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.

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.

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.

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.

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.

Highly Responsive PEG/Gold Nanoparticle Thin-Film Humidity Sensor via Inkjet Printing Technology.

In this study, a highly responsive humidity sensor is developed by printing gold nanoparticles (GNPs) grafted with a hygroscopic polymer. These GNPs are inkjet-printed to form a uniform thin film over an interdigitated electrode with a controllable thickness by adjusting the printing parameters. The resistance of the printed GNP thin film decreases significantly upon exposure to water vapor and exhibits a semi-log relationship with relative humidity (RH). The sensor can detect RH variations from 1.8 to 95% with large resistance changes up to 4 orders of magnitude with no hysteresis and small temperature dependence. In addition, with a small thickness, the sensor can reach absorption equilibrium quickly with response and recovery times of ≤1.2 and ≤3 s, respectively. The fast response to humidity changes also allows the GNP thin-film sensor to distinguish signals from intermittent humidification/dehumidification cycles with a frequency up to 2.5 Hz. The printed sensors on flexible substrates show little sensitivity to bending deformation and can be embedded in a mask for human respiratory detection. In summary, this study demonstrates the feasibility of applying printing technology for the fabrication of thin-film humidity sensors, and the methodology developed can be further applied to fabricate many other types of nanoparticle-based sensor devices.

Welding Silver Nanowire Junctions for Transparent Conducting Films by a Rapid Electroplating Method.

A simple electrochemical method is developed in this study to weld the contact points in silver nanowire (AgNW) thin films. The AgNW thin film is first fabricated by spray coating and then submerged in a silver plating solution. By applying electrical potential over the AgNW thin films, silver ions in the plating solution are reduced into silver nanoparticles preferentially over nanowires and solder the nanomesh structures. Due to the large current density between silver nanowires, nanoparticles generated in the electroplating reaction mainly appeared at the junction. The electroplated AgNW network not only shows better conductivity with a negligible loss of transmittance, but also exhibit much better mechanical strength in the bending test.

Stability Analysis of Printed Liquid Elbows.

In this study, a theoretical model was developed to analyze the stability of liquid elbow patterns and validated by experiments. An exemplar system of ethylene glycol continuously deposited on polyethylene terephthalate (PET) was used to study the effects of printing parameters on bulge formation near the elbow corners. In the elbow region, because of the capillary pressure differences, liquids flowed into the concave elbow corner and formed bulges easily after being printed. However, the bulge formation disappeared when the elbow angle is >90°. A simple model based on surface energy analysis was proposed to explain the bulging phenomenon and can successfully predict bulge sizes at steady state. A stability diagram was also calculated to map out the stable regimes. With the guidance of the stability diagram, stable elbow lines without any bulges can be printed with various angles by controlling the thickness of liquids. In summary, this stabilization strategy in this study is effective to maintain the fidelity of printed liquid patterns and provides useful guidelines for printed electronic applications.

Accelerated Sedimentation Velocity Assessment for Nanowires Stabilized in a Non-Newtonian Fluid.

In this work, the long-term stability of titanium oxide nanowire suspensions was accessed by an accelerated sedimentation with centrifugal forces. Titanium oxide (TiO2) nanoparticle (NP) and nanowire (NW) dispersions were prepared, and their sizes were carefully characterized. To replace the time-consuming visual observation, sedimentation velocities of the TiO2 NP and NW suspensions were measured using an analytical centrifuge. For an aqueous TiO2 NP suspension, the measured sedimentation velocities were linearly dependent on the relative centrifugal forces (RCF), as predicted by the classical Stokes law. A similar linear relationship was also found in the case of TiO2 NW aqueous suspensions. However, NWs preferred to settle parallel to the centrifugal direction under high RCF because of the lower flow resistance along the long axis. Thus, the extrapolated sedimentation velocity under regular gravity can be overestimated. Finally, a stable TiO2 NW suspension was formulated with a shear thinning fluid and showed great stability for weeks using visual observation. A theoretical analysis was deduced with rheological shear-thinning parameters to describe the nonlinear power-law dependence between the measured sedimentation velocities and RCF. The good agreement between the theoretical predictions and measurements suggested that the sedimentation velocity can be properly extrapolated to regular gravity. In summary, this accelerated assessment on a theoretical basis can yield quantitative information about long-term stability within a short time (a few hours) and can be further extended to other suspension systems.

Metal-Organic Framework Colloids: Disassembly and Deaggregation.

We demonstrate a high-resolution method as an efficient tool to in situ characterize partially reversible assembly and aggregation of metal-organic framework (MOF) colloids. Based on the gas-phase electrophoresis, the primary size and the degree of aggregation of the MOF-525 crystals are tunable by pH adjustment and mobility selection. These findings allow for the further size control of MOF colloids and prove the capability of semiquantitative analysis for the MOF-based platforms in a variety of aqueous formulations (e.g., biomedical applications).

Highly stretchable and conductive silver nanowire thin films formed by soldering nanomesh junctions.

Silver nanowires (AgNWs) have been widely used for stretchable and foldable conductors due to their percolating network nanostructure. To enhance the mechanical strength of AgNW thin films under extreme stretching conditions, in this study, we utilize a simple chemical reaction to join AgNW network connections. Upon applying a reactive ink over AgNW thin films, silver nanoparticles are preferentially generated over the nanowire junctions and solder the nanomesh structures. The soldered nanostructure reinforces the conducting network and exhibits no obvious change in electrical conductivity in the stretching or rolling process with elongation strains up to 120%. Several examples are also demonstrated to show potential applications of this material in stretchable electronic devices.

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.

Photocurable Foam for Three-Dimensional-Printed Porous Structures.

In this research, a foam three-dimensional (3D) printing method using digital light processing (DLP) technology was developed to fabricate 3D-printed porous structures. To address the challenges in preparing DLP precursor foam fluid, we designed a specialized foaming device. This device enables the precursor solution to be blended with air, resulting in a stable foam precursor with an adjustable air/liquid fraction and suitable fluidity, crucially enhancing the gas-liquid contact time for the printing process. By manipulation of fluid flow rates, cycle counts, and gas/liquid ratios, one can easily prepare uniform foams with precise control over the pore size and porosity. To avoid significant volume reduction during ultraviolet (UV) curing, nanoparticle fillers were introduced into the network to prevent collapse of the foam structure. Furthermore, the inclusion of an UV absorber enhanced the quality of the printing process by addressing the limitations associated with particle scattering and reflection. The DLP process can readily fabricate intricate structures, featuring a planar resolution below 30 µm and a printing accuracy of less than 1%. Several examples were also demonstrated to highlight the advantages of this technology and its ability to directly print custom foam structures, thereby saving time and material resources.

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.

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.

Drastic changes in interfacial hydrodynamics due to wall slippage: slip-intensified film thinning, drop spreading, and capillary instability.

We report that wall slippage can drastically change both steady and dynamic flow characteristics for a wide class of free-surface thin film flows. This is demonstrated by (i) the breakdown of the 2/3 law and its replacement by a new quadratic law for the deposited film thickness in the Landau-Levich-Bretherton coating, (ii) the departure from de Gennes-Tanner's cubic law for dynamic contact angles in drop spreading, consequently resulting in much faster spreading than the classical Tanner law, and (iii) the exaggerated capillary instability of an annular film where a fractional amount of wall slip can lead to much more rapid draining and hence make the film more vulnerable to rupture. In (ii), the molecular precursor film is shown to have a length varying like the -1/2 power of the spreading speed, producing an anomalous 1/3 diffusion law governing its spreading dynamics. A variety of existing experimental findings can be well captured by the new scaling laws we derive. All these features are accompanied with no-slip-to-slip transitions, offering alternative means for probing slip boundaries.

Preserving precision of inkjet-printed features with solvents of different volatilities.

For printed micropatterns on plastic substrates, the decreasing volume because of solvent evaporation frequently leads to contact line receding and changes the original printed pattern. To prevent printing quality deterioration caused by contact line motions, an ink formulation method was developed. A nearly non-volatile solvent [polyethylene glycol (PEG)] with a low receding angle on polyethylene terephthalate (PET) sheets was added in water to hold the contact line. To understand the dewetting phenomena of inks, the geometrical evolution of circular liquid films under evaporation was recorded and analyzed. The results showed that the contact line receded as water evaporated for inks with low PEG concentrations but remained pinned at a moderate PEG concentration (~10 wt %). A simple model was proposed to explain the dewetting phenomena and can successfully predict the critical PEG concentration, beyond which the contact lines will be unconditionally pinned. The optimized water/PEG solvent can then be used to prepare dye- or particle-based inks, which preserved accurate features after solvent evaporation.

Contact angle hysteresis on textured surfaces with nanowire clusters.

Nanowire arrays with various agglomeration patterns were synthesized by adjusting the solvent evaporation rates. Nanowires with 200 nm diameter and 2-25 microm in length were fabricated from an anodic aluminum oxide (AAO) porous template. Various drying treatments were applied to develop nanostructured surfaces with topological differences. Due to surface tension forces, copper nanowires after thermal and evaporative drying treatments agglomerated into clusters, while supercritical drying technique provided excellent bundled-free and vertically-standing nanowire arrays. Although all dried surfaces exhibited hydrophobic nature, the contact angle hysteresis, or the difference between advancing and receding angles, was found to be larger on those surfaces with bundled nanowire clusters. To explain the difference, the wetted solid fraction on each surface was calculated using the Cassie-Baxter model to show that the hysteresis was contributed by liquid/solid contact area on the textured surfaces.

Self-assembled mesoporous silica nanoparticles in controlled patterns produced by soft-lithography and ink-jet printing.

This study demonstrate assembly of mesoporous silica nanoparticles (MSNs) into various patterns by soft-lithography and ink-jet printing techniques. A clear suspension containing MSNs with a particle size around 58 nm is firstly synthesized. Then, soft-lithographic techniques (i.e., MIMIC, impression with PDMS) and an ink-jet printing technique are applied to create various patterns assembled by MSNs. The MIMIC method results in a high density of MSNs, but is limited to linear patterns due to the capillary principle. The impression method led to MSN colloids in various patterns, but the MSNs assembled in low density due to the lack of the colloidal supplements. The ink-jet technique can create various patterns more conveniently, and the final patterns are generated after a de-wetting process. During the de-wetting process, the MSN concentrations and the jetted times are related only to the final number of particles dispersed in patterns. Comparison of different patterning techniques will be helpful towards creation of patterned assembly with MSNs.