Kenneth Rodgers

Rapid fabrication of microfluidic devices in poly(dimethylsiloxane) by photocopying

A very simple and fast method for the fabrication of poly(dimethylsiloxane) (PDMS) microfluidic devices is introduced. By using a photocopying machine to make a master on transparency instead of using lithographic equipment and photoresist, the fabrication process is greatly simplified and speeded up, requiring less than 1.5 h from design to device. Through SEM characterization, any micro-channel network with a width greater than 50 microm and a depth in the range of 8-14 microm can be made by this method. After sealing to a Pyrex glass plate with micromachined platinum electrodes, a microfluidic device was made and the device was tested in FIA mode with on-chip conductometric detection without using either high voltage or other pumping methods.

Voltammetric characterisation of silicon-based microelectrode arrays and their application to mercury-free stripping voltammetry of copper ions.

This paper describes the electrochemical characterisation of a range of gold and platinum microelectrode arrays (MEAs) fabricated by standard photolithographic methods. The inter-electrode spacing, geometry, numbers and dimensions of the electrodes in the arrays were found to influence the voltammetric behaviours obtained. Excellent correlation was found between experimental data and theoretical predictions employing published models of microelectrode behaviour. Gold MEAs were evaluated for their applicability to copper determination in a soil extract sample, where agreement was found between the standard analytical method and a method based on underpotential deposition-anodic stripping voltammetry (UPD-ASV) at the MEAs, offering a mercury-free alternative for copper sensing.

Single Nanoskived Nanowires for Electrochemical Applications

In this work, we fabricate gold nanowires with well controlled critical dimensions using a recently demonstrated facile approach termed nanoskiving. Nanowires are fabricated with lengths of several hundreds of micrometers and are easily electrically contacted using overlay electrodes. Following fabrication, nanowire device performance is assessed using both electrical and electrochemical characterization techniques. We observe low electrical resistances with typical linear Ohmic responses from fully packaged nanowire devices. Steady-state cyclic voltammograms in ferrocenemonocarboxylic acid demonstrate scan rate independence up to 1000 mV s(-1). Electrochemical responses are excellently described by classical Butler-Volmer kinetics, displaying a fast, heterogeneous electron transfer kinetics, k(0) = 2.27 ± 0.02 cm s(-1), α = 0.4 ± 0.01. Direct reduction of hydrogen peroxide is observed at nanowires across the 110 pM to 1 mM concentration range, without the need for chemical modification, demonstrating the potential of these devices for electrochemical applications.

Reliability assessment of MEMS switches for space applications: laboratory and launch testing

A novel combination of ground-based and flight tests was employed to examine the reliability of capacitive radio-frequency microelectromechanical switches for use in space applications. Laboratory tests were initially conducted to examine the thermomechanical effects of packaging and space-like thermal stresses on the pull-in voltage of the devices; during this process it was observed that operational stability is highly dependent on the geometrical design of the switch and this must be taken in to account during the design stage. To further expose the switches to acceleration levels experienced during a space mission, they were launched on board a sounding rocket and then subjected to free-fall from a height of over 1.3 km with a resulting impact of over 3500g. Post launch analysis indicates that the switches are remarkably resilient to high levels of acceleration. Some evidence is also present to indicate that time-dependent strain relaxation in die attach epoxy materials may contribute to minor variations in device shape and performance.

Integrated magnetics on silicon for power supply in package (PSiP) and power supply on chip (PwrSoC)

The paper introduces the context for the emerging area of integrated power conversion. The key applications driving this trend are outlined and the principal competing technologies are presented encompassing system in package, system on chip and embedded substrate solutions. A system-in-package, 30MHz dc-dc converter using a stacked co-packaging approach is demonstrated. Its enabling key elements, including magnetics on Si technology, a power IC with a digital pulse width modulator and on-chip capacitor, and associated packaging techniques are also presented. A maximum measured efficiency of 71.7% is achieved on the stacked converter with a 30% area reduction compared to side-by-side implementation.

DC/DC converter 3D assembly for autonomous sensor nodes

This paper reports on the design and the manufacturing of an integrated DCDC converter, which respects the specificity of sensor node network: compactness, high efficiency in acquisition and transmission modes, and compatibility with miniature Lithium batteries. A novel integrated circuit (ASIC) has been designed and manufactured to provide regulated Voltage to the sensor node from miniaturized, thin film Lithium batteries. Then, a 3D integration technique has been used to integrate this ASIC in a 3 layers stack with high efficiency passives components, mixing the wafer level technologies from two different research institutions. Electrical results have demonstrated the feasibility of this integrated system and experiments have shown significant improvements in the case of oscillations in regulated voltage. However, stability of this output voltage toward the input voltage has still to be improved.

High frequency DC-DC converter with co-packaged planar inductor and power IC

The paper introduces the trend of integration and miniaturization of power converters with potential for enhanced efficiency, form factor reduction and cost reduction. To demonstrate the concept of highly integrated switched mode power supply with integrated magnetic, a system-in-package DC-DC converter using a stacked co-packaging approach is developed. A system approach was taken to the design, and functional integration, using 3-D packaging for realizing a power supply in package solution (PwrSiP). The target integrated converter is capable of handling an input voltage of 5V and frequencies up to 40MHz. A DC-DC converter IC on a 0.35μm CMOS process was designed to meet this goal. In parallel with the IC design, technology development for on-silicon integrated micro-inductors was completed to achieve small-form factor and extremely low profile. A maximum measured efficiency of 83% and 78% was achieved on the stacked converter operating at 20MHz and 40MHz, respectively. The stacked approach showed a 30% area reduction compared to side-by-side implementation with external discrete inductor.

Dual-Layer Frequency-Selective Grid Polarizers on Thin-Film Substrates for THz Applications

Dual-layer frequency-selective subwavelength grid polarizers on thin-film dielectric substrates are proposed for THz and sub-THz applications. The dual-layer grids possess enhanced (squared) polarizing efficiency at a sequence of discrete frequencies in reflection and within extended frequency bands in transmission as compared to conventional single grids.

Reliability of Plastic-Encapsulated Electronic Components in Supersaturated Steam Environments

Medical steam sterilizers use rapid cycles of temperature, humidity, and pressure to sterilize medical instruments. These cycles represent an exceptionally harsh environment for electronics and, currently, only metal can devices with high-reliability electronic components can be used to electronically monitor and verify the completeness of sterilization. The work presented in this paper has allowed the identification of a material set that allows plastic-encapsulated electronic modules with commercial-off-the-shelf electronic components and sensors, assembled on organic circuit boards, to survive over 100 sterilization cycles. In the course of the work, the failure mechanisms of the plastic-encapsulated modules and the deterioration of encapsulant adhesion over multiple sterilization cycles have been characterized. This opens the possibility of using plastic-encapsulated embedded electronics in smart medical and biomedical devices, which need resterilization after every use.

Thermal Simulation and Characterization of Single Chip Packages

Electronics systems are continuing to strive for higher speeds and reduced size and weight. This results in increased packaging and power density, with a requirement for enhanced thermal performance and more sophisticated techniques for heat removal at the micropackage level. This, in turn, has a significant influence on the interconnection and first level assembly techniques that are used and leads to a requirement for accurate thermal design and validation tools in order to make technology and material choices at the micropackaging and assembly level. Validated thermal modelling tools are proving to be a fast and cost effective method of predicting thermal behaviour and optimising package design to enhance thermal performance. Thus, they can be quickly used to assess different package designs, heat flow strategies, and IC die attach/encapsulation materials without the need to build prototypes.