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1.
ACS Appl Mater Interfaces ; 11(23): 21166-21176, 2019 Jun 12.
Artigo em Inglês | MEDLINE | ID: mdl-31063352

RESUMO

Natural fibers composites are considered as a sustainable alternative to synthetic composites due to their environmental and economic benefits. However, they suffer from poor mechanical and interfacial properties due to a random fiber orientation and weak fiber-matrix interface. Here we report nanoengineered graphene-based natural jute fiber preforms with a new fiber architecture (NFA) which significantly improves their mechanical properties and performances. Our graphene-based NFA of jute fiber preform enhances the Young modulus of jute-epoxy composites by ∼324% and tensile strength by ∼110% more than untreated jute fiber composites, by arranging fibers in a parallel direction through individualization and nanosurface engineering with graphene derivatives. This could potentially lead to manufacturing of high-performance natural alternatives to synthetic composites in various stiffness-driven applications.

2.
Sci Rep ; 9(1): 8035, 2019 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-31142768

RESUMO

Inkjet-printed wearable electronic textiles (e-textiles) are considered to be very promising due to excellent processing and environmental benefits offered by digital fabrication technique. Inkjet-printing of conductive metallic inks such as silver (Ag) nanoparticles (NPs) are well-established and that of graphene-based inks is of great interest due to multi-functional properties of graphene. However, poor ink stability at higher graphene concentration and the cost associated with the higher Ag loading in metal inks have limited their wider use. Moreover, graphene-based e-textiles reported so far are mainly based on graphene derivatives such as graphene oxide (GO) or reduced graphene oxide (rGO), which suffers from poor electrical conductivity. Here we report inkjet printing of highly conductive and cost-effective graphene-Ag composite ink for wearable e-textiles applications. The composite inks were formulated, characterised and inkjet-printed onto PEL paper first and then sintered at 150 °C for 1 hr. The sheet resistance of the printed patterns is found to be in the range of ~0.08-4.74 Ω/sq depending on the number of print layers and the graphene-Ag ratio in the formulation. The optimised composite ink was then successfully printed onto surface pre-treated (by inkjet printing) cotton fabrics in order to produce all-inkjet-printed highly conductive and cost-effective electronic textiles.

3.
ACS Nano ; 13(4): 3847-3857, 2019 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-30816692

RESUMO

Multifunctional wearable e-textiles have been a focus of much attention due to their great potential for healthcare, sportswear, fitness, space, and military applications. Among them, electroconductive textile yarn shows great promise for use as next-generation flexible sensors without compromising the properties and comfort of usual textiles. However, the current manufacturing process of metal-based electroconductive textile yarn is expensive, unscalable, and environmentally unfriendly. Here we report a highly scalable and ultrafast production of graphene-based flexible, washable, and bendable wearable textile sensors. We engineer graphene flakes and their dispersions in order to select the best formulation for wearable textile application. We then use a high-speed yarn dyeing technique to dye (coat) textile yarn with graphene-based inks. Such graphene-based yarns are then integrated into a knitted structure as a flexible sensor and could send data wirelessly to a device via a self-powered RFID or a low-powered Bluetooth. The graphene textile sensor thus produced shows excellent temperature sensitivity, very good washability, and extremely high flexibility. Such a process could potentially be scaled up in a high-speed industrial setup to produce tonnes (∼1000 kg/h) of electroconductive textile yarns for next-generation wearable electronics applications.

4.
Conf Proc IEEE Eng Med Biol Soc ; 2019: 6693-6696, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31947377

RESUMO

We present a new wearable electrooculogram (EOG) monitor for measuring eye movements. We fabricated conductive and flexible graphene-based textiles from nylon to use as a sensing electrode, which we then integrated into a commercially available eye mask held in place only with the standard elastic strap. We tested this mask on 4 participants to quantify the noise floor and show that we can detect eye blinks to a high SNR of over 16 dB. We also identify that the material can detect other eye movements in cases when the noise floor is low. As our system is held in place with only an elastic strap it offers the same level of comfort as when wearing a normal eye mask. Our sensors offer an increased level of comfort over conventional gelled electrodes traditionally used in EOG monitoring and may be of use for comfortable eye movement experiments. This is particularly important during sleep studies where the EOG is routinely monitored, but using bulky instrumentation.

5.
Conf Proc IEEE Eng Med Biol Soc ; 2018: 3813-3816, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-30441196

RESUMO

Smart garments for invisible health sensing have been available for a number of years, with heart sensing typically performed using silver loaded conductive threads integrated into the fabric to pick up the electrocardiogram. Recent work has investigated printed graphene textiles as an alternative to this, which are potentially more environmentally friendly, cost-effective, and can be performed after garment manufacturing. This paper presents an exploration of second order factors on the performance of graphene textile electrodes for electrocardiogram measurements. We prepare graphenebased textile electrodes using a simple and highly scalable continuous padding method. We then analyze two metrics: the change in heart rate estimation error, and the changes in signal-to-noise ratio; under two separate conditions: an extended record length, and varying temperatures; to recreate the some of the conditions the material would experience when being worn in real-life. We report that neither the heart rate estimation error or the signal-to-noise ratio are significantly affected after a long record or with varying temperature. These tests indicate that graphene electrodes are suitable for electrocardiogram measurements in a wearable that will be subjected to these conditions.


Assuntos
Eletrocardiografia , Eletrodos , Grafite , Têxteis , Coração , Humanos , Razão Sinal-Ruído
6.
ACS Appl Mater Interfaces ; 10(40): 34502-34512, 2018 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-30222307

RESUMO

Natural fiber composites are attracting significant interest due to their potential for replacing synthetic composites at lower cost with improved environmental sustainability. However, natural fiber composites suffer from poor mechanical and interfacial properties. Here, we report coating of graphene oxide (GO) and graphene flakes (G) onto natural jute fibers to improve mechanical and interfacial properties. The coating of graphene materials onto jute fibers enhanced interfacial shear strength by ∼236% and tensile strength by ∼96% more than untreated fibers by forming either bonding (GO) or mechanical interlocking (G) between fibers and graphene-based flakes. This could lead to manufacturing of high-performance and environmental friendly natural fiber composites that can potentially replace synthetic composites in numerous applications, such as the automotive industry, naval vessels, household products, and even in the aerospace industry.

7.
ACS Nano ; 11(12): 12266-12275, 2017 12 26.
Artigo em Inglês | MEDLINE | ID: mdl-29185706

RESUMO

Graphene-based wearable e-textiles are considered to be promising due to their advantages over traditional metal-based technology. However, the manufacturing process is complex and currently not suitable for industrial scale application. Here we report a simple, scalable, and cost-effective method of producing graphene-based wearable e-textiles through the chemical reduction of graphene oxide (GO) to make stable reduced graphene oxide (rGO) dispersion which can then be applied to the textile fabric using a simple pad-dry technique. This application method allows the potential manufacture of conductive graphene e-textiles at commercial production rates of ∼150 m/min. The graphene e-textile materials produced are durable and washable with acceptable softness/hand feel. The rGO coating enhanced the tensile strength of cotton fabric and also the flexibility due to the increase in strain% at maximum load. We demonstrate the potential application of these graphene e-textiles for wearable electronics with activity monitoring sensor. This could potentially lead to a multifunctional single graphene e-textile garment that can act both as sensors and flexible heating elements powered by the energy stored in graphene textile supercapacitors.

8.
Int J Nephrol ; 2016: 7126290, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27493801

RESUMO

Introduction. Postrenal transplant bone disease is a significant problem. Factors influencing postrenal transplant bone status include high dose acute and low dose long-term steroid use, persistent hypercalcaemia, and graft failure. In this study, we aimed to determine the prevalence of hypercalcaemia and to evaluate the risk factors for postrenal transplant hypercalcaemia in long-term renal transplant patients at our centre. Methods. This is a biochemical audit in which we studied renal transplant recipients from the Central Northern Adelaide Renal Transplant Services, South Australia. Inclusion criteria include kidney transplant patients with functioning graft since 1971 and at least 3 months after transplantation at the time of analysis. Hypercalcaemia was defined as persistently elevated serum corrected calcium greater than or equal to 2.56 mmol/L for three consecutive months. Results. 679 renal transplant recipients with a functioning graft were studied and 101 were hypercalcaemic between March 2011 and June 2011 (15%). 60% of the hypercalcaemic patients were male and 40% were female, with chronic glomerulonephritis (39%) being the commonest cause of their end stage kidney disease (ESKD). Prevalence was similar in those that had haemodialysis and peritoneal dialysis pretransplantation. Hypercalcaemia in the renal transplant population was not secondary to suboptimal allograft function but secondary to pretransplantation hyperparathyroidism with persistent high parathyroid hormone (PTH) levels after transplantation. Conclusion. There is a high prevalence of hypercalcaemia (15%) in renal transplant recipients. The predominant cause for hypercalcaemia is pretransplantation hyperparathyroidism. The magnitude of pretransplantation hyperparathyroidism is the major determinant for long-term parathyroid function rather than graft function or pretransplantation duration on dialysis or mode of dialysis.

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