Fully inkjet-printed two-dimensional material field-effect heterojunctions for wearable and textile electronics.

Fully printed wearable electronics based on two-dimensional (2D) material heterojunction structures also known as heterostructures, such as field-effect transistors, require robust and reproducible printed multi-layer stacks consisting of active channel, dielectric and conductive contact layers. Solution processing of graphite and other layered materials provides low-cost inks enabling printed electronic devices, for example by inkjet printing. However, the limited quality of the 2D-material inks, the complexity of the layered arrangement, and the lack of a dielectric 2D-material ink able to operate at room temperature, under strain and after several washing cycles has impeded the fabrication of electronic devices on textile with fully printed 2D heterostructures. Here we demonstrate fully inkjet-printed 2D-material active heterostructures with graphene and hexagonal-boron nitride (h-BN) inks, and use them to fabricate all inkjet-printed flexible and washable field-effect transistors on textile, reaching a field-effect mobility of ~91 cm2 V-1 s-1, at low voltage (<5 V). This enables fully inkjet-printed electronic circuits, such as reprogrammable volatile memory cells, complementary inverters and OR logic gates

Ultra-low contact resistance in graphene devices at the Dirac point

Contact resistance is one of the main factors limiting performance of short-channel graphene field-effect transistors (GFETs), preventing their use in low-voltage applications. Here we investigated the contact resistance between graphene grown by chemical vapor deposition (CVD) and different metals, and found that etching holes in graphene below the contacts consistently reduced the contact resistance, down to 23 Omega . mu m with Au contacts. This low contact resistance was obtained at the Dirac point of graphene, in contrast to previous studies where the lowest contact resistance was obtained at the highest carrier density in graphene (here 200 Omega . mu m was obtained under such conditions). The 'holey' Au contacts were implemented in GFETs which exhibited an average transconductance of 940 S m(-1) at a drain bias of only 0.8 V and gate length of 500 nm, which out-perform GFETs with conventional Au contacts

Geometry and field theory in multi-fractional spacetime

We construct a theory of fields living on continuous geometries with fractional Hausdorff and spectral dimensions, focussing on a flat background analogous to Minkowski spacetime. After reviewing the properties of fractional spaces with fixed dimension, presented in a companion paper, we generalize to a multi-fractional scenario inspired by multi-fractal geometry, where the dimension changes with the scale. This is related to the renormalization group properties of fractional field theories, illustrated by the example of a scalar field. Depending on the symmetries of the Lagrangian, one can define two models. In one of them, the effective dimension flows from 2 in the ultraviolet (UV) and geometry constrains the infrared limit to be four-dimensional. At the UV critical value, the model is rendered power-counting renormalizable. However, this is not the most fundamental regime. Compelling arguments of fractal geometry require an extension of the fractional action measure to complex order. In doing so, we obtain a hierarchy of scales characterizing different geometric regimes. At very small scales, discrete symmetries emerge and the notion of a continuous spacetime begins to blur, until one reaches a fundamental scale and an ultra-microscopic fractal structure. This fine hierarchy of geometries has implications for non-commutative theories and discrete quantum gravity. In the latter case, the present model can be viewed as a top-down realization of a quantum-discrete to classical-continuum transition.Comment: 1+82 pages, 1 figure, 2 tables. v2-3: discussions clarified and improved (especially section 4.5), typos corrected, references added; v4: further typos correcte

Introducing a combined pattern to empower risk assessment knowledge of safety, health and environment in health care systems

Background: Knowledge management is the process of using knowledge to achieve intended purposes. Since there are extremely high health, safety and environmental risks in healthcare system, knowledge management not only helps the patient health, but also improves the health and safety of healthcare workers through using proper information and experiences. Methods: In this study, a questionnaire with 11 key questions was developed, Then for the evaluation of validity and consistency of the primarily questionnaire, Inter Rate Agreement and Cronbach &alpha; coefficient were used. Finally based on information collected, data was done by the binominal test with SPSS-22 software. Results: The relevancy (92.7%) and clarity (91.8%) were found to be acceptable, the questionnaire was internally consistent (&alpha;=0.7) and the results of binominal test showed that all questions were accepted (up to 75% for each) by the experts. Conclusion: Although knowledge management is a new area in our country, it is important applying new and beneficial patterns in various aspects of activities like HSE management. Based on obtained results, in can be concluded that the introduced questionnaire is a valid and reliable tool for using in workplace processes

Performance analysis of flexible ink-jet printed humidity sensors based on graphene oxide

This paper presents design, fabrication, and characterization of flexible capacitive graphene oxide (GO) based humidity sensors, which can be used in many applications, such as environmental protection, civil engineering, and agriculture. They consist of interdigitated electrodes ink-jet printed on a polyimide flexible substrate and GO based sensing layer. Measurement setup for testing and characterization was developed in laboratory conditions. The dependence of the capacitance and resistance of the GO based humidity sensors on the percentage of the applied humidity is presented. The main advantage of developed GO based capacitive humidity sensors is very large variation of capacitance, almost five orders of magnitude, compared with the previously demonstrated sensors. The other advantages of the sensors are fast response-recovery time, excellent reproducibility of the measurement results, and use of cost-effective additive ink-jet technology

Performance Analysis of Flexible Ink-Jet Printed Humidity Sensors Based on Graphene Oxide

This paper presents design, fabrication, and characterization of flexible capacitive graphene oxide (GO) based humidity sensors, which can be used in many applications, such as environmental protection, civil engineering, and agriculture. They consist of interdigitated electrodes ink-jet printed on a polyimide flexible substrate and GO based sensing layer. Measurement setup for testing and characterization was developed in laboratory conditions. The dependence of the capacitance and resistance of the GO based humidity sensors on the percentage of the applied humidity is presented. The main advantage of developed GO based capacitive humidity sensors is very large variation of capacitance, almost five orders of magnitude, compared with the previously demonstrated sensors. The other advantages of the sensors are fast response-recovery time, excellent reproducibility of the measurement results, and use of cost-effective additive ink-jet technology

The Frequency of VIM 2, 3, 9, 11 and VIM all among Metallo-beta-Lactamase Producing Pseudomonas aeruginosa

Introduction: Antibiotic resistance crisis has always been a serious problem for human health and many hospitalized patients are affected worldwide. Pseudomonas aeruginosa is a gram-negative pathogen and one of the most common causes of nosocomial infections. The main mechanism of resistance to beta-lactam antibiotics is the presence of metallo-beta-lactamase (MBL) enzymes. Most of the MBL genes are found in plasmids. The aim of this study was to evaluate the frequency of MBL-producing P. aeruginosa isolates caused by VIM-all and VIM 2, 3, 9, 11and16 genes.   Materials & Methods: Antimicrobial susceptibility of 127 clinical isolates of P. aeruginosa was determined using the standard Kirby-Bauer disk diffusion method according to Clinical and Laboratory Standard Institute (CLSI). Combined-disk test was used for phenotypic determination of MBLs-producing isolates. After DNA extraction, VIM-all and in specific, VIM 2, 3, 9, 11 and 16 genes were amplified using PCR method.   Findings: A total Of 127 clinical isolates of P. aeruginosa, 62 isolates (49%) were resistant to imipenem and 31 isolates (24.5%) showed phenotypic evidences of MBL production. Moreover, among imipenem resistant strains VIM-all genes were found in 12.5% of cases, but the VIM 2-3-9-11 and 16 genes were not detected in samples.   Discussion & Conclusions: The results obtained in this study suggest that in P. aeruginosa, the highest antibiotic resistance observed was to cefazolin (98%) followed by nalidixic acid (91%) and the least resistance were to ciprofloxacin (31%). One of the reasons for this trend is the growth of antibiotic-resistant bacteria and the known mechanisms of bacterial resistance

Characterization of the Intrinsic and Extrinsic Resistances of a Microwave Graphene FET Under Zero Transconductance Conditions

Graphene field-effect transistors (GFETs) exhibit negligible transconductance under two scenarios: for any gate-to-source voltage when the drain-to-source voltage is set to zero and for an arbitrary drain-to-source voltage provided that the gate-to-source voltage equals the Dirac voltage. Hence, extracting the channel and the parasitic series resistances from S-parameters under these conditions enables analyzing their dependence on the gate and drain biases. This is fundamental to assess the portion of the output resistance that is controlled by the gate. Besides, the drain bias dependence of the drain and source resistances is also evidenced. Within the proposal, resistive components accounting for the lossy nature of the gate capacitance are incorporated into the model, which exhibits a broadband correlation with experimental data. This avoids the series resistances to be considered as frequency dependent in the model