Stretchable Piezoresistive Pressure Sensor Array with Sophisticated Sensitivity, Strain-Insensitivity, and Reproducibility.

This study delves into the development of a novel 10 by 10 sensor array featuring 100 pressure sensor pixels, achieving remarkable sensitivity up to 888.79 kPa-1, through the innovative design of sensor structure. The critical challenge of strain sensitivity inherent is addressed in stretchable piezoresistive pressure sensors, a domain that has seen significant interest due to their potential for practical applications. This approach involves synthesizing and electrospinning polybutadiene-urethane (PBU), a reversible cross-linking polymer, subsequently coated with MXene nanosheets to create a conductive fabric. This fabrication technique strategically enhances sensor sensitivity by minimizing initial current values and incorporating semi-cylindrical electrodes with Ag nanowires (AgNWs) selectively coated for optimal conductivity. The application of a pre-strain method to electrode construction ensures strain immunity, preserving the sensor's electrical properties under expansion. The sensor array demonstrated remarkable sensitivity by consistently detecting even subtle airflow from an air gun in a wind sensing test, while a novel deep learning methodology significantly enhanced the long-term sensing accuracy of polymer-based stretchable mechanical sensors, marking a major advancement in sensor technology. This research presents a significant step forward in enhancing the reliability and performance of stretchable piezoresistive pressure sensors, offering a comprehensive solution to their current limitations.

Full integration of highly stretchable inorganic transistors and circuits within molecular-tailored elastic substrates on a large scale.

The emergence of high-form-factor electronics has led to a demand for high-density integration of inorganic thin-film devices and circuits with full stretchability. However, the intrinsic stiffness and brittleness of inorganic materials have impeded their utilization in free-form electronics. Here, we demonstrate highly integrated strain-insensitive stretchable metal-oxide transistors and circuitry (442 transistors/cm2) via a photolithography-based bottom-up approach, where transistors with fluidic liquid metal interconnection are embedded in large-area molecular-tailored heterogeneous elastic substrates (5 × 5 cm2). Amorphous indium-gallium-zinc-oxide transistor arrays (7 × 7), various logic gates, and ring-oscillator circuits exhibited strain-resilient properties with performance variation less than 20% when stretched up to 50% and 30% strain (10,000 cycles) for unit transistor and circuits, respectively. The transistors operate with an average mobility of 12.7 ( ± 1.7) cm2 V-1s-1, on/off current ratio of > 107, and the inverter, NAND, NOR circuits operate quite logically. Moreover, a ring oscillator comprising 14 cross-wired transistors validated the cascading of the multiple stages and device uniformity, indicating an oscillation frequency of ~70 kHz.

Water-Triggered Self-Healing of Ti3C2Tx MXene Standalone Electrodes: Systematic Examination of Factors Affecting the Healing Process.

MXenes, with their remarkable attributes, stand at the forefront of diverse applications. However, the challenge remains in sustaining their performance, especially concerning Ti3C2Tx MXene electrodes. Current self-healing techniques, although promising, often rely heavily on adjacent organic materials. This study illuminates a pioneering water-initiated self-healing mechanism tailored specifically for standalone MXene electrodes. Here, both water and select organic solvents seamlessly mend impaired regions. Comprehensive evaluations around solvent types, thermal conditions, and substrate nuances underline water's unmatched healing efficacy, attributed to its innate ability to forge enduring hydrogen bonds with MXenes. Optimal healing environments range from ambient conditions to a modest 50 °C. Notably, on substrates rich in hydroxyl groups, the healing efficiency remains consistently high. The proposed healing mechanism encompasses hydrogen bonding formation, capillary action-induced expansion of interlayer spacing, solvent lubrication, Gibbs free energy minimizing MXene nanosheet rearrangement, and solvent evaporation-triggered MXene layer recombination. MXenes' resilience is further showcased by their electrical revival from profound damages, culminating in the crafting of Joule-heated circuits and heaters.

Convolution Neural Networks for Motion Detection with Electrospun Reversibly-Cross-linkable Polymers and Encapsulated Ag Nanowires.

This paper presents the design, fabrication, and implementation of a novel composite film, a polybutadiene-based urethane (PBU)/AgNW/PBU sensor (PAPS), demonstrating remarkable mechanical stability and precision in motion detection. The sensor capitalizes on the integration of Ag nanowire (AgNW) electrodes into a neutral plane, embedded within a reversibly cross-linkable PBU polymer. The meticulous arrangement confers pore-free and interfaceless sensor formation, resulting in an enhanced mechanical robustness, reproducibility, and long-term reliability. The PBU polymer is subjected to an electrospinning process, followed by sequential Diels-Alder (DA) and retro-DA reactions to produce a planarized encapsulation layer. This pioneering technology, based on electrospinning, allows for more flawless engineering of the neutral plane as compared to conventional film lamination or layer-by-layer spin-coating processes. This encapsulation, matching the thickness of the preformed PBU film, effectively houses the AgNW electrodes. The PAPS outperforms conventional AgNW/PBU sensors (APS) in terms of mechanical stability and bending insensitivity. When affixed to various body parts, the PAPS generates distinctive signal curves, reflecting the specific body part and degree of motion involved. The PAPS sensor's utility is further magnified by the application of machine learning and deep learning algorithms for signal interpretation. K-means clustering algorithm authenticated the superior reproducibility and consistency of the signals derived from the PAPS over the APS. Deep learning algorithms, including a singular 1D convolutional neural network (1D CNN), long short-term memory (LSTM) network, and dual-layered combinations of 1D CNN + LSTM and LSTM + 1D CNN, were deployed for signal classification. The singular 1D CNN model displayed a classification accuracy exceeding 98%. The PAPS sensor signifies a pivotal development in the field of intelligent motion sensors.

Measurement of proximal contact of single crowns to assess interproximal relief: A pilot study.

Background: It is common for dental technicians to adjust the proximal surface of adjacent teeth on casts when fabricating single crowns. However, whether the accuracy of the proximal contact is affected if this step is eliminated is unclear. Objective: To evaluate the accuracy of the proximal contact of single crowns for mandibular first molars fabricated from four different restorative materials, without adjustment of the proximal surface of the adjacent teeth by the laboratory/dental technician. Methods: This study was in vitro; all the clinical procedures were conducted on a dentoform. The mandibular first molar tooth on the dentoform was prepared using diamond burs and a high speed handpiece. Twenty single crowns were fabricated, five for each group (monolithic zirconia, lithium disilicate, metal ceramic, and cast gold). No proximal surface adjacent to the definitive crowns was adjusted for tight contact in the dental laboratory. Both the qualitative analyses, using dental floss and shimstock, and the quantitative analyses, using a stereo microscope, were performed to evaluate the accuracy of the proximal contact of the restoration with the adjacent teeth. In the quantitative analysis, one-way analysis of variance was used to compare mean values at a significance level of 0.05. Results: In quantitative analysis, the differences between the proximal contact tightness of the four groups was not statistically significant (P = 0.802 for mesial contacts, P = 0.354 for distal contacts). In qualitative analysis, in most crowns, dental floss passed through the contact with tight resistance and only one film of shimstock could be inserted between the adjacent teeth and the restoration. However, one specimen from the cast gold crown had open contact. Conclusions: Even without proximal surface adjustment of the adjacent teeth during the crown fabrication process, adequate proximal contact tightness between the restoration and adjacent teeth could be achieved.

Static electricity-based motion artifact-free electrocardiography with novel Ti3C2Tx MXene/Ag nanowire/polymer hybrid dry electrodes.

With wearable devices featuring electrocardiogram (ECG) capabilities increasingly common, demand for accurate, simple ECG measurements has escalated. Although single-lead ECGs, which capture real-time heart rate and rhythm, are typically used in such devices, they encounter challenges related to the device-skin contact state, complicating serious heart disease prediction. While 12-lead ECGs provide superior measurements, they require wet electrodes, which are unsuitable for long-term use due to skin irritation and signal degradation over time. Dry electrodes have been explored as a potential resolution to this issue, yet they necessitate a substantial conductive surface area coupled with a stable contact to achieve low contact impedance with the skin. For the first time, we hereby propose a novel approach that simultaneously addresses the exigencies for substantial conductive surface coverage and remarkable contact stability, facilitating an ECG free from motion artifacts. The electrodes we propose are constituted by silver nanowires (AgNWs) entrenched beneath the surface of a polymer film, thereby displaying superior mechanical flexibility and lateral electrical conductivity. To counterbalance the restricted surface coverage of the embedded AgNW electrode, we integrated Ti3C2-based MXene nanosheets on the surface, thereby significantly enhancing the conductive coverage of the electrode surface. The electrostatic interaction between the functional groups on the MXene nanosheets' surface and the positively charged human skin facilitates spontaneous contact, yielding stable contact and diminished vulnerability to motion artifacts. This novel electrode design holds considerable potential for the long-term monitoring of cardiac health, offering signal quality superior to that of existing wet and dry electrodes.

Self-Repairing and Energy-Harvesting Triboelectric Sensor for Tracking Limb Motion and Identifying Breathing Patterns.

The increasing prevalence of health problems stemming from sedentary lifestyles and evolving workplace cultures has placed a substantial burden on healthcare systems. Consequently, remote health wearable monitoring systems have emerged as essential tools to track individuals' health and well-being. Self-powered triboelectric nanogenerators (TENGs) have exhibited significant potential for use as emerging detection devices capable of recognizing body movements and monitoring breathing patterns. However, several challenges remain to be addressed in order to fulfill the requirements for self-healing ability, air permeability, energy harvesting, and suitable sensing materials. These materials must possess high flexibility, be lightweight, and have excellent triboelectric charging effects in both electropositive and electronegative layers. In this work, we investigated self-healable electrospun polybutadiene-based urethane (PBU) as a positive triboelectric layer and titanium carbide (Ti3C2Tx) MXene as a negative triboelectric layer for the fabrication of an energy-harvesting TENG device. PBU consists of maleimide and furfuryl components as well as hydrogen bonds that trigger the Diels-Alder reaction, contributing to its self-healing properties. Moreover, this urethane incorporates a multitude of carbonyl and amine groups, which create dipole moments in both the stiff and the flexible segments of the polymer. This characteristic positively influences the triboelectric qualities of PBU by facilitating electron transfer between contacting materials, ultimately resulting in high output performance. We employed this device for sensing applications to monitor human motion and breathing pattern recognition. The soft and fibrous-structured TENG generates a high and stable open-circuit voltage of up to 30 V and a short-circuit current of 4 µA at an operation frequency of 4.0 Hz, demonstrating remarkable cyclic stability. A significant feature of our TENG is its self-healing ability, which allows for the restoration of its functionality and performance after sustaining damage. This characteristic has been achieved through the utilization of the self-healable PBU fibers, which can be repaired via a simple vapor solvent method. This innovative approach enables the TENG device to maintain optimal performance and continue functioning effectively even after multiple uses. After integration with a rectifier, the TENG can charge various capacitors and power 120 LEDs. Moreover, we employed the TENG as a self-powered active motion sensor, attaching it to the human body to monitor various body movements for energy-harvesting and sensing purposes. Additionally, the device demonstrates the capability to recognize breathing patterns in real time, offering valuable insights into an individual's respiratory health.

Electronic textiles: New age of wearable technology for healthcare and fitness solutions.

Sedentary lifestyles and evolving work environments have created challenges for global health and cause huge burdens on healthcare and fitness systems. Physical immobility and functional losses due to aging are two main reasons for noncommunicable disease mortality. Smart electronic textiles (e-textiles) have attracted considerable attention because of their potential uses in health monitoring, rehabilitation, and training assessment applications. Interactive textiles integrated with electronic devices and algorithms can be used to gather, process, and digitize data on human body motion in real time for purposes such as electrotherapy, improving blood circulation, and promoting wound healing. This review summarizes research advances on e-textiles designed for wearable healthcare and fitness systems. The significance of e-textiles, key applications, and future demand expectations are addressed in this review. Various health conditions and fitness problems and possible solutions involving the use of multifunctional interactive garments are discussed. A brief discussion of essential materials and basic procedures used to fabricate wearable e-textiles are included. Finally, the current challenges, possible solutions, opportunities, and future perspectives in the area of smart textiles are discussed.

Role of Oxygen in the Ti3AlC2 MAX Phase in the Oxide Formation and Conductivity of Ti3C2-Based MXene Nanosheets.

Ti3C2Tx MXene, a two-dimensional transition metal carbide, has attracted substantial interest due to its unique physical properties and a wide range of potential applications. Although the properties of devices using MXene have been substantially enhanced in recent years, it is not fully understood how the oxygen concentration in Ti3AlC2 MAX affects oxide formation in Ti3C2-based MXene nanosheets and their fundamental properties. To this end, we compared two types of MAX phases: MAX with low oxygen content (LO-MAX) and MAX synthesized by a conventional process. Since the conventional MAX synthesis employs metal (Ti) as a primary material, it is referred to as metal-based MAX (MB-MAX) from here. The oxygen content of the LO-MAX was only 0.56 wt %, which was about 20% compared to that of MAX synthesized using conventional methods. We compared the properties of MXene nanosheets prepared from the LO-MAX with MXene nanosheets obtained from the MB-MAX. Microscopic and chemical analyses revealed smooth and wrinkle-free morphology and small amounts of oxygen in MXene nanosheets prepared from LO-MAX (LO-MXene). The LO-MXene nanosheet film exhibited an exceptionally high conductivity of 10,540 S/cm and an ultralow surface roughness of 1.7 nm, which originated from inhibited surface oxide formation. Moreover, the inhibition of oxide formation strengthened the function of -O or -OH groups on the surface of MXene, thereby facilitating strong hydrogen bonding to the polymer with hydroxyl groups. To clearly reveal these properties, we prepared a pressure sensor by coating these MXene nanosheets on nylon/polyester fibers. The fabricated sensor exhibited a high sensitivity of up to 85.6/kPa and excellent stretch stability and reliability. These results clearly revealed that lowering the oxygen content in MAX can make a decisive contribution to improving the fundamental properties of MXene nanosheets prepared therefrom.

Self-powered image array composed of touch-free sensors fabricated with semiconductor nanowires.

We successfully develop a self-powered image array (IA) composed of 16 touch-free sensors (TFSs) fabricated with semiconductor InN nanowires (NWs) as a response medium. Without using a power supply, the InN-NW TFS can detect the position of a human hand 30 cm away from the device surface. It also distinguishes different materials such as polyimide, Al foil, printing paper, latex, and polyvinyl chloride in non-contact mode at a distance of 1 cm. The self-powered TFS-IA clearly distinguishes square-shaped transparent polydimethylsiloxane film attached to the back of a human hand positioned 5 cm from the device, indicating the possibility for detecting changes in the surface texture of human skin, such as skin burns or skin cancer. The performance of the self-powered TFS and TFS-IA is attributed to high electrostatic induction of InN NWs by external triboelectricity resulting from the simple movement of the target object, which differs markedly from conventional sensors designed to detect variations in the temperature or light essentially using a power supply.

Stretchable Inorganic GaN-Nanowire Photosensor with High Photocurrent and Photoresponsivity.

To effectively implement wearable systems, their constituent components should be made stretchable. We successfully fabricated highly efficient stretchable photosensors made of inorganic GaN nanowires (NWs) as light-absorbing media and graphene as a carrier channel on polyurethane substrates using the pre-strain method. When a GaN-NW photosensor was stretched at a strain level of 50%, the photocurrent was measured to be 0.91 mA, corresponding to 87.5% of that (1.04 mA) obtained in the released state, and the photoresponsivity was calculated to be 11.38 A/W. These photosensors showed photocurrent and photoresponsivity levels much higher than those previously reported for any stretchable semiconductor-containing photosensor. To explain the superior performances of the stretchable GaN-NW photosensor, it was approximated as an equivalent circuit with resistances and capacitances, and in this way, we analyzed the behavior of the photogenerated carriers, particularly at the NW-graphene interface. In addition, the buckling phenomenon typically observed in organic-based stretchable devices fabricated using the pre-strain method was not observed in our photosensors. After a 1000-cycle stretching test with a strain level of 50%, the photocurrent and photoresponsivity of the GaN-NW photosensor were measured to be 0.96 mA and 11.96 A/W, respectively, comparable to those measured before the stretching test. To evaluate the potential of our stretchable devices in practical applications, the GaN-NW photosensors were attached to the proximal interphalangeal joint of the index finger and to the back of the wrist. Photocurrents of these photosensors were monitored during movements made about these joints.

One-Way Continuous Deposition of Monolayer MXene Nanosheets for the Formation of Two Confronting Transparent Electrodes in Flexible Capacitive Photodetector.

MXenes based on titanium carbide are promising next-generation transparent electrode materials due to their high metallic conductivity, optical transparency, mechanical flexibility, and abundant hydrophilic surface functionality. MXene electrodes offer a much wider conductive surface coverage than metal nanowires, thereby gaining popularity as flexible electrode materials in supercapacitors and energy devices. However, given that monolayer MXene nanosheets are only a few nanometers thick, meticulous surface treatments and deposition technologies are required for a practical implementation of these transparent electrodes. Unfortunately, a capacitor produced by forming high-quality transparent MXene electrodes on both sides of a film has not yet been reported. We report the successful development of a one-way continuous deposition technology to form high-quality MXene nanosheet-based transparent electrodes on both surfaces of a polymer film without large physical stresses on the MXene nanosheets. One transparent electrode was formed by transferring MXene nanosheets predeposited on a temporary glass substrate to the film surface, while the other was directly deposited on the exposed film surface. The Ti3AlC2 precursor (MAX) was synthesized via a spark plasma sintering crystallization, and the MXene nanosheets were prepared via a subsequent Al-selective etching and delamination. We used this material to implement a capacitive photodetector consisting of two layers of opposing transparent electrodes. The flexible photodetector was based on poly(vinyl butyral) (PVB), which was solidly bonded with MXene nanosheets to serve as a free-standing binder for the Cu-doped ZnS semiconductor particles. The fabricated device exhibited excellent mechanical stability due to the high affinity between the MXene nanosheets and PVB. Furthermore, the device exhibited an initial capacitance of 2 nF, photosensitivity of 12.5 µF/W, and rise and decay times of 0.031 and 0.751 s, respectively. All these parameters were 1 to 2 orders of magnitude higher or faster than reported capacitive photodetectors. Overall, the proposed approach resolves the core issues associated with existing metal nanowire-based electrodes, and it is a breakthrough in the development of next-generation flexible devices comprising two layers of confronting transparent electrodes.

Solution process manufacture of a simple, multifunctional flexible sensor based on capacitance measurement.

Conventional sensors are rigid, involve complex processes and structures, and one sensor can detect only one type of stimulus. The manufacturing costs of such devices are high owing to the use of vacuum processes for the formation of thin films and electrodes and the complicated fabrication processes required to construct multiple layers. In addition, the multiple-layer design increases the risk of peeling due to mechanical movement. In this study, to solve the aforementioned problems, a simple two-layer multi-sensor has been fabricated using a non-vacuum solution process. The sensor consists of a light absorption layer comprising polyvinyl butyral and semiconductor particles and a top layer comprising two spiral-shaped Ag nanowire electrodes. The sensor experiences minimal damage by external adhesives and has a light-sensitive optical response at 420 nm and at 1.2 mW cm-2. Herein, the capacitance of the sensor applied to the two-electrode structure was determined, along with the light sensitivity and change in noise with frequency. We believe that the proposed multi-sensor can be applied in a wide range of fields because it can act as a touch sensor and light sensor.

Pressure-Sensitive Adhesive with Controllable Adhesion for Fabrication of Ultrathin Soft Devices.

As the interest in foldable smartphones recently launched onto the market shifts toward the next generation of flexible electronics, the development of ultrathin devices is gaining considerable attention. The strain formed on the surfaces of film-based devices approximates the film thickness divided by twice the radius of curvature; therefore, the use of an ultrathin substrate is the key for the development of next generation foldable devices. However, the stiffness of ultrathin films is extremely low; thus, it cannot be easily used directly as a substrate for device fabrication. Therefore, these films generally undergo device manufacturing processes while being attached to a rigid substrate such as glass and are peeled from the rigid substrate after the process is finished. Thus, the initial adhesion of the adhesive used to fix the film to the temporary substrate should be strong, and after the process is completed, the adhesion must be lessened to enable soft peeling. In this study, we succeeded in developing a novel pressure-sensitive adhesive (PSA) whose adhesive strength can be severely reduced by water treatment. Accordingly, considering that amphiphilic oligomers promote water absorption through hydrogen bonding to water, amphiphilic oligomers were mixed with an acrylic polymer to prepare the water-responsive PSA (wr-PSA). The adhesion strength of the wr-PSA in the early stage, which reached 382(±22) N/m, dramatically dropped to 9(±2) N/m after a water immersion test. Using the wr-PSA, a 1.4 µm-thick polyethylene terephthalate film coated with Ag nanowires was softly peeled off from the glass after being immersed in warm water. In addition, the adhesion reduced by the immersion in water was recovered again when the water absorbed by the adhesive was dried. This implies that the developed adhesive can be reusable.

Ultrafast Photoinduced Interconnection of Metal-Polymer Composites for Fabrication of Transparent and Stretchable Electronic Skins.

The high interest sparked by the foldable smartphones recently released on the market is gradually shifting to the next generation of flexible electronic devices, such as electronic skins in the form of stretchable thin films. To develop such devices, good mechanical flexibility of all components (including the substrate, electrode, and encapsulant) is critical. Various technologies have been developed to enhance the flexibility of these components; however, progress in developing interconnection methods for flexible and stretchable devices has been limited. Here, we developed an ultrafast photoinduced interconnection method that does not require any adhesive or surface treatment. This method is based on heating metal nanostructures using intense pulsed light (IPL) and the reversible cross-linking of polymers. First, we synthesized a stretchable, transparent, and free-standing polymer substrate that can be reversibly cross-linked, and then Ag nanowire (AgNW) networks were formed on its surface. This electrode was irradiated with IPL, which locally heated the AgNWs, followed by decomposition of the polymer via the retro-Diels-Alder reaction and recross-linking. Independently fabricated AgNW/polymer films were layered and irradiated three times with IPL to form a bonded sample with excellent joint quality and no increase in electrical resistance compared to a single electrode. Furthermore, the interconnected electrodes were stretchable and optically transparent. Even when more than 200% strain was applied in a peel test, no breakage at the joint was observed. This allowed us to successfully produce a stretchable, transparent, and bending-insensitive pressure sensor for various applications such as motion detectors or pressure sensor arrays.

A Behavior-Learned Cross-Reactive Sensor Matrix for Intelligent Skin Perception.

Mimicking human skin sensation such as spontaneous multimodal perception and identification/discrimination of intermixed stimuli is severely hindered by the difficulty of efficient integration of complex cutaneous receptor-emulating circuitry and the lack of an appropriate protocol to discern the intermixed signals. Here, a highly stretchable cross-reactive sensor matrix is demonstrated, which can detect, classify, and discriminate various intermixed tactile and thermal stimuli using a machine-learning approach. Particularly, the multimodal perception ability is achieved by utilizing a learning algorithm based on the bag-of-words (BoW) model, where, by learning and recognizing the stimulus-dependent 2D output image patterns, the discrimination of each stimulus in various multimodal stimuli environments is possible. In addition, the single sensor device integrated in the cross-reactive sensor matrix exhibits multimodal detection of strain, flexion, pressure, and temperature. It is hoped that his proof-of-concept device with machine-learning-based approach will provide a versatile route to simplify the electronic skin systems with reduced architecture complexity and adaptability to various environments beyond the limitation of conventional "lock and key" approaches.

Self-Integratable, Healable, and Stretchable Electroluminescent Device Fabricated via Dynamic Urea Bonds Equipped in Polyurethane.

Reversible bonding between polymer chains has been used primarily to induce self-healing of damaged polymers. Inspired by the dynamic nature of such bonding, we have developed a polyurethane equipped with dynamic urea bonds (PEDUB) that has high strength sufficient to make it be freestanding and have a healing capability and self-bonding property. This allowed subsequent heterogeneous multicomponent device integration of electrodes/substrate and light-emitting pixels into a light-emitting device. We first used the PEDUB to individually fabricate a highly stretchable electrode containing Ag nanowires and stretchable composites with ZnS-based particles. They were successfully assembled into a stretchable, waterproof electroluminescent (EL) device even under mild conditions (60 °C for 10 min) owing to the reversible exchange of urea bonds and low glass transition temperature of PEDUB. The assembled device with an AC-driven EL architecture retained excellent EL characteristics even after stretching, submersion in water, and cutting owing to the robust solid-state bonding interfaces induced by the dynamic urea bonds. Consequently, various shapes of the illuminating elastomer and an illuminated picture were realized for the first time using the mosaic-like assembly method. This first demonstration of multicomponent assembly paves the way for future stretchable multifunctional devices.

Fabrication of a Bending-Insensitive In-Plane Strain Sensor from a Reversible Cross-Linker-Functionalized Silicone Polymer.

A reversibly cross-linkable and transparent polymer featuring stretchability and thermal healability is prepared by introducing Diels-Alder (DA)-reactive moieties into polydimethylsiloxane (PDMS), namely, a healable PDMS (h-PDMS). Inspired by the fact that retro-DA reactions occur even at low temperatures (albeit at a low rate), we maximize the effectiveness of small reactant products, demonstrating that self-healing and self-integration realized by 1-3 min exposure of cured h-PDMS to methyl ethyl ketone (MEK) vapor is more efficient than that achieved by direct sample heating at high temperatures. This technology is first used to uniformly transfer Ag nanowires (Ag NWs) formed on a temporary substrate to the h-PDMS surface, and further MEK vapor treatment allows the transferred NWs to be impregnated below the h-PDMS surface to afford an in-plane strain sensor. Most importantly, the developed method is used to perfectly integrate two identical Ag NW/h-PDMS films and thus place NWs on a neutral plane. Consequently, because of the unique structure in which a percolated network of AgNWs is formed on the interface where the two identical h-PDMS films are chemically integrated, the fabricated sensor is transparent, self-healable, stretchable, and insensitive to bending but sensitively responds to in-plane strain induced by lateral deformation.

Net Energy Net Energy Net EnergyNet EnerNet Energy of high-protein sunflower meal fed to growing pigs and effect of dietary phosphorus on measured values of NE.

An experiment was carried out to determine energy values of high-protein sunflower meal (HP-SFM) and to compare the energy values of HP-SFM determined using either a phosphorus (P)-deficient basal diet or a P-adequate basal diet. Twenty-four growing barrows were randomly assigned to 1 of 4 dietary treatments with 6 replicates per treatment. Four experimental diets including 2 basal diets containing 2 levels of standardized total tract digestible P (i.e., P-deficient and P-adequate) and the other 2 diets containing 30% HP-SFM with each basal diet (i.e., HP-SFM 1 diet and HP-SFM 2 diet) were formulated to determine the energy values of HP-SFM and to compare energy values of HP-SFM determined by the difference method using 2 basal diets. Pigs were fed diets for 15 d including 10 d for adaptation and 5 d for total collections. Pigs were then moved to indirect calorimetry chambers to determine total heat production (THP) and fasting heat production (FHP). A reduced (P < 0.01) amount of nitrogen was retained in pigs fed the P-deficient basal diet compared with those fed the other diets. The THP of pigs fed the HP-SFM 1 and 2 diets was greater (P < 0.01) than those fed the P-deficient basal diet with the intermediate value for pigs fed the P-adequate basal diet. The retained energy (RE) as protein of pigs fed the P-deficient basal diet was less (P < 0.01) but RE as lipid was greater (P < 0.01) than those fed the P-adequate basal, or HP-SFM 1 and 2 diets. However, there was no difference in FHP of pigs among the dietary treatments. The NE of HP-SFM determined using the P-deficient basal diet was 2,062 kcal/kg, as-fed basis, whereas the value determined using the P-adequate basal diet was 2,151 kcal/kg. Although no differences were observed in energy values, the amount of P in basal diet might affect energy balance by modifying N utilization, thus, a diet containing adequate amount of P is a more suitable basal diet when the difference method is used for calculation of NE in a feed ingredient.