Highly catalytic Prussian blue analogues and their application on the three-dimensional origami paper-based sweat sensors.

Prussian blue analogues (PBAs) are promising materials due to their rich active sites and straightforward synthesis. However, their limited conductivity and electron transfer inefficiency hinder practical applications. This study utilizes a simple one-pot synthesis approach to produce a tungsten-disulfide (WS2) and iron-cobalt Prussian blue analogue composite (WS2-PBA), enhancing conductivity and electron transfer rate performance. Through the inclusion of sodium citrate into the solution, the S-edge site concentration of WS2 increases. This augmentation introduces additional active sites and defects into the catalyst, enhancing its catalytic activity. The effectiveness of the WS2-PBA 3D-Origami paper device for lactate detection in sweat is also evaluated for biomedical applications. The device demonstrated a robust relationship between the lactate concentration and current intensity (R2 = 0.997), with a detection limit of 1.83 mM. Additionally, this platform has successfully detected lactate in clinical sweat, correlating with the high-performance liquid chromatography test results, suggesting promising prospects for clinical diagnosis. In the future, the excellent catalytic and Rct performance of the WS2-PBA will enable its use in biomedical applications.

Transparent biodegradable composite plastic packaging film from TEMPO-oxidized cellulose nanofibers.

In this research, we develop a method to create biodegradable food packaging films. Initially, TEMPO-oxidized cellulose nanofiber (TOCNF) undergoes sonication to produce well-dispersed single-strain nanofibers. These nanofibers are then blended with waterborne polyurethane (WPU) to enhance their extensibility. To further enhance compatibility between these two components, a non-ionic surfactant, Tween 80, is introduced into the TOCNF/WPU mixture to improve the dispersion of the WPU within the blend. The addition of Tween 80 significantly increases the transparency of the resulting film (Transmittance: 89.4 %, Haze: 2.2 %). Furthermore, the incorporation of the surfactant effectively reduces the formation of wrinkles and cracks during the film drying process, preventing adverse impacts on the film's barrier properties. The thin film further undergoes esterification crosslinking with citric acid to remove its hydrophilic groups for better water vapor barrier properties. The resulting bio-based packaging film exhibits remarkable transparency, strong biodegradability, and superior gas-barrier properties (water vapor and oxygen) compared to commonly used food packaging.

Origami-Inspired Conductive Paper-Based Folded Pressure Sensor with Interconnection Scaling at the Crease for Novel Wearable Applications.

Drawing inspiration from origami structures, a pressure sensor was developed with unique interconnection scaling at its creases crafted on a conductive paper substrate, paving the way for advanced wearable technology. Two screen-printed conductive paper substrates were combined face-to-face, and specific folds were introduced to optimize the sensor structure. The Electrical Contact Resistance (ECR) was systematically analyzed across different fold numbers and crease gaps, revealing a notable trade-off: while increasing the number of folds expanded the sensing area, it also influenced the ECR, reaching a performance plateau. Strategic modifications in the sensor's design, including refining interconnections at the crease, enhanced its sensitivity and stability, culminating in a remarkable sensitivity of 3.75 kPa-1 at subtle pressure levels (0-0.05 kPa). This sensor's real-world applications proved to be transformative, from detecting bruxism and aiding in neck posture correction to remotely sensing trigger finger locking phenomena, highlighting its potential as a pivotal tool in upcoming medical diagnostics and treatments.

A Multimodality Electrochemical and Impedance Spectroscopy System-on-a-Chip With Temperature Sensing and Impedance-Boosting Techniques.

This article presents a multimodal electrochemical sensing system-on-chip (SoC), including the functions of cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and temperature sensing. CV readout circuitry achieves an adaptive readout current range of 145.5 dB through an automatic range adjustment and resolution scaling technique. EIS has an impedance resolution of 9.2 m Ω/√ Hz at a sweep frequency of 10 kHz and an output current of up to 120 µA. With an impedance boost mechanism, the maximum detectable load impedance is extended to 22.95 k Ω, while the total harmonic distortion is less than 1%. A resistor-based temperature sensor using a swing-boosted relaxation oscillator can achieve a resolution of 31 mK in 0-85 °C. The design is implemented in a 0.18 µm CMOS process. The total power consumption is 1 mW.

Conformal Conductive Features on Curvilinear Surfaces with Self-Assembled Silver Nanoplate Thin Films.

In this study, a water transfer method was developed to fabricate conducive thin-film patterns on 3D curvilinear surfaces. Crystalline silver nanoplates (AgNPLs) with a dimension of 700 nm and a thickness of 35 nm were suspended in ethanol with an anionic surfactant, sodium dodecyl sulfate, to improve the suspension stability. The prepared AgNPL suspension was then spread over the water surface via the Langmuir-Blodgett approach to generate a self-assembled thin film. By dipping an accepting object with a robotic arm, the floating AgNPL thin film with nanometer thickness can be effectively transferred to the object surfaces and exhibited a superior conductivity up to 15% of bulk silver without thermal sintering. Besides good conductivity, the AgNPL conductive thin films can also be transferred efficiently on any curvilinear (concave and convex) surface. Moreover, with the help of masks, conductive patterns can be produced on water surfaces and transferred to curvilinear surfaces for electronic applications. As a proof of concept, several examples were demonstrated to display the capability of this approach for radiofrequency identification and other printed circuit applications.

A Brief Review of Graphene-Based Biosensors Developed for Rapid Detection of COVID-19 Biomarkers.

The prevalence of mutated species of COVID-19 antigens has provided a strong impetus for identifying a cost-effective, rapid and facile strategy for identifying the viral loads in public places. The ever-changing genetic make-up of SARS-CoV-2 posts a significant challenfge for the research community to identify a robust mechanism to target, bind and confirm the presence of a viral load before it spreads. Synthetic DNA constructs are a novel strategy to design complementary DNA sequences specific for antigens of interest as in this review's case SARS-CoV-2 antigens. Small molecules, complementary DNA and protein-DNA complexes have been known to target analytes in minimal concentrations. This phenomenon can be exploited by nanomaterials which have unique electronic properties such as ballistic conduction. Graphene is one such candidate for designing a device with a very low LOD in the order of zeptomolar and attomolar concentrations. Surface modification will be the significant aspect of the device which needs to have a high degree of sensitivity at the same time as providing a rapid signaling mechanism.

Skin-Inspired Tactile Sensor on Cellulose Fiber Substrates with Interfacial Microstructure for Health Monitoring and Guitar Posture Feedback.

Skin-inspired flexible tactile sensors, with interfacial microstructure, are developed on cellulose fiber substrates for subtle pressure applications. Our device is made of two cellulose fiber substrates with conductive microscale structures, which emulate the randomly distributed spinosum in between the dermis and epidermis layers of the human skin. The microstructures not only permit a higher stress concentration at the tips but also generate electrical contact points and change contact resistance between the top and bottom substrates when the pressure is applied. Meanwhile, cellulose fibers possessing viscoelastic and biocompatible properties are utilized as substrates to mimic the dermis and epidermis layers of the skin. The electrical contact resistances (ECR) are then measured to quantify the tactile information. The microstructures and the substrate properties are studied to enhance the sensors' sensitivity. A very high sensitivity (14.4 kPa-1) and fast recovery time (approx. 2.5 ms) are achieved in the subtle pressure range (approx. 0-0.05 kPa). The device can detect subtle pressures from the human body due to breathing patterns and voice activity showing its potential for healthcare. Further, the guitar strumming and chord progression of the players with different skill levels are assessed to monitor the muscle strain during guitar playing, showing its potential for posture feedback in playing guitar or another musical instrument.

FT895 Impairs Mitochondrial Function in Malignant Peripheral Nerve Sheath Tumor Cells.

Neurofibromatosis type 1 (NF1) stands as a prevalent neurocutaneous disorder. Approximately a quarter of NF1 patients experience the development of plexiform neurofibromas, potentially progressing into malignant peripheral nerve sheath tumors (MPNST). FT895, an HDAC11 inhibitor, exhibits potent anti-tumor effects on MPNST cells and enhances the cytotoxicity of cordycepin against MPNST. The study aims to investigate the molecular mechanism underlying FT895's efficacy against MPNST cells. Initially, our study unveiled that FT895 disrupts mitochondrial biogenesis and function. Post-FT895 treatment, reactive oxygen species (ROS) in MPNST notably increased, while mitochondrial DNA copy numbers decreased significantly. Seahorse analysis indicated a considerable decrease in basal, maximal, and ATP-production-coupled respiration following FT895 treatment. Immunostaining highlighted FT895's role in promoting mitochondrial aggregation without triggering mitophagy, possibly due to reduced levels of XBP1, Parkin, and PINK1 proteins. Moreover, the study using CHIP-qPCR analysis revealed a significant reduction in the copy numbers of promoters of the MPV17L2, POLG, TFAM, PINK1, and Parkin genes. The RNA-seq analysis underscored the prominent role of the HIF-1α signaling pathway post-FT895 treatment, aligning with the observed impairment in mitochondrial respiration. In summary, the study pioneers the revelation that FT895 induces mitochondrial respiratory damage in MPNST cells.

A Wireless Soil pH and Conductance Monitoring Chip Powered by Soil Microbial and Photovoltaic Energy Cells.

This paper presents an energy-autonomous wireless soil pH and electrical conductance measurement IC powered by soil microbial and photovoltaic energy. The chip integrates highly efficient dual-input, dual-output power management units, sensor readout circuits, a wireless receiver, and a transmitter. The design scavenges ambient energy with a maximal power point tracking mechanism while achieving a peak efficiency of 81.3% and the efficiency is more than 50% over the 0.05-14 mW load range. The sensor readout IC achieves a sensitivity of -8.8 kHz/pH and 6 kHz·m/S, a noise floor of 0.92 x 10-3 pH value, and 1.4 mS/m conductance. To avoid interference, a 433 MHz transceiver incorporates chirp modulation and on-off keying (OOK) modulation for data uplink and downlink communication. The receiver sensitivity is -80 dBm, and the output transmission power is -4 dBm. The uplink data rate is 100 kb/s using burst chirp modulation and gated Class E PA, while the downlink data rate is 10 kb/s with a self-frequency tracking mixer-first receiver.

Total Liquid Transfer with Enhanced Contact Line Slippage.

A new surface treatment method is developed to achieve total liquid transfer. The transfer process of a liquid droplet is recorded through high-speed photography and analyzed via image analysis to investigate the hydrodynamic interactions. For a pristine PMMA surface, a viscous and viscoelastic liquid facilitates transfer by increased viscous and inertial forces and delayed liquid bridge breakage but is limited by slow contact line slippage. Hydrophobic surface treatments can increase contact line slippage and the receding angle to achieve transfer ratios up to 98%. However, pinning and contact angle hysteresis from surface roughness features limit liquid transfer, especially for smaller droplets and higher separation velocities. A lubricant-infused surface treatment with PDMS and a thin layer of less viscous silicone oil provides a smooth, homogeneous surface with fast slippage, low contact angle hysteresis, and only a slight oil wetting ridge. Liquid could then transfer at high ratios (∼99.9%), regardless of droplet size and separation velocity. Finally, complete transfer liquid from indented cells is demonstrated to show the potential of this surface modification method for gravure printing.

Microfluidic wearable electrochemical sweat sensors for health monitoring.

Research on remote health monitoring through wearable sensors has attained popularity in recent decades mainly due to aging population and expensive health care services. Microfluidic wearable sweat sensors provide economical, non-invasive mode of sample collection, important physiological information, and continuous tracking of human health. Recent advances in wearable sensors focus on electrochemical monitoring of biomarkers in sweat and can be applicable in various fields like fitness monitoring, nutrition, and medical diagnosis. This review focuses on the evolution of wearable devices from benchtop electrochemical systems to microfluidic-based wearable sensors. Major classification of wearable sensors like skin contact-based and biofluidic-based sensors are discussed. Furthermore, sweat chemistry and related biomarkers are explained in addition to integration of microfluidic systems in wearable sweat sensors. At last, recent advances in wearable electrochemical sweat sensors are discussed, which includes tattoo-based, paper microfluidics, patches, wrist band, and belt-based wearable sensors.

A novel HDAC11 inhibitor potentiates the tumoricidal effects of cordycepin against malignant peripheral nerve sheath tumor through the Hippo signaling pathway.

Neurofibromatosis type 1 (NF1) is an autosomal dominant neurocutaneous disorder. Clinically, the hallmarks of NF1 include skin pigmentation and cutaneous neurofibroma. Some NF1 patients develop plexiform neurofibroma (PN) since early childhood. Pathologically, PN contains abundant Schwann cells, blood vessels and connective tissues, which may transform into a malignant peripheral nerve sheath tumor (MPNST). MPNST is a highly invasive sarcoma without any effective therapy. Recently, both in vitro and in vivo studies showed that cordycepin can inhibit the growth of MPNST cells. Cordycepin causes cell cycle arrest at G2/M phase and downregulates the protein levels of α-tubulin, p53 and Sp1. Herein, the present study revealed that the HDAC11 inhibitor, FT895, can synergistically enhance the tumoricidal effect of cordycepin against MPNST cells in vitro. Treatment with the combination of cordycepin and FT895 reduced the size of MPNST in the xenograft mouse model. The combined treatment decreased the protein levels of α-tubulin and KIF18A, which may disrupt the microtubule organization leading to the mis-segregation of chromosomes and aneuploidy. Moreover, the expression levels of TEAD1 and its co-activator TAZ, the candidate proteins in hippo signaling pathway, were suppressed after combined treatment. Sequence analysis found a few binding sites for the transcription factor, TEAD1 in the promoter regions of TUBA1B, KIF18A, TEAD1, TAZ, YAP, TP53 and SP1 genes. ChIP-qPCR assay showed that the combined treatment decreases the binding of TEAD1 to the promoters of TUBA1B, KIF18A, TEAD1, TAZ and YAP genes in STS26T cells. The reduced binding to TP53 and SP1 promoters was also found in S462TY cells, which was further confirmed by immunoblotting. The down-regulation of these important transcriptional factors may contribute to the vulnerability of MPNST. In summary, HDAC11 inhibitor, FT895 can potentiate the tumoricidal effect of cordycepin to suppress the MPNST cell growth, which was probably mediated by the dysfunction of hippo-signaling pathway.

Enhancing Stability of High-Concentration ß-Tricalcium Phosphate Suspension for Biomedical Application.

We propose a novel process to efficiently prepare highly dispersed and stable Tricalcium Phosphate (ß-TCP) suspensions. TCP is coupled with a polymer to enhance its brittleness to be used as an artificial hard tissue. A high solid fraction of ß-TCP is mixed with the polymer in order to improve the mechanical strength of the prepared material. The high solid fractions led to fast particle aggregation due to Van der Waals forces, and sediments appeared quickly in the suspension. As a result, we used a dispersant, dispex AA4040 (A40), to boost the surface potential and steric hindrance of particles to make a stable suspension. However, the particle size of ß-TCP is too large to form a suspension, as the gravity effect is much more dominant than Brownian motion. Hence, ß-TCP was subjected to wet ball milling to break the aggregated particles, and particle size was reduced to ~300 nm. Further, to decrease sedimentation velocity, cellulose nanocrystals (CNCs) are added as a thickening agent to increase the overall viscosity of suspension. Besides the viscosity enhancement, CNCs were also wrapped with A40 micelles and increase the stability of the suspension. These CNC/A40 micelles further facilitated stable suspension of ß-TCP particles with an average hydration radius of 244.5 nm. Finally, ß-TCP bone cement was formulated with the suspension, and the related cytotoxicity was estimated to demonstrate its applicability for hard tissue applications.

Exploring the mechanical properties of nanometer-thick elastic films through micro-drop impinging on large-area suspended graphene.

In this work, the dependence of effective Young's modulus on the thickness of suspended graphene was confirmed through a drop impingement method. Large area suspended graphene (LSG) layers with a diameter of up to 400 µm and a nanometer thickness were prepared through transferring chemical vapor deposition grown graphene from copper substrates. 4, 8, and 12-layer LSG samples were found to be crumpled yet defect-free. The mechanical properties of LSG were first studied by observing its interaction with impinging droplets from an ink-jet nozzle. First, the effective Young's modulus was calculated by fitting the instant deformation captured by high speed photography within microseconds. Next, droplets deposited on LSG caused deformation and generated wrinkles and the effective Young's modulus was calculated from the number of wrinkles. The above methods yielded effective Young's modulus values ranging from 0.3 to 3.4 TPa. The results from these methods all indicated that the effective Young's modulus increases with the decreasing thickness or size of suspended graphene layers. Moreover, the crumpled LSG yields higher effective Young's modulus than ideal flat graphene. These comprehensive results from complementary methodologies with precise LSG thickness control down to the nanometer scale provide good evidence to resolve the debate on the thickness dependence of mechanical strength for LSG.

Microwave-Assisted Synthesis for Silver Nanoplates with a High Aspect Ratio.

In this work, a simple and rapid synthesis method was developed to prepare silver nanoplates (AgNPLs) with a high aspect ratio. A microwave heating process with a high heating rate and uniform heating was used to promote the silver reduction reaction. Silver nitrate (AgNO3) was used as the precursor of AgNPLs, and N,N-dimethylformamide (DMF) played the role of a solvent and reducing agent. Poly(vinylpyrrolidone) (PVP) with a molecular weight of 29,000 and a PVP/AgNO3 ratio of 10 were used to control the shape of synthesized AgNPLs. By adjusting the optimal microwave heating parameters, temperature ramping rate, reaction time, and reaction temperature, triangular AgNPLs with high aspect ratios could be produced. The synthesized AgNPLs had an edge length up to 700 nm and a thickness of 35 nm with aspect ratios up to 20. The AgNPLs were also used to produce conductive patterns via pen writing with a conductivity of 2 × 106 S/m to demonstrate the feasibility of applying the synthesized nanomaterials for electronic applications.

Direct Printed Silver Nanowire Strain Sensor for Early Extravasation Detection.

In this study, we presented a wearable sensor patch for the early detection of extravasation by using a simple, direct printing process. Silver nanowire (AgNW) ink was first formulated to provide necessary rheological properties to print patterns on flexible plastic sheets. By adjusting printing parameters, alignments of AgNWs in the printed patterns were controlled to enhance the resistance change under stretching conditions. A resistive strain-sensing device was then fabricated by printing patterned electrodes on a stretchable film for skin attachment. The designed sensor pattern was able to detect forces from a specific direction from the resistance change. Moreover, the sensor showed excellent sensitivity (gauge factor (GF) = 100 at 50% strain) and could be printed in small dimensions. Sensors of millimeter size were printed in an array and were used for multiple detection points in a large area to detect extravasation at small volumes (<0.5 mL) at accurate bump location.

Bio-inspired fractal textile device for rapid sweat collection and monitoring.

In this study, a new design concept in sweat collection was developed to achieve rapid and intact sweat sampling for analytical purposes. Textiles with fast water wicking properties were first selected and laser engraved into tree-like bifurcating channels for sweat collection. The fractal framework of the bifurcating textile channels was theoretically derived to minimize the flow resistance for fast sweat absorption. The optimized collector with designed fractal geometry exhibited thorough coverage of emerging droplets without overflow. Great collection efficiency was achieved with a short induction time (<1 minute after perspiration begins) and a maximum sweat collection flux up to 4.0 µL cm-2 min-1 without leakage. After being combined with printed sensors and microchips, the assembled sweat collection/sensing device can simultaneously provide measurements of salt concentration and sweat rate for wireless hydration state monitoring. The collection/sensing system also exhibited fast response times to abrupt changes in sweat rates or concentrations and thus can be used to detect instant physical conditions in exercise. Finally, field tests were performed to demonstrate the reliability and practicality of the device in real-time sweat monitoring under vigorous activities.

A chemical milling process to produce water-based inkjet printing ink from waste tire carbon blacks.

In this study, a chemical milling process is developed to convert carbon residues from pyrolyzed waste tires into valuable water-based inkjet printing inks. The residues after waste tire pyrolysis were first sieved to remove ash components and ground into powder (~80 µm). The resulting waste tire carbon blacks (TCB) processed by regular dry or wet milling with the help of compatible solvent can only produce particle sizes around 250 nm. To further reduce particle size under the same mechanical energy, aqueous potassium hydroxide was used in the milling process to leach silica in TCB to create loose and vulnerable structure. Moreover, an ionic surfactant, poly (sodium 4-styrenesulfonate) (PSS), was used to decorate the TCB surface and to inhibit particle aggregation. After chemical milling, the PSS/TCB had a primary particle size around 50 nm and a hydraulic diameter around 110 nm. The PSS/TCB suspension possessed a high zeta potential of -73 mV to stably disperse in water for more than 30 days. To help adhesion of the ink on substrates, the PSS/TCB particles were further mixed with waterborne polyurethane (WPU). The WPU/PSS/TCB ink could be inkjet printed into various black patterns, which showed a higher blackness (jetness value = 342.83) than commercial black inks. Moreover, the printed patterns were water-proof and had a pencil scratch hardness of 4H. In summary, this study provides a guideline to convert waste carbon materials into useful printing supplies, and offers a potential application for waste tire recycling.

Multifunctionalized Cellulose Nanofiber for Water-Repellent and Wash-Sustainable Coatings on Fabrics.

A new synthetic route was developed to modify cellulose nanofiber for water-repellent coatings with great sustainability after multiple washing cycles. Multiple functional groups were grafted on 2,2,6,6-tetramethylpiperidine 1-oxyl radical (TEMPO)-oxidized cellulose nanofibers (TOCN) to achieve superhydrophobic performance and strong adhesion on cotton cloth. First, hexadecylamine (HDA) was used to modify TOCN surface into hydrophobic derivatives via amidation. The amidation-modified TOCN (AMT) were then grafted with a polyisocyanate cross-linking agent (PCA). The final multimodified TOCN (MMT) had hydrophobic alkyls and isocyanate groups on the surface. These surface functional groups were confirmed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). After spraying the MMT suspension on cotton fabrics, the isocyanate groups would react with hydroxyl groups on cotton fibers, leading to a uniform conformal layer of MMT on fabric surfaces. The MMT coating showed great water repellence and washing sustainability. A large contact angle of 150° and a small sliding angle of ∼10° were observed. The superhydrophobic performance retained even after 10 laundry washing cycles. Several examples were also demonstrated to show the capability and the possibility of applying this coating material for water-repellent applications.