration with a broad response of 0.24-100 m/s2. The high sensitivity, wide bandwidth, and fully flexible format of the vibration sensor enable it to be directly attached on human bodies and curvilinear surfaces to conduct in situ vibration sensing, which was demonstrated by motion detection, voice identification, and the vibration monitoring of mechanical equipment.

All range highly linear and sensitive humidity sensor based on 2D material TiSi2 for real-time monitoring

Nowadays, two-dimensional (2D) materials with layered structures, known as transition metal dichalcogenides (TMDCs), are highly appealing in humidity sensing applications. Herein, the humidity sensor based on the 2D material titanium disillicide (TiSi2) is exploited for the first time with high sensing performances for the continuous monitoring of various human interactive activities such as breath monitoring and contactless skin humidity sensing. It proposes a highly sensitive humidity sensor with excellent all range linear humidity sensing performance through printed technologies. Inter-digital electrodes (IDEs) are fabricated through a screen printing process, and the 2D TiSi2 the active layer is coated on the electrodes through the spin-coating process. Furthermore, the TiSi2 ink is prepared through a wet grinding process to achieve the 2D nano-flakes. The proposed sensor has a decent linear response over an ultra-wide detection range of (0 %–100 %) RH with a fast transient response of 0.9 s and 8 s for impedance while 3 s and 4 s for capacitance. The sensor shows high impedance sensitivity of 63 kΩ / %RH at 1 kHz, having good stability for 360 min. Hence, the fabricated sensor also showed fast response and sensitivity towards various real-time applications such as water spraying test, and real time monitoring. These outstanding performances of the proposed sensor can open new horizons for the variety of humidity sensing applications.

A portable droplet generation system for ultra-wide dynamic range digital PCR based on a vibrating sharp-tip capillary

Monodisperse droplet has been widely used as a versatile tool in different disciplines including biosensing. Existing methods still struggle to balance the droplet generation performance with system simplicity. Here we introduce a novel droplet generation scheme based on the acoustic streaming generated from a vibrating sharp-tip capillary. The unique fluid pattern enables efficient droplet generation without any external pressure sources. This method achieved real-time modulation of droplet size over an ultra-wide range (6.77–661 μm), high throughput (up to 5000 droplets/s), and good monodispersity (<4%) with a power consumption below 60 mW. This method has enabled a multi-volume digital PCR with a dynamic range of ~6 orders of magnitude and multiplexing capability. It has also enabled a simple protocol to produce cell-laden alginate microcapsules in variable sizes with excellent biocompatibility. Overall, the present method combines high performance with small footprint and portability, which will be especially valuable for droplet applications requiring variable droplet size and performed in resource-limited settings.

Vibration characteristics of innovative reentrant-chiral elastic metamaterials

In this work, an innovative two-dimensional (2D) hybrid auxetic elastic metamaterial (MODEL I) with reentrant triangular and chiral structures is proposed to open the broaden bandgap for vibration attenuation. Furthermore, the hybrid reentrant-chiral lattice with embedded resonators (MODEL II) shows multiple bandgaps at ultra-low frequency. Based on theoretical lumped mass-in-mass method and finite element method, the bandgap and longitudinal elastic wave attenuation are characterized. There is no complete bandgap in classical reentrant triangular lattice (MODEL 0), while the complete bandgaps width for MODEL I and II account for one forth of the concerned frequency range (0–4500 Hz). What more, the lower boundary of the first bandgap for MODEL II is 56% lower than that of MODEL I. The bandgap formation mechanisms are investigated by analyzing the mode shapes on the dispersion curves, and the frequency-dependent energy flow are studied through the iso-frequency contours, phase and group velocities. Finally, the longitudinal elastic wave attenuation of finite-size lattice of MODEL II illustrates ultra-wide vibration attenuation frequency range in the directional bandgaps. This research provides important clues and theoretical guidance for the design of vibration isolators, beam, plates and other renewed devices.

Multifunctional polypyrrole and rose-like silver flower-decorated E-textile with outstanding pressure/strain sensing and energy storage performance

Textile-based wearable devices have attracted much attention as they can improve the wearing comfort and safety of electronic products. This paper proposes a fabrication strategy for a multifunctional e-textile based on polypyrrole (PPy) and rose-like silver flower-decorated knitted cotton/spandex fabric (KCSF). The rose-like silver flower grown on the PPy surface by electrodeposition can further improve the surface roughness and pressure sensitivity of the fabric. PPy and rose-like silver flower-decorated KCSF can be used to construct a multi-layer pressure/strain sensor. The as-obtained sensor not only exhibits an ultra-wide working pressure range (0–900 kPa), but also achieves a high sensitivity (17.41 kPa−1 for low-pressure areas), which effectively balances the operating range and sensitivity. More importantly, the sensor can be used to accurately monitor different physiological signals, including the levels of swallowing, breathing rate, voice recognition, and sleep quality. In addition, an all-solid-state supercapacitor is fabricated using PPy-coated fabric electrodes, demonstrating a high areal capacitance of 978.9 mF cm−2 at 1 mA cm−2, an energy density of 80.3 µWh cm−2, and power density of 0.38 mW cm−2. The multifunctional e-textile with excellent sensing and energy storage behaviors is simple and easy to manufacture, with potential application prospects in the broad field of wearable technology.