Investigation of shock waves in explosive blasts using fibre optic pressure sensors

The published version of this article may be accessed at the link below. Copyright @ IOP Publishing, 2006.We describe miniature all-optical pressure sensors, fabricated by wafer etching techniques, less than 1 mm(2) in overall cross-section with rise times in the mu s regime and pressure ranges typically 900 kPa (9 bar). Their performance is suitable for experimental studies of the pressure-time history for test models exposed to shocks initiated by an explosive charge. The small size and fast response of the sensors promises higher quality data than has been previously available from conventional electrical sensors, with potential improvements to numerical models of blast effects. Results from blast tests are presented in which up to six sensors were multiplexed, embedded within test models in a range of orientations relative to the shock front.Support from the UK Engineering&Physical Sciences Research Council and Dstl Fort Halstead through the MoD Joint Grants Scheme are acknowledged. WN MacPherson is supported by an EPSRC Advanced Research Fellowship

Micro-fabricated caesium vapour cell with 5mm optical path length

Micro-fabricated vapour cells have applications in a number of emerging quantum technology based devices including miniaturized atomic magnetometers, atomic clocks and frequency references for laser systems. Increasing the cell optical path length (OPL) and smallest cell dimension is normally desirable to increase the signal to noise ratio (SNR) and minimize the de-polarization rate due to collisions between atomic or molecular species and the cell walls. This paper presents a fully wafer-level scalable fabrication process to manufacture vapour cells with dimensions approaching those of glass-blown cells. The fabrication process is described and spectroscopic measurements (optical absorption and magnetic resonance) are reported. A magnetic resonance linewidth of 350 Hz is demonstrated, this is the smallest linewidth reported to date for a micro-fabricated vapour cell

Glazed spaces for a resource efficient, social and healthy living, Part 1. Inventory of geometries and functions by study visits and interviews

The main aim of the Spaces project is to support architects in the design of well-functioning glazed geometries, such as atria and rooftops, in residential buildings. The studied geometries are primarily spaces for communication and leisure in residential buildings. These spaces may have a varying indoor climate, which is governed by the construction of the building, as well as residents’ activities, rather than by building services. The project contributes with examples of geometries and usages, methods to evaluate the performance early in the design process and to provide guidance for architectural design and increased social interaction. The project also investigates obstacles that exist in current practice and Swedish legislation for glazed geometries.In this report, the first part of the project “Inventory of geometries and functions by study visits and interviews” is presented. Methods used in this first part is literature studies, interviews and case studies. The topics investigated are social and human aspects, technical aspects such as thermal comfort, energy, air quality, humidity, acoustics and to some extent urban farming. From the literature and by contacting architects and consultants in the building industry, eight case study buildings were found, located. The buildings were either housing cooperatives or rental buildings, and the glazed spaces in the buildings were either atria, glazed balconies or glazed rooftops.For the case studies, information was gathered from databases, through interviews and during study visits. The opinions of the residents were captured during structured interviews and through quantifiable surveys, and the results were analysed by the project group with input from the reference group.For social interaction, the investigations show that even with a developed design for social interaction (such as common areas, kindergarden, private areas in connection with glazed space), the interaction might fail. Social activities are highly dependent on individuals and thus, engaged persons are very valuable to obtain a social environment. In addition, a clear purpose of the space and a sense of ownership is beneficial to the social environment. In this study, the projects that worked well socially were the four housing cooperatives and one rental building. The three projects that worked less well were all rental.There are slightly different opinions of the optimal size to achieve social interaction. The architect of one of the projects that works well socially suggests a maximum of 60 persons (25-30 families) and at another socially successful building, there are 48 apartments. Two out of the three largest buildings (71 apartments and 126 apartments) did not function well socially.Daylight levels are usually considered good in the glazed spaces. However, there are darker areas, in particular under access balconies, and this also affects the daylight levels in the apartments. The air quality is usually perceived as good in the glazed spaces and the most common problem connected to air quality is a high level of moisture in the air, which can result in condensation on windows.For thermal comfort, the expected level of comfort is important for the experience of the space. If the space looks like it is indoor, the expectation is room temperature in wintertime and, consequently, people are disappointed if it’s much colder. Both studied rooftops have problems with high temperatures in summertime. The temperature in the glazed space depends to a large degree on shading and ventilation, but also on the thermal mass of the materials in the glazed space. This is further investigated in part 2 of the project (Wahlgren et al. 2021), where also evaluation tools and design guidelines are presented

Test Structures for Developing Packaging for Implantable Sensors

With their capacity for real time monitoring and spatial mapping, implantable sensors are becoming an increasingly important aspect of next generation precision healthcare. Microfabricated sensor systems are a popular choice, owing to their capacity for miniaturisation, repeatable mass manufacture, and numerous pre-existing sensor archetypes. Despite the drive for development, packaging these sensors for the environment within the body, as well as the implantation process itself, presents a significant challenge. This paper presents microelectronic test structures, which can be used to assess, compare, and optimise implantable packaging solutions in a standardised manner. The proposed structures are used to investigate: (i) the capacity of the material to be patterned, (ii) the permeability of the insulation material, (iii) adhesion of the encapsulant to the die, and (iv) the physical robustness of the package to implantation through a needle. They are used to characterise an example packaging strategy, using biocompatible epoxy-resin. In addition, a method of optimising the packaging performance using the test structures is presented

Integration of ZnO nanowires with coupled resonators for ammonia gas detection

This study presents a novel ammonia sensor using hydro-thermally synthesized ZnO nanowires integrated with a mode-localized coupled resonator. The ZnO nanowires, with their high sur-face area, act as an efficient gas adsorption layer. The resonator’s driving mechanism was optimized using finite element method (FEM) simulations, revealing that a coupled resonator pair exhibited 45.52 times higher sensitivity than a single resonator. Out-of-phase modes showed greater sensitivity than in-phase modes. Resonators R1 and R2 driven together had the lowest sensitivity, while Resonator 1, with a zinc oxide layer and driven individually, demonstrated the highest sensitivity. Additionally, the sensitivity of the coupled resonator in-creased with the decrease in DC bias voltage. Comprehensive mate-rials characterization of the ZnO nanowires was conducted using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to confirm their structural and chemical properties. Fourier-transform infrared spectroscopy (FTIR) results showed that after ammonia adsorption, zinc oxide nanowires exhibited additional absorption bands at approximately 1430 cm−1, 1633 cm−1, and within the broad range of 3100 to 3550 cm−1. The sensor’s gas-sensing performance was evaluated with varying ammonia concentrations, achieving a very high sensitivity of 0.0026 ppm−1 in the 25–100 ppm range at room temperature. This design highlights the potential of integrating ZnO nanowires with modal-coupled resonators for highly sensitive, miniaturized, low-cost sensors for environmental monitoring and safety applications

Comparison of Conventional and Maskless Lithographic Techniques for More than Moore Post-processing of Foundry CMOS Chips

This article details and compares the technology options for post-processing foundry produced CMOS at chip-scale to enable More than Moore functionality. In many cases there are attractions in using chip-based processing through the Multi-Project Wafer route that is frequently employed in research, early-stage development and low-volume production. This article identifies that spray-based photoresist deposition combined with optical maskless lithography demonstrates sufficient performance combined with low cost and operational convenience to offer an attractive alternative to conventional optical lithography, where spin-coated photoresist is exposed through a patterned photomask. [2020-0249

Fabrication and characterisation of suspended microstructures of tantalum

Funding: UK Engineering and Physical Sciences Research Council (EPSRC).An investigation of the influence of deposition and post-fabrication processes on the final mechanical structure of tantalum beams is reported in the present study. The final deflection profiles of doubly supported beams made from compressive and tensile-stressed films have been studied experimentally. An optimum finite element model has been developed to predict the buckling behaviour of the doubly supported beams by considering the boundary conditions in the form of a compressive stress and an applied load. No matter which etch release method has been used, the initial stress state of the as-deposited films has been found to have a significant impact on the final deflection profile of the fabricated device. The compressive-stressed films have presented larger deflection in the final released beams than the tensile-stressed films. Taking into account the type of etch release methods, the beams that have been released in the dry etch release processes have been found to deform more vertically than those released in the wet-etch release method. Moreover, it has been found that the amplitude of vertical deflection increases with the increase of the beam length and thickness. The results indicate that optimum profiles of tantalum suspended structures can be obtained from the tensile-stressed films that have been released by the wet etching method with an aspect ratio of 1:48.Publisher PDFPeer reviewe

Optimization of Nafion Polymer Electrolyte Membrane Design and Microfabrication

Nafion is a solid electrolyte polymer that can be used as a sensor membrane in microfabricated electrochemical oxygen sensors. It allows ions to be transported between the sensor electrodes and removes the need for a liquid electrolyte. Here we used a series of small square Nafion test structures, fabricated on a variety of materials using standard thin-film patterning techniques, to optimize the design and processing of Nafion membranes. Measurements showed that the choice of photoresist developer is critical. Use of diluted MF-26A developer provided the most effective and manufacturable process. The underlying material also had an influence on robustness, with silicon dioxide and platinum giving the longest membrane lifetime under simulated conditions of use. Membrane size had no clear effect on lifetime, and under optimal processing conditions there were minimal failures even under continuous mechanical agitation for up to six weeks. We also developed test electrodes covered by Nafion, and showed that they were effective at supporting electrochemical oxygen detection

In vivo validation of a miniaturized electrochemical oxygen sensor for measuring intestinal oxygen tension

Recent advances in the fields of electronics and microfabrication techniques have led to the development of implantable medical devices for use within the field of precision medicine. Monitoring visceral surface tissue O2 tension (ptO2) by means of an implantable sensor is potentially useful in many clinical situations including the peri-operative management of patients undergoing intestinal resection and anastomosis. This concept could provide a means by which treatment could be tailored to individual patients. This study describes the in vivo validation of a novel miniaturised electrochemical O2 sensor to provide real-time data on intestinal ptO2. A single O2 sensor was placed onto the serosal surface of the small intestine of anaesthetised rats that were exposed to ischaemic (superior mesenteric artery occlusion) and hypoxaemic (alterations in inspired fractional O2 concentrations) insults. Control experiments demonstrated that the sensors function and remain stable in an in vivo environment. Intestinal ptO2 decreased following superior mesenteric artery occlusion and with reductions in inspired O2 concentrations. These results were reversible after reinstating blood flow or increasing inspired O2 concentrations. We have successfully developed an anaesthetised rat intestinal ischaemic and hypoxic model for validation of a miniaturised O2 sensor to provide real-time measurement of intestinal ptO2. Our results support further validation of the sensors in physiological conditions using a large animal model to provide evidence of their use in clinical applications where monitoring visceral surface tissue O2 tension is important