High performance supercapacitor based on laser induced graphene for wearable devices

To ensure maximum comfort for the wearer, electronic components that include energy harvesters need to be mechanically conformable. In this context, we demonstrate a versatile, cost-effective and efficient method for fabricating graphene supercapacitor electrodes using Laser Induced Graphene (LIG). A CO2 laser beam instantly transforms the irradiated polyethersulfone polymer (PES) into a highly porous carbon structure. The LIG method was used to deposit graphene layers on graphite sheets to produce the supercapacitor electrodes. Graphene formation and morphology were examined and confirmed using several techniques including Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) spectroscopy, Raman Spectroscopy and Fourier transform infrared spectroscopy (FTIR). Moreover, the electrochemical characterization was performed in different electrolytes (NaOH and KOH). At 5 mV s-1, the LIG electrode achieved 165 mF cm-2 and 250 mF cm-2 in NaOH and KOH electrolytes, respectively. Consequently, we show that a wearable symmetric supercapacitor device with LIG electrodes achieved 98.5 mF cm-2 at 5 mV s-1 in KOH electrolyte. The device demonstrated an energy density of 11.3 μWh.cm-2 with power density of 0.33 mWcm-2 at 0.5 mA cm-2. The retention of capacitance was 75% after 2000 cycles, with outstanding performance for the comparable graphene-based electrodes. These results further validate the use of LIG for developing flexible energy harvesters for wearable applications

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

Stabilization of Carbon Nanotubes: An Infrared and Optical Spectroscopy Study on Peapods and Double-Walled Carbon Nanotubes under Pressure

The main goal of the present work is to study the stability of carbon nanotubes via the pressure-induced changes in the optical response using hydrostatic pressure transmitting medium (PTM) up to 20 GPa. For this purpose, fullerene doped SWCNTs, or what is called peapods method, was used to prepare different variety of carbon nanotubes namely: C60, C70 peapods, and double-walled carbon nanotube (DWCNTs) derived from the peapods. Additionally, iodine-filled SWCNTs (I-SWCNTs) were also prepared to extend the comparison to the effect of atoms filling on the stability of the SWCNTs and compare the results with those of the peapods and DWCNTs. The stability of the different carbon nanostructures: peapods, DWCNTs, and I-SWCNTs, against hydrostatic pressure has been mainly addressed by Raman spectroscopy, which monitors the vibrational properties of the nanotubes. Optical spectroscopy coupled with high pressure technique forms a powerful and novel tool to probe the electronic structure of carbon nanotubes. Investigations proposed that at a critical pressure, a modification of the nanotubes cross section from circular to oval, elliptical or collapse at high pressure occurs. Due to the nanotube' cross-section modification, the electronic and the optical properties of the deformed tubes are strongly affected. For example, the optical absorption spectra are altered drastically under pressure, where the main absorption bands shift to lower frequencies, broaden, lose spectral weight, and finally vanish. This behaviour was attributed to the symmetry breaking and/or σ-π hybridization. The mechanical stability of the SWCNTs by filling the tubes with molecules, atoms, or with inner tube is an important issue. High-pressure Raman measurements showed that the filling with inner tubes or Argon molecules stabilizes the outer tubes and this kind of filling considered as a case of homogenous filling. On the other hand, filling nanotubes with C70 molecules or iodine atoms, a case of inhomogeneous filling, leads to destabilization of the nanotubes. The destabilization of the nanotubes was attributed to the inhomogeneous interaction, non-covalent van der Waals forces, between the nanotubes walls and the inner molecules, which can lead to the tube mechanical instability even at low pressure. In general, optical spectroscopy is a powerful technique to characterize the electronic band structure in terms of the energy position and spectral weight of the excited optical transitions. As demonstrated recently, the optical response is capable of monitoring small pressure-induced deformations of the tubular crosssection, as the characteristic van Hove singularities (vHS) in the density of states in SWCNTs are very sensitive to such deformations. Within the present work, the relevance of PTM regarding the pressure-induced effects in sample under investigation will be clarified. It has been demonstrated previously that fluids, nitrogen or argon as PTM can intercalate inside the SWCNTs, introducing a steric barrier which is responsible for the SWCNTs stabilization against the applies pressure. Therefore, nitrogen, argon, and alcohol mixture as PTM were used to clarify the effect of the different PTM on the stability of the samples under investigations

Graphene Oxide/Polyvinyl Alcohol–Formaldehyde Composite Loaded by Pb Ions: Structure and Electrochemical Performance

An immobilization of graphene oxide (GO) into a matrix of polyvinyl formaldehyde (PVF) foam as an eco-friendly, low cost, superior, and easily recovered sorbent of Pb ions from an aqueous solution is described. The relationships between the structure and electrochemical properties of PVF/GO composite with implanted Pb ions are discussed for the first time. The number of alcohol groups decreased by 41% and 63% for PVF/GO and the PVF/GO/Pb composite, respectively, compared to pure PVF. This means that chemical bonds are formed between the Pb ions and the PVF/GO composite based on the OH groups. This bond formation causes an increase in the Tg values attributed to the formation of a strong surface complexation between adjacent layers of PVF/GO composite. The conductivity increases by about 2.8 orders of magnitude compared to the values of the PVF/GO/Pb composite compared to the PVF. This means the presence of Pb ions is the main factor for enhancing the conductivity where the conduction mechanism is changed from ionic for PVF to electronic conduction for PVF/GO and PVF/GO/Pb

Design of U and I Ferrite Core On Dynamic Wirelesss Charging for Electric Vehicle

This study provides an approach investigation of U and I ferrite core geometrics to improve the power efficiency for Electric Vehicle (EV) inductive wireless charging in dynamic mode. Dynamic wireless charging (DWC) enables recharging of battery pad during the vehicle is on the road. Hence, the design of battery pad must deal with two main factor that led to power leakage such air gap and misalignment. Using ferrite magnetic core, it improves the power transferred by reduce the leakage magnetic radiation between primary and secondary side. Different conditions are investigated on U and I core. The first and second condition is U or I core only at primary side and secondary U or I core only at the secondary side. The last condition is both at primary and secondary side of U or I ferrite core. The purpose of this project is to design a prototype of EV thru several method, design proposed, circuit simulation, pair simulation and prototype development. NI Multisim are used to simulate circuit of WPT for operation validity

Tailored CNTs Buckypaper Membranes for the Removal of Humic Acid and Separation of Oil-In-Water Emulsions

Carbon nanotubes (CNTs) are a robust material and proven as a promising candidate for a wide range of electronic, optoelectronic and environmental applications. In this work, two different methods were utilized for the preparation of CNTs exhibiting different aspect ratios via chemical vapor deposition (CVD). The as-prepared CNTs were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2adsorption isotherms, thermogravimetric analysis and Raman spectroscopy in order to investigate their morphological and structural properties. Free-standing CNTs “buckypaper” membranes were fabricated, characterized and tailored to meet the requirements of two applications, i.e., (1) the removal of humic acid (HA) from water and (2) separation of oil-in-water emulsions. It was revealed that the hydrophobic buckypapers showed high separation performance for Shell oil-in-water emulsions filtration, with up to 98% through the accumulation of oil droplets onto the membrane surface. The absorption capacity of buckypaper membranes for various organic liquids (oil, chloroform and toluene) was evaluated over 10 absorption cycles to investigate their recyclability and robustness. Moreover, surface modification was introduced to the pristine CNTs to increase their surface hydrophilicity and improve the pure water permeability of buckypapers. These modified buckypapers showed high flux for HA solutions and excellent HA rejection efficiency up to 95%via size exclusion and electrostatic repulsion mechanisms

Wet chemistry route for the decoration of carbon nanotubes with iron oxide nanoparticles for gas sensing

In this work, we investigated the parameters for decorating multiwalled carbon nanotubes with iron oxide nanoparticles using a new, inexpensive approach based on wet chemistry. The effect of process parameters such as the solvent used, the amount of iron salt or the calcination time on the morphology, decoration density and nanocluster size were studied. With the proposed approach, the decoration density can be adjusted by selecting the appropriate ratio of carbon nanotubes/iron salt, while nanoparticle size can be modulated by controlling the calcination period. Pristine and iron-decorated carbon nanotubes were deposited on silicon substrates to investigate their gas sensing properties. It was found that loading with iron oxide nanoparticles substantially ameliorated the response towards nitrogen dioxide