Fabrication and Thermoelectric Characterization of Transition Metal Silicide-Based Composite Thermocouples

Metal silicide-based thermocouples were fabricated by screen printing thick films of the powder compositions onto alumina tapes followed by lamination and sintering processes. The legs of the embedded thermocouples were composed of composite compositions consisting of MoSi2, WSi2, ZrSi2, or TaSi2 with an additional 10 vol % Al2O3 to form a silicide–oxide composite. The structural and high-temperature thermoelectric properties of the composite thermocouples were examined using X-ray diffraction, scanning electron microscopy and a typical hot–cold junction measurement technique. MoSi2-Al2O3 and WSi2-Al2O3 composites exhibited higher intrinsic Seebeck coefficients (22.2–30.0 μV/K) at high-temperature gradients, which were calculated from the thermoelectric data of composite//Pt thermocouples. The composite thermocouples generated a thermoelectric voltage up to 16.0 mV at high-temperature gradients. The MoSi2-Al2O3//TaSi2-Al2O3 thermocouple displayed a better performance at high temperatures. The Seebeck coefficients of composite thermocouples were found to range between 20.9 and 73.0 μV/K at a temperature gradient of 1000 ◦C. There was a significant difference between the calculated and measured Seebeck coefficients of these thermocouples, which indicated the significant influence of secondary silicide phases (e.g., Mo5Si3, Ta5Si3) and possible local compositional changes on the overall thermoelectric response. The thermoelectric performance, high sensitivity, and cost efficiency of metal silicide–alumina ceramic composite thermocouples showed promise for high-temperature and harsh-environment sensing applications

Roadmap on printable electronic materials for next-generation sensors

The dissemination of sensors is key to realizing a sustainable, ‘intelligent’ world, where everyday objects and environments are equipped with sensing capabilities to advance the sustainability and quality of our lives—e.g., via smart homes, smart cities, smart healthcare, smart logistics, Industry 4.0, and precision agriculture. The realization of the full potential of these applications critically depends on the availability of easy-to-make, low-cost sensor technologies. Sensors based on printable electronic materials offer the ideal platform: they can be fabricated through simple methods (e.g., printing and coating) and are compatible with high-throughput roll-to-roll processing. Moreover, printable electronic materials often allow the fabrication of sensors on flexible/stretchable/biodegradable substrates, thereby enabling the deployment of sensors in unconventional settings. Fulfilling the promise of printable electronic materials for sensing will require materials and device innovations to enhance their ability to transduce external stimuli—light, ionizing radiation, pressure, strain, force, temperature, gas, vapours, humidity, and other chemical and biological analytes. This Roadmap brings together the viewpoints of experts in various printable sensing materials—and devices thereof—to provide insights into the status and outlook of the field. Alongside recent materials and device innovations, the roadmap discusses the key outstanding challenges pertaining to each printable sensing technology. Finally, the Roadmap points to promising directions to overcome these challenges and thus enable ubiquitous sensing for a sustainable, ‘intelligent’ world

Solar Cells

The second book of the four-volume edition of "Solar cells" is devoted to dye-sensitized solar cells (DSSCs), which are considered to be extremely promising because they are made of low-cost materials with simple inexpensive manufacturing procedures and can be engineered into flexible sheets. DSSCs are emerged as a truly new class of energy conversion devices, which are representatives of the third generation solar technology. Mechanism of conversion of solar energy into electricity in these devices is quite peculiar. The achieved energy conversion efficiency in DSSCs is low, however, it has improved quickly in the last years. It is believed that DSSCs are still at the start of their development stage and will take a worthy place in the large-scale production for the future

A Highly Thermostable In2O3/ITO Thin Film Thermocouple Prepared via Screen Printing for High Temperature Measurements

An In2O3/ITO thin film thermocouple was prepared via screen printing. Glass additives were added to improve the sintering process and to increase the density of the In2O3/ITO films. The surface and cross-sectional images indicate that both the grain size and densification of the ITO and In2O3 films increased with the increase in annealing time. The thermoelectric voltage of the In2O3/ITO thermocouple was 53.5 mV at 1270 °C at the hot junction. The average Seebeck coefficient of the thermocouple was calculated as 44.5 μV/°C. The drift rate of the In2O3/ITO thermocouple was 5.44 °C/h at a measuring time of 10 h at 1270 °C

Low-cost pH sensors based on discrete PCB ion-sensitive field effect transistors

Diagnostic technologies will play a critical role in addressing current and future healthcare challenges, with the greatest impact through implementing these technologies at the point of care (PoC). For truly widespread deployment, these PoC technologies should be low-cost and amenable for mass manufacture, even in resource-limited settings, without compromising analytical performance. Discrete, extended gate pH-sensitive field-effect transistors (dEGFETs) fabricated on widely used printed circuit boards (PCBs) are a low-cost, simple to manufacture analytical technology. Electrodeposited iridium oxide (IrOx) films have emerged as a promising pH-sensitive transducer due to their facile deposition. While IrOx is predicted to have a beyond-Nernstian pH sensitivity, the performance measured experimentally is typically lower and variable. This thesis demonstrates a dEGFET pH sensor based on PCB extended gate electrodes and electrodeposited IrOx, which repeatedly displays beyond-Nernstian pH response. Using complementary surface-analysis techniques, it is shown the high pH sensitivity and repeatability is determined both by the chemical composition and critically the uniformity of the IrOx film. Electrochemical polishing of the extended gate electrode prior to electrodeposition enhances IrOx uniformity, leading to a median pH sensitivity of 70.7 ± 5 mV/pH (n=56) compared to 31.3 ± 14 mV/pH (n=31) for non-polished electrodes. The applicability of these devices is demonstrated through the quantification of the β-lactam antibiotic ampicillin, via the pH change that occurs due to hydrolysis catalysed by β-lactamase enzymes. This lays the foundations for a susceptibility assay towards the public health challenge of antimicrobial resistance (AMR). Additionally, this thesis explores the integration of electronically controlled microfluidic valves onto the PCB substrates, towards the development of lab-on-chip systems and PoC diagnostics. The highly sensitive and repeatable dEGFET sensors presented here show great promise as a low-cost diagnostic technology. Moreover, the use of PCB substrates is suitable for manufacture in resource-limited settings, enabling widespread diagnostic testing