This paper presents the performance of a passive planar rhombic micromixer with diamond-shaped obstacles and a rectangular contraction between the rhombi. The device was experimentally optimized using water for high mixing efficiency and a low pressure drop over a wide range of Reynolds numbers (Re = 0.1–117.6) by varying geometrical parameters such as the number of rhombi, the distance between obstacles and the contraction width. Due to the large amount of data generated, statistical methods were used to facilitate and improve the results of the analysis. The results revealed a rank of factors influencing mixing efficiency: Reynolds number {\textgreater} number of rhombi {\textgreater} contraction width {\textgreater} inter-obstacles distance. The pressure drop measured after three rhombi depends mainly on Re and inter-obstacle distance. The resulting optimum geometry for the low Re regime has a contraction width of 101 $μ$m and inter-obstacles distance of 93 $μ$m, while for the high Re regime a contraction width of 400 $μ$m and inter-obstacle distance of 121 $μ$m are more appropriate. These mixers enabled 80{%} mixing efficiency creating a pressure drop of 6.0 Pa at Re = 0.1 and 5.1 × 104 Pa at Re = 117.6, with a mixer length of 2.5 mm. To the authors' knowledge, the developed mixer is one of the shortest planar passive micromixers reported to date.

The degradation of thin-film transistors (TFTs) caused by the self-heating effect constitutes a problem to be solved for the next generation of displays. Aluminum nitride (AlN) is a viable alternative for gate dielectric of TFTs due to its good thermal conductivity, matching coefficient of thermal expansion to indium–gallium–zinc-oxide, and excellent stability at high temperatures. Here, AlN thin films of different thicknesses were fabricated by a low temperature reactive radio-frequency magnetron sputtering process, using a low cost, metallic Al target. Their electrical properties have been thoroughly assessed. Furthermore, the 200 nm and 500 nm thick AlN layers have been integrated as gate-dielectric in transparent TFTs with indium–gallium–zinc-oxide as channel semiconductor. Our study emphasizes the potential of AlN thin films for transparent electronics, whilst the functionality of the fabricated field-effect transistors is explored and discussed.

Solution processing has been recently considered as an option when trying to reduce the costs associated with deposition under vacuum. In this context, most of the research efforts have been centered in the development of the semiconductors processes nevertheless the development of the most suitable dielectrics for oxide based transistors is as relevant as the semiconductor layer itself. In this work we explore the solution combustion synthesis and report on a completely new and green route for the preparation of amorphous aluminum oxide thin films; introducing water as solvent. Optimized dielectric layers were obtained for a water based precursor solution with 0.1 M concentration and demonstrated high capacitance, 625 nF cm(-2) at 10 kHz, and a permittivity of 7.1. These thin films were successfully applied as gate dielectric in solution processed gallium-zinc-tin oxide (GZTO) thin film transistors (TFTs) yielding good electrical performance such as subthreshold slope of about 0.3 V dec(-1) and mobility above 1.3 cm(2) V(-1) s(-1).

Aluminium-doped zinc oxide (AZO) is a common material used as a front contact layer on chalcopyrite CuInGaSe2 (CIGS)-based thin-film solar cells since it combines optimum optical and electrical properties with low cost and abundant elemental availability. Low-resistivity and high-transmission front contacts are required to develop high-performance CIGS solar cells. However, the durability of the cells is highly influenced by the corrosion resistance behaviour of the AZO layers. In this work, an exhaustive study of the aluminium-doped zinc oxide layers (AZO) deposited by pulsed DC magnetron sputtering (MS) has been performed. The optical, electrical and electrochemical corrosion resistance properties of the AZO layers have been evaluated as a function of the deposition pressure. The results show that adjusting the deposition pressure could develop AZO layers with very high electrochemical corrosion resistance in chlorinated aqueous media combined with optimum electrical and optical properties. Layers grown at 3×10−3mbar pressure present very high corrosion resistance values (in the order of 106 {\$}Ømega{\$}) and very high electrochemical stability, indicating no tendency for electrochemical corrosion degradation. Besides, these layers are highly transparent with an average transmittance in the visible range above 90{%} and with a low resistivity of 6.8×10−4 {\$}Ømega{\$}cm for a 1000nm films thickness, making them optimum candidate front contact for high-performance and high durability CIGS solar cells.

Cotton-based nanocrystalline cellulose (NCC), also known as nanopaper, one of the major sources of renewable materials, is a promising substrate and component for producing low cost fully recyclable flexible paper electronic devices and systems due to its properties (lightweight, stiffness, non-toxicity, transparency, low thermal expansion, gas impermeability and improved mechanical properties). Here, we have demonstrated for the first time a thin transparent nanopaper-based field effect transistor (FET) where NCC is simultaneously used as the substrate and as the gate dielectric layer in an ‘interstrate' structure, since the device is built on both sides of the NCC films; while the active channel layer is based on oxide amorphous semiconductors, the gate electrode is based on a transparent conductive oxide. Such hybrid FETs present excellent operating characteristics such as high channel saturation mobility ({\textgreater}7 cm 2 V −1 s −1 ), drain–source current on/off modulation ratio higher than 10 5 , enhancement n-type operation and subthreshold gate voltage swing of 2.11 V/decade. The NCC film FET characteristics have been measured in air ambient conditions and present good stability, after two weeks of being processed, without any type of encapsulation or passivation layer. The results obtained are comparable to ones produced for conventional cellulose paper, marking this out as a promising approach for attaining high-performance disposable electronics such as paper displays, smart labels, smart packaging, RFID (radio-frequency identification) and point-of-care systems for self-analysis in bioscience applications, among others.

In this study, we report solution-processed amorphous zinc tin oxide transistors exhibiting high operational stability under positive gate bias stress, translated by a recoverable threshold voltage shift of about 20{%} of total applied stress voltage. Under vacuum condition, the threshold voltage shift saturates showing that the gate-bias stress is limited by trap exhaustion or balance between trap filling and emptying mechanism. In ambient atmosphere, the threshold voltage shift no longer saturates, stability is degraded and the recovering process is impeded. We suggest that the trapping time during the stress and detrapping time in recovering are affected by oxygen adsorption/desorption processes. The time constants extracted from stretched exponential fitting curves are ≈106 s and 105 s in vacuum and air, respectively.

We reported here ?aqueous-route? fabrication of In2O3 thin-film transistors (TFTs) using an ultrathin solution-processed ZrOx dielectric thin film. The formation and properties of In2O3 thin films under various annealing temperatures were intensively examined by thermogravimetric analysis, Fourier transform infrared spectroscopy, and atomic force microscopy. The solution-processed ZrOx thin film followed by sequential UV/ozone treatment and low-temperature thermal-annealing processes showed an amorphous structure, a low leakage-current density (?1 ? 10?9 A/cm2 at 2 MV/cm), and a high breakdown electric field (?7.2 MV/cm). On the basis of its implementation as the gate insulator, the In2O3 TFTs based on ZrOx annealed at 250 °C exhibit an on/off current ratio larger than 107, a field-effect mobility of 23.6 cm2/V·s, a subthreshold swing of 90 mV/decade, a threshold voltage of 0.13 V, and high stability. These promising properties were obtained at a low operating voltage of 1.5 V. These results suggest that ?aqueous-route? In2O3 TFTs based on a solution-processed ZrOx dielectric could potentially be used for low-cost, low-temperature-processing, high-performance, and flexible devices.

In this study, we report high-performance amorphous In2O3/InZnO bilayer metal-oxide (BMO) thin-film transistor (TFT) using an ultra-thin solution-processed amorphous ZrOx dielectric. A thin layer of In2O3 offers a higher carrier concentration, thereby maximizing the charge accumulation and yielding high carrier mobility. A thick amorphous layer of InZnO controls the charge conductance resulting in low off-state current and suitable threshold voltage. As a consequence, the BMO TFT showed higher filed-effect mobility (37.9 cm2/V s) than single-layer InZnO TFT (7.6 cm2/V s). Apart from that we obtain an on/off current ratio of 109, a subthreshold swing voltage of 120 mV/decade, and a voltage shift ≤ 0.4 V under positive bias stress for 2.5 h, for a gate voltage of 3 V and drain voltage of 1 V. These data demonstrate that the BMO TFT has great potential for a broad range of applications as switching low-power transistors.

Electrochemically active bacteria (EAB) have the capability to transfer electrons to cell exterior, a feature that is currently explored for important applications in bioremediation and biotechnology fields. However, the number of isolated and characterized EAB species is still very limited regarding their abundance in nature. Colorimetric detection has emerged recently as an attractive mean for fast identification and characterization of analytes based on the use of electrochromic materials. In this work, WO3 nanoparticles were synthesized by microwave assisted hydrothermal synthesis and used to impregnate non-treated regular office paper substrates. This allowed the production of a paper-based colorimetric sensor able to detect EAB in a simple, rapid, reliable, inexpensive and eco-friendly method. The developed platform was then tested with Geobacter sulfurreducens, as a proof of concept. G. sulfurreducens cells were detected at latent phase with an RGB ratio of 1.10 ± 0.04, and a response time of two hours.