A Fully Biodegradable Ferroelectric Skin Sensor from Edible Porcine Skin Gelatine

High-performance biodegradable electronic devices are being investigated to address the global electronic waste problem. In this work, a fully biodegradable ferroelectric nanogenerator-driven skin sensor with ultrasensitive bimodal sensing capability based on edible porcine skin gelatine is demonstrated. The microstructure and molecular engineering of gelatine induces polarization confinement that gives rise the ferroelectric properties, resulting in a piezoelectric coefficient (d(33)) of approximate to 24 pC N-1 and pyroelectric coefficient of approximate to 13 mu C m(-2)K(-1), which are 6 and 11.8 times higher, respectively, than those of the conventional planar gelatine. The ferroelectric gelatine skin sensor has exceptionally high pressure sensitivity (approximate to 41 mV Pa-1) and the lowest detection limit of pressure (approximate to 0.005 Pa) and temperature (approximate to 0.04 K) ever reported for ferroelectric sensors. In proof-of-concept tests, this device is able to sense the spatially resolved pressure, temperature, and surface texture of an unknown object, demonstrating potential for robotic skins and wearable electronics with zero waste footprint

Soft and ion-conducting hydrogel artificial tongue for astringency perception

Artificial tongues have been receiving increasing attention for the perception of five basic tastes. However, it is still challenging to fully mimic human tongue-like performance for tastes such as astringency. Mimicking the mechanism of astringency perception on the human tongue, we use a saliva-like chemiresistive ionic hydrogel anchored to a flexible substrate as a soft artificial tongue. When exposed to astringent compounds, hydrophobic aggregates form inside the microporous network and transform it into a micro/nanoporous structure with enhanced ionic conductivity. This unique human tongue-like performance enables tannic acid to be detected over a wide range (0.0005 to 1 wt %) with high sensitivity (0.292 wt %(-1)) and fast response time (similar to 10 s). As a proof of concept, our sensor can detect the degree of astringency in beverages and fruits using a simple wipe-and-detection method, making a powerful platform for future applications involving humanoid robots and taste monitoring devices

Skin-Inspired Hierarchical Polymer Architectures with Gradient Stiffness for Spacer-Free, Ultrathin, and Highly Sensitive Triboelectric Sensors

The gradient stiffness between stiff epidermis and soft dermis with interlocked microridge structures in human skin induces effective stress transmission to underlying mechanoreceptors for enhanced tactile sensing. Inspired by skin structure and function, we fabricate hierarchical nanoporous and interlocked microridge structured polymers with gradient stiffness for spacer-free, ultrathin, and highly sensitive triboelectric sensors (TESs). The skin-inspired hierarchical polymers with gradient elastic modulus enhance the compressibility and contact areal differences due to effective transmission of the external stress from stiff to soft layers, resulting in highly sensitive TESs capable of detecting human vital signs and voice. In addition, the microridges in the interlocked polymers provide an effective variation of gap distance between interlocked layers without using the bulk spacer and thus facilitate the ultrathin and flexible design of TESs that could be worn on the body and detect a variety of pressing, bending, and twisting motions even in humid and underwater environments. Our TESs exhibit the highest power density (46.7 mu W/cm(2)), pressure (0.55 V/kPa), and bending (similar to 0.1 V/degrees) sensitivities ever reported on flexible TESs. The proposed design of hierarchical polymer architectures for the flexible and wearable TESs can find numerous applications in next-generation wearable electronics

Multi‐Layered Triboelectric Nanogenerators with Controllable Multiple Spikes for Low‐Power Artificial Synaptic Devices

Abstract In the domains of wearable electronics, robotics, and the Internet of Things, there is a demand for devices with low power consumption and the capability of multiplex sensing, memory, and learning. Triboelectric nanogenerators (TENGs) offer remarkable versatility in this regard, particularly when integrated with synaptic transistors that mimic biological synapses. However, conventional TENGs, generating only two spikes per cycle, have limitations when used in synaptic devices requiring repetitive high‐frequency gating signals to perform various synaptic plasticity functions. Herein, a multi‐layered micropatterned TENG (M‐TENG) consisting of a polydimethylsiloxane (PDMS) film and a composite film that includes 1H,1H,2H,2H‐perfluorooctyltrichlorosilane/BaTiO3/PDMS are proposed. The M‐TENG generates multiple spikes from a single touch by utilizing separate triboelectric charges at the multiple friction layers, along with a contact/separation delay achieved by distinct spacers between layers. This configuration allows the maximum triboelectric output charge of M‐TENG to reach up to 7.52 nC, compared to 3.69 nC for a single‐layered TENG. Furthermore, by integrating M‐TENGs with an organic electrochemical transistor, the spike number multiplication property of M‐TENGs is leveraged to demonstrate an artificial synaptic device with low energy consumption. As a proof‐of‐concept application, a robotic hand is operated through continuous memory training under repeated stimulations, successfully emulating long‐term plasticity

Ferroelectricity-Coupled 2D-MXene-Based Hierarchically Designed High-Performance Stretchable Triboelectric Nanogenerator

Triboelectric nanogenerators based on the state-of-the-art functional materials and device engineering provide an exciting platform for future multifunctional electronics, but it remains challenging to realize due to the lack of in-depth understanding on the functional properties of nanomaterials that are compatible with microstructural engineering. In this study, a high-performance stretchable (similar to 60% strain) triboelectric nanogenerator is demonstrated via an interlocked microstructural device configuration sandwiched between silvernanowire-(Ag-NW) electrodes and hierarchically engineered spongy thermoplastic polyurethane (TPU) polymer composite with ferroelectric barium-titanate-coupled (BTO-coupled) 2D MXene (Ti3C2Tx) nanosheets. The use of MXene results in an increase in the dielectric constant whereas the dielectric loss is lowered via coupling with the ferroelectricity of BTO, which increases the overall output performance of the nanogenerator. The spongy nature of the composite film increases the capacitance variation under deformation, which results in improved energyconversion efficiency (similar to 79%) and pressure sensitivity (4.6 VkPa-1 and 2.5 mAkPa-1) of the device. With the quantum-mechanically calculated electronic structure, the device converts biomechanical energy to electrical energy and generates an open-circuit output voltage of 260 V, short-circuit output current of 160 mA/m2, and excellent power output of 6.65 W/m2, which is sufficient to operate several consumer electronics. Owing to its superior pressure sensitivity and efficiency, the device enables a broad range of applications including real-time clinical human vital-sign monitoring, acoustic sensing, and multidimensional gesture-sensing functionality of a robotic hand. Considering the ease of fabrication, excellent functionality of the hierarchical polymer nanocomposite, and outstanding energy-harvesting performance of nanogenerators, this work is expected to stimulate the development of next-generation self-powered technology

Stretchable skin hydration sensor based on hygroscopic and ion conductive polymer composites

Transepidermal water loss (TEWL) is water emission from the skin induced by the diffusion of water molecules. Because TEWL is sensitive to damage on the outermost skin layer, it has been utilized as an indicator of skin barrier function. Here, we demonstrate a stretchable hydration sensor to monitor TEWL based on a porous thermoplastic polyurethane (TPU) film coated with ion conductive polyvinyl alcohol (PVA)/lithium chloride (LiCl) composite layers. The stretchable hydration sensor with the large surface area and the hygroscopic PVA/ LiCl layer coated on the porous structure exhibits a remarkable relative current change (Delta I/I0 (%) similar to 107) under a wide humidity range (10-95 % relative humidity (RH)). Moreover, the highly deformable characteristics of the device up to 50 % strain makes it an appropriate tool for detecting water emission from a curved skin surface. For a proof-of-concept demonstration of monitoring skin barrier function, the hydration sensor can precisely perceive the change in TEWL in response to various external treatments (heat, damage, oil treatment, and applying cosmetics). Finally, the stretchable hydration sensor array enables non-contact finger motion perception through water loss detection, making it suitable for use in touchless human-machine interfaces

Magnetic Resonance Imaging-Based Radiomics for the Prediction of Progression-Free Survival in Patients with Nasopharyngeal Carcinoma: A Systematic Review and Meta-Analysis

Advanced non-metastatic nasopharyngeal carcinoma (NPC) has variable treatment outcomes. However, there are no prognostic biomarkers for identifying high-risk patients with NPC. The aim of this systematic review and meta-analysis was to comprehensively assess the prognostic value of magnetic resonance imaging (MRI)-based radiomics for untreated NPC. The PubMed-Medline and EMBASE databases were searched for relevant articles published up to 12 August 2021. The Transparent Reporting of a Multivariable Prediction Model for Individual Prognosis or Diagnosis (TRIPOD) checklist was used to determine the qualities of the selected studies. Random-effects modeling was used to calculate the pooled estimates of Harrell’s concordance index (C-index) for progression-free survival (PFS). Between-study heterogeneity was evaluated using Higgins’ inconsistency index (I2). Among the studies reported in the 57 articles screened, 10 with 3458 patients were eligible for qualitative and quantitative data syntheses. The mean adherence rate to the TRIPOD checklist was 68.6 ± 7.1%. The pooled estimate of the C-index was 0.762 (95% confidence interval, 0.687–0.837). Substantial between-study heterogeneity was observed (I2 = 89.2%). Overall, MRI-based radiomics shows good prognostic performance in predicting the PFS of patients with untreated NPC. However, more consistent and robust study protocols are necessary to validate the prognostic role of radiomics for NPC

Co-solvent induced piezoelectric ??-phase nylon-11 separator for sodium metal battery

Nylon-11, the most studied member of the odd-numbered nylon family, is a promising functional material for future electronic devices or energy storage systems. To utilize nylon-11 in those applications, it is necessary to control the formation of the applicable metastable crystal phases such as the piezoelectric ??-phase or ferroelectric ?????-phase. Herein, we describe a facile method of fabricating metastable ??-phase nylon-11 fibers via electrospinning with a tailored solvent system. By using a solvent mixture of 1,1,1,3,3,3-hexafluoro-2-propanol and trifluoroacetic acid [HFIP:TFA (75:25 mol%)], we could fully eliminate the formation of the most stable ??-phase and create metastable ??-phase nylon-11 fibers. The electrospun ??-phase nylon-11 fibrous membrane displayed a typical piezoelectric response when it experienced a periodic external force. Furthermore, the ??-phase nylon-11 fibrous membrane exhibited higher thermal stability, electrolyte wettability, and ionic conductivity than the conventional Celgard separator. Consequently, it achieved decent performance when applied as a separator in a sodium metal half-cell. This study indicates that piezoelectric ??-phase nylon-11 fibrous membranes have great potential for further development in energy harvesting and storage, especially as piezo-separators in self-charging power cells

Ultra-stretchable yet tough, healable, and biodegradable triboelectric devices with microstructured and ionically crosslinked biogel

To reduce the environmental impact of non-biodegradable electronic waste, developing sustainable technology with biomass-derived biodegradable materials are essential. However, the insufficient mechanical and electrical performances of the conventional biodegradable materials with planar structures often limit their use in bioelectronics. Here, we develop a high-performance ionic biogel device based on three-dimensional (3D) microstructured design of completely healable yet fully biodegradable biogel by using ionically cross-linked biomass resource, gelatin. The stress-absorbing geometry of 3D microstructure improves the mechanical resilience and facilitates highly elastic (similar to 4000%), notch-tolerable and extremely tough (similar to 10,998 J/m(2)) ionic biogels. In addition, the interlocked feature of 3D architecture provides the ionic diode characteristics of the biogel that enhances the triboelectric energy harvesting capability from external stimuli of pressure and temperature, even under an extreme stretching condition. Our triboelectric nanogenerator based on 3D ionic biogels exhibits excellent power output (similar to 325 mW/m(2)), superior energy conversion efficiency (similar to 70.7%) and high-resolution mechano- (similar to 9 Pa) as well as thermo- (similar to 0.03 K) transduction functionalities with long-term stability. The 3D ionic biogel recovers its original electrical properties even after mechanical damage through self-healing. For proof-of-concept demonstrations, the gelatin biogel serve in soft and conformable electronic skins to monitor low-frequency vital signs and high-frequency acoustic waves, for haptic perception of surface textures, and in robotic tactile skins, providing a new benchmark as a clean and green technology for soft bio-electronic devices with zero waste

Ferroelectric Multilayer Nanocomposites with Polarization and Stress Concentration Structures for Enhanced Triboelectric Performances

Although ferroelectric composites have been reported to enhance the performance of triboelectric (TE) devices, their performances are still limited owing to randomly dispersed particles. Herein, we introduce high-performance TE sensors (TESs) based on ferroelectric multilayer nanocomposites with alternating poly(vinylidenefluoride-co-trifluoroethylene) (PVDF-TrFE) and BaTiO3 (BTO) nanoparticle (NP) layers. The multilayers comprising alternating soft/hard layers can induce stress concentration and increase the effective stress-induced polarization and interfacial polarization between organic and inorganic materials, leading to a dielectric constant (17.06) that is higher than those of pure PVDF-TrFE films (13.9) and single PVDF-TrFE/BTO nanocomposites (15.9) at 10 kHz. As a result, the multilayered TESs with alternating BTO NP layers exhibit TE currents increased by 2.3 and 1.5 times compared to pure PVDF-TrFE without BTO NPs and PVDF-TrFE/BTO nanocomposites without multilayer structures, respectively. The multilayered TESs exhibit a high pressure sensitivity of 0.94 V/kPa (48.7 nA/kPa) and output power density of 29.4 mu Wcm(-2), enabling their application in the fabrication of highly sensitive healthcare monitoring devices and high-performance acoustic sensors. The suggested architecture of ferroelectric multilayer nanocomposites provides a robust platform for TE devices and self-powered wearable electronics