Copper Ion Doped Mullite Composite in Poly (vinylidene Fluoride) Matrix: Effect on Microstructure, Phase Behavior and Electrical Properties

Highly crystallized copper ion doped mullite composites have been synthesized at 1100°C and 1400°C via sol-gel technique with five different strengths of copper ion and was incorporated in poly-vinylidene fluoride (PVDF) to make doped mullite composite/polymer films. We have studied the effects of this dopant on microstructure, phase transformation, and electrical properties of the polymer films over a wide range of frequency from 1.0 KHz to 2.0 MHz. Characterizations were done by various analytical tools at room temperature. Prominent mullite phases were observed from XRD, FTIR spectroscopy and FESEM characterization of composite polymer. The concentration of the dopant and the sintering temperature were found to be the two basic factors which affect the phase transition of the polymer. The composite film showed maximum dielectric constant of 19.96 at 1 KHz for 1.2M concentration of copper ion doped mullite sintered at 1400°C, compared to 3.09 for the pure polymer. Furthermore, both dielectric constant and electrical conductivity of the composite were found to be highly frequency and temperature dependent. After doping, the A.C. conductivity of the composite was found to increase with increasing temperature following Jonscher's power law and the electrical resistivity reduced too. Moreover, the results revealed that the phase behaviors and micro structural changes of the copper ion doped mullite composite/polymer film affected its electrical properties with possible impact on its applications

ELECTRICAL RESISTIVITY AND ACTIVATION ENERGY OF COBALT ACETATE TETRAHYDRATE DOPED MULLITE

Mullite composites have been synthesized at 400°C, 800°C, 1000°C and 1300°C via the sol-gel technique in the presence of cobalt. The electrical resistivity and activation energy of the composites have been measured and their variation with concentration of the metal ion doping has been investigated. The resistivity of doped mullite decreases rapidly from 400°C-800°C more gently from 1000°C-1300°C. The lowering of resistivity is due to the 3d orbital electrons and the concentration of cobalt ions. X-ray analysis confirms the presence of Co2+ ions in mullite, which entered the octahedral site. The Co2+ ion which substituted Al3+ ion in the octahedral site of mullite structure appeared to be efficient in reducing the resistivity. This has been confirmed due to the results of activation energy of resistivity/band gap energy, the Eg which was lowest for concentration 0.15 M. As the concentration increases, these ions lower the resistivity of mullite to a minimum

Transmissive Labyrinthine Acoustic Metamaterial‐Based Holography for Extraordinary Energy Harvesting

Conventional energy sources are continuously depleting, and the world is actively seeking new green and efficient energy solutions. Enormous amounts of acoustic energy are dissipated daily, but the low intensity and limited efficiency of current harvesting techniques are preventing its adoption as a ubiquitous method of power generation. Herein, a strategic solution to increase acoustic energy harvesting efficiency using a specially designed metamaterial is implemented. A scalable transmissive labyrinthine acoustic metamaterial (LAM) is designed, developed, and employed to maximize ultrasound (40 kHz) capture over its large surface area (>27 k mm2), which is focused onto a piezoelectric film (78.6 mm2), thus magnifying incident sound pressure by 13.6 times. Three different piezoelectric films – two commercial and one lab-made nanocomposite film are tested with LAM in the acoustic energy harvesting system. An extraordinary voltage gain of 157–173% and a maximum power gain of 272% using the LAM compared to the case without the LAM are achieved. Multipoint focusing using holographic techniques, showcasing acoustic patterning to allow on-demand simultaneous harvesting in separate locations, is demonstrated. Our versatile approach for high-intensity acoustic energy harvesting opens future opportunities to exploit sound energy as a resource to contribute toward global sustainability

In situ synthesis of environmentally benign montmorillonite supported composites of Au/Ag nanoparticles and their catalytic activity in the reduction of p-nitrophenol

In the present work, composites of montmorillonite clay supported silver and gold nanoparticles were synthesized by in situ chemical reduction method and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), UV-vis spectroscopy and Transmission Electron Microscopy (TEM). The clay-nanoparticle composites were synthesized at two different temperatures (25 degrees C and 75 degrees C) where nanoparticle size was found to depend on synthesis temperature. The distribution of the catalytic nanoparticles was uniform in the clay matrix with sizes in the range of 20-45 nm (at 25 degrees C) and 5-15 nm (at 75 degrees C), respectively. Catalytic activity of the clay-nanoparticle composites were monitored by UV-visible spectroscopy using p-nitrophenol and NaBH4 as model reactants. The best catalytic efficiency was observed in the case of silver-clay nanocomposites with a rate constant of 5.6 x 10(-3) s(-1)

Preventing stillbirth from obstructed labor: A sensorized, low-cost device to train in safer operative birth

BACKGROUND: 98% of stillbirths occur in low- and middle- income countries. Obstructed labor is a common cause for both neonatal and maternal mortality, with a lack of skilled birth attendants one of the main reasons for the reduction in operative vaginal birth, especially in low- and middle- income countries. We introduce a low cost, sensorized, wearable device for digital vaginal examination to facilitate accurate assessment of fetal position and force applied to the fetal head, to aid training in safe operative vaginal birth. METHODS: The device consists of flexible pressure/force sensors mounted onto the fingertips of a surgical glove. Phantoms of the neonatal head were developed to replicate sutures. An Obstetrician tested the device on the phantoms by performing a mock vaginal examination at full dilatation. Data was recorded and signals interpreted. Software was developed so that the glove can be used with a simple smartphone app. A patient and public involvement panel was consulted on the glove design and functionality. RESULTS: The sensors achieved a 20 Newton force range and a 0.1 Newton sensitivity, leading to 100% accuracy in detecting fetal sutures, including when different degrees of molding or caput were present. They also detected sutures and force applied with a second sterile surgical glove on top. The software developed allowed a force threshold to be set, alerting the clinician when excessive force is applied. Patient and public involvement panels welcomed the device with great enthusiasm. Feedback indicated that women would accept, and prefer, clinicians to use the device if it could improve safety and reduce the number of vaginal examinations required. CONCLUSION: Under phantom conditions to simulate the fetal head in labor, the novel sensorized glove can accurately determine fetal sutures and provide real-time force readings, to support safer clinical training and practice in operative birth. The glove is low cost (approximately 1 USD). Software is being developed so fetal position and force readings can be displayed on a mobile phone. Although substantial steps in clinical translation are required, the glove has the potential to support efforts to reduce the number of stillbirths and maternal deaths secondary to obstructed labor in low- and -middle income countries

Sol-gel synthesis of transition-metal ion conjugated alumina-rich mullite nanocomposites with potential mechanical, dielectric and photoluminescence properties

Nanocrystalline mullite have been synthesized from non-stoichiometric alkoxide precursors via sol-gel route with Co2+, Ni2+ and Cu2+ as dopant metal ions. Transition-metal aluminate spinel phases, formed from the reaction between dopant metal ions and dissolved alumina species, introduced prominent colors to the composites after sintering. Interesting colors combined with suitable densification lead these composites to have potential use as ceramic pigments. A comparative Vickers and Knoop hardness have been evaluated in terms of dislocation movement along grain boundaries with highest hardness and Young's modulus values of similar to 8.7 GPa and similar to 207 GPa for copper and cobalt incorporated mullite, respectively. Greater porosity of pure mullite results in an unconventionally high dielectric constant of similar to 91 whereas larger interfacial polarization is responsible for the varying dielectric response of transition-metal incorporated mullite composites. Formation of oxygen like defects in the composites cause prominent PL bands with highest PL intensity for dopant cobalt ions in mullite matrix

Flexible triboelectric nanogenerators using transparent copper nanowires electrodes: Energy harvesting, sensing human activities and material recognition

Triboelectric nanogenerators (TENGs) have emerged as a promising green technology to efficiently harvest otherwise wasted mechanical energy from environment and human activities. However, cost-effective and reliable TENGs require rational integration..

A Triboelectric Nanocomposite for Sterile Sensing, Energy Harvesting, and Haptic Diagnostics in Interventional Procedures from Surgical Gloves

Advanced interfacial engineering has the potential to enable the successful realization of three features that are particularly important for a variety of healthcare applications: wettability control, antimicrobial activity to reduce infection risks, and sensing of physiological parameters. Here, a sprayable multifunctional triboelectric coating is exploited as a nontoxic, ultrathin tactile sensor that can be integrated directly on the fingertips of surgical gloves. The coating is based on a polymer blend mixed with zinc oxide (ZnO) nanoparticles, which enables antifouling and antibacterial properties. Additionally, the nanocomposite is superhydrophobic (self-cleaning) and is not cytotoxic. The coating is also triboelectric and can be applied directly onto surgical gloves with printed electrodes. The sensorized gloves so obtained enable mechanical energy harvesting, force sensing, and detection of materials stiffness changes directly from fingertip, which may complement proprioceptive feedback for clinicians. Just as importantly, the sensors also work with a second glove on top offering better reassurance regarding sterility in interventional procedures. As a case study of clinical use for stiffness detection, the sensors demonstrate successful detection of pig anal sphincter injury ex vivo. This may lead to improving the accuracy of diagnosing obstetric anal sphincter injury, resulting in prompt repair, fewer complications, and improved quality of life

A stretchable, self-healing and semi-transparent nanogenerator for energy harvesting and sensing

Triboelectric nanogenerators (TENGs) with an ability to harvest mechanical energy from natural and human activities, have shown tremendous potential to realise self-powered electronic devices and sensors. However, in order for optimum utilization of biomechanical energy, TENGs need to have body or tissue mimicking properties without compromising performance. Herein, a new hydrogel based all-soft, self-healing and stretchable TENG is introduced which exhibits outstanding power generation capability surpassing existing competitors. This unique TENG is realized by using gold nanoparticles doped semi-transparent hydrogel as an electrode and Ecoflex as the triboelectric layer which integrates multifunctional properties including rapid self-healing in < 2 min, 900% stretchability, high conductivity, transparency and excellent biocompatibility with human dermal fibroblasts. The use of a gel electrode with both ionic and electronic conductivities underlines the importance of gold nanoparticles in enhancing the performance of soft TENGs. A 5 cm^{2} device exhibits a prodigious power density of 1680 mWm^{−2} with an energy conversion efficiency of ≈ 26%, which is the highest achieved so far in contemporary hydrogel based TENGs. The moldable components allow easy fabrication of devices with tunable shapes and sizes that conforms to the human body and can power multiple electrical devices directly from body movements thus opening up possibilities for next generation self-powered wearable or implanted devices

A Sensorised Surgical Glove to Analyze Forces During Neurosurgery

BACKGROUND: Measuring intraoperative forces in real time can provide feedback mechanisms to improve patient safety and surgical training. Previous force monitoring has been achieved through the development of specialized and adapted instruments or use designs that are incompatible with neurosurgical workflow. OBJECTIVE: To design a universal sensorised surgical glove to detect intraoperative forces, applicable to any surgical procedure, and any surgical instrument in either hand. METHODS: We created a sensorised surgical glove that was calibrated across 0 to 10 N. A laboratory experiment demonstrated that the sensorised glove was able to determine instrument-tissue forces. Six expert and 6 novice neurosurgeons completed a validated grape dissection task 20 times consecutively wearing the sensorised glove. The primary outcome was median and maximum force (N). RESULTS: The sensorised glove was able to determine instrument-tissue forces reliably. The average force applied by experts (2.14 N) was significantly lower than the average force exerted by novices (7.15 N) (P = .002). The maximum force applied by experts (6.32 N) was also significantly lower than the maximum force exerted by novices (9.80 N) (P = .004). The sensorised surgical glove’s introduction to operative workflow was feasible and did not impede on task performance. CONCLUSION: We demonstrate a novel and scalable technique to detect forces during neurosurgery. Force analysis can provide real-time data to optimize intraoperative tissue forces, reduce the risk of tissue injury, and provide objective metrics for training and assessment