Kris Seunarine

Swansea University | SWAN · Department of Computer Science

Internet of Things (IoT) technology is found in many homes. These systems enable tasks to be done more effectively or efficiently-e.g., securing property, monitoring and adjusting resources, tracking behaviours for well-being, and so on. The system presented here was designed with older adults; the vast majority of home IoT systems marketed to this...

As the Internet of Things (IoT) expands, the need for energy-efficient, self-powered devices increases. This study examines light power resource availability for photovoltaics (PV) in various environments and its potential in self-powered IoT applications. We analyse light sources, considering spectral distribution, intensity, and temporal variatio...

The number of interconnected devices, often referred to as the Internet of Things (IoT), is increasing at a considerable rate. It is inevitable therefore that so too will the energy demand. IoT describes a range of technologies such as sensors, software, smart meters, wearable devices, and communication beacons for the purpose of connecting and exc...

With the rapid rise in connectivity in the home, office, and public spaces through the internet of things (IoT), there is a need for an increase in off grid and self-sustainable power solutions for the growing energy requirements of interconnected devices. Here we present an off-grid option for powering a simple IoT device in the home/office. We de...

In this paper, we review and describe how different pho-tovoltaic (PV) materials can be used for designing self-powered interfaces and interactions using indoor ambient light to both power the device and to detect simple shadow-based gestures. We consider seven points when comparing the material technologies: device efficiency, device stability, de...

The interactive, digital future with its seductive vision of Internet-of-Things connected sensors, actuators and displays comes at a high cost in terms of both energy demands and the clutter it brings to the physical world. But what if such devices were made of materials that enabled them to self-power their interactive features? And, what if those...

Method of characterising the surface chemistry of particulate materials, in particular, the surface chemistry of carbon particles, such as graphitic and graphene platelets, and carbon nanotubes.

This paper demonstrates the feasibility of forming multi-functional graphene based surfaces capable of thermal heating for de-icing applications. Developmental ink layers are deposited onto composite laminate skin surfaces and used to melt the ice-skin interface by Joule heating while simultaneously developing a thermal strain in the skin structure...

Thermal energy can be effectively converted into electricity using pyroelectrics, which act as small scale power generator and energy harvesters providing nW to mW of electrical power. In this paper, a novel pyroelectric harvester based on free standing polyvinilidene difluoride (PVDF) was manufactured that exploits the high thermal radiation absor...

Der Fachartikel stellt eine kompakte Zweifarben-Druckanlage für die Fertigung folienbasierter Sensoren aus Graphen vor. Mithilfe einer Graphentinte sowie eines rotativen Tiefdruckverfahrens lassen sich zweidimensionale Elektrodenstrukturen beliebiger Geometrie in hohen Stückzahlen fertigen. Beschrieben werden die Druckanlage, die Herstellung der Ti...

Mesenchymal stem cells are sensitive to changes in feature height, order and spacing. We had previously noted that there was an inverse relationship between osteoinductive potential and feature height on 15-, 55- and 90 nm-high titania nanopillars, with 15 nm-high pillars being the most effective substrate at inducing osteogenesis of human mesenchy...

In this work the direct transfer of nanopatterns into titanium is demonstrated. The nanofeatures are imprinted at room temperature using diamond stamps in a single step. We also show that the imprint properties of the titanium surface can be altered by anodisation yielding a significant reduction in the required imprint force for pattern transfer....

In order to directly imprint features into a hard metal such as titanium, an imprinting stamp composed of material of greater hardness is required. Diamond is the hardest known material, so is an obvious choice for the production of direct-imprint stamps. Diamond also benefits from a low surface energy, chemical inertness, high resistance to wear a...

A simplified transceiver architecture based on resonant tunneling diodes is used to convert phase modulated signals from optical to wireless domain. Conversion of digital and analog modulation is demonstrated at a frequency of 3.2 GHz

A simplified transceiver architecture based on resonant tunneling diodes is used to convert phase modulated signals from optical to wireless domain. Conversion of digital and analog modulation is demonstrated at a frequency of 3.2 GHz.

We present a monolithic passively mode-locked 795nm GaAs/AlGaAs quantum well laser with enlarged vertical mode profile and a low duty-cycle cavity design, emitting 710fs long pulses at a peak power of 9.8W per facet. Semiconductor laser, mode-locked laser, coherent population trapping.

We present an optoelectronic oscillator (OEO) that is capable of generating complex and rich dynamics including stable periodic oscillations and broadband chaos. The OEO under analysis here is based on a resonant tunneling diode (RTD) oscillator driving a laser diode and a time-delayed feedback loop. The RTD based OEO is well described as a a Liena...

We propose and demonstrate a simple and stable low-phase noise optoelectronic oscillator (OEO) that uses a laser diode, an optical fiber delay line, and a resonant tunneling diode (RTD) free-running oscillator that is monolithic integrated with a waveguide photodetector. The RTD-OEO exhibits single-side band phase noise power below -100 dBc/Hz with...

Presently, among the most demanding applications for highly sensitive magnetometers are Magnetocardiography (MCG) and Magnetoencephalography (MEG), where sensitivities of around 1pT.Hz-1/2 and 1fT.Hz-1/2 are required. Cryogenic Superconducting Quantum Interference Devices (SQUIDs) are currently used as the magnetometers. However, there has been som...

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Optoelectronic oscillators can provide low noise oscillators at radio frequencies in the 0.5-40 GHz range and in this paper we review two recently introduced approaches to optoelectronic oscillators. Both approaches use an optical fibre feedback loop. One approach is based on passively modelocked laser diodes and in a 40 GHz oscillator achieves up...

We investigate optoelectronic oscillator (OEO) configurations based on a laser diode driven by resonant tunnelling diode (RTD) optical waveguide photo-detector (PD) oscillators, with an optical fiber feedback loop carrying a fraction of the laser diode optical output that is re-injected into the OEO through the optical waveguide of the RTD-PD. In t...

Recent growing interest in miniature atomic frequency references and precision magnetometers has motivated investigations of coherent population trapping (CPT) and its use in such applications [1]. System designs based on picosecond mode-locked lasers have been previously reported for generating the CPT effect, using Ti:Sapphire lasers passively mo...

We present a low-phase noise microwave oscillator based on a version of an optical fiber optoelectronic oscillator that employs self-injection of a resonant tunneling diode oscillator, integrated with a photo-detector, that drives a laser diode.

A biodegradable substrate with a regular array of nanopillars fabricated by electron-beam lithography and hot embossing is used to address the mechanisms of nanotopographical control of cell behavior. Two different cell lines cultured on the nanopillars show striking differences in cell coverage. These changes are topography- and cell-dependent, an...

In this paper, we report on the influence of shallow micro- and nanopatterned substrata on the attachment and behavior of a human fibroblast [human telomerase transfected immortalized (hTERT)] cells. We identify a hierarchy of textural guidance cues with respect to cell alignment on these substrates. Cells were seeded and cultured for 48 h on silic...

There is a trend towards the production of lithographically defined materials for biological applications. The field of nanobio technology is rapidly growing and so is demand for materials nanostructured in three dimensions. Here we present a hybrid approach where we use electron beam lithography, photolithography and hot embossing to produce membr...

We introduce a novel scaffold fabrication process for making tubular constructs for vascular tissue engineering. Every aspect of the scaffold has been engineered providing unprecedented control of feature size and placement over five orders of magnitude by a combination of electron beam and photolithography. A wide range of micro- and nanotopograph...

A new method for preparing 3D scaffolds for tissue engineering applications with highly controlled micro and nanotopography have been developed. A combination of UV and electron beam lithography was employed for master fabrication and nanoimprint lithography for the preparation of the 3D polymeric scaffolds.

Technology Feature

The occurrence of air-trapping inside poly-eta-caprolactone nanopits was investigated by measuring the contact angles of water droplets on a set of defined nanotopographies. It is shown that the advancing angles follow the Cassie-Baxter theory, thus revealing the presence of air bubbles inside the biodegradable nanopatterns. The importance of these...

The repair of vascular tubing is an important task in tissue engineering. The behavior of cells is strongly influenced by the topology of the surfaces, on both a micrometric and a nanometric scale, in their vicinity. Thus the authors wish to make tubes that are patterned on the inner surface. One way to do this is to use the good depth of focus cap...

This review discusses some of the most common polymer scaffold fabrication techniques used for tissue engineering applications. Although the field of scaffold fabrication is now well established and advancing at a fast rate, more progress remains to be made, especially in engineering small diameter blood vessels and providing scaffolds that can sup...

Bionanotechnology has seen much interest in the past few years. The development in new nanotechnologies and the transfer of such to biomedical applications has been received with large expectations. Here we will describe some of the most common techniques to prepare surfaces with nanometric sized features and how they have been applied to control c...

The application of nanotechnology to biotechnology has increased over the years. One particular area which potentially could benefit from this is cell and tissue engineering. Here we describe various different methods on preparing polymeric substrates and ultimately scaffolds with well-defined micro- and nanometric patterns. Specifically we used el...

While hot embossing of polymers is very attractive for the production of a large number of samples, press techniques can have a longer cycle time for heating and cooling than is desirable. We have addressed this issue by prototyping a new hot embossing press based on optical heating that enables us to reduce the cycle time. In this system the mass...

The article consists of a Powerpoint presentation on nano- and micrometric structures for cell and tissue engineering. The areas discussed include: cell interactive materials; reaction of cells to μm topography; smart μ bandage for tendon; nano-replication by mechanical transfer; low adhesion due to cell mechanics; limits of fibroblast sensing; mes...

The hydrophilicity, hydrophobicity, and sliding behaviour of water droplets on nanoasperities of controlled dimensions were investigated experimentally. We show that the "hemi-wicking"theory for hydrophilic SiO2 samples successfully predicts the experimental advancing angles and that the same patterns, after silanization, become superhydrophobic in...

The hydrophilicity, hydrophobicity, and sliding behavior of water droplets on nanoasperities of controlled dimensions were investigated experimentally. We show that the "hemi-wicking" theory for hydrophilic SiO(2) samples successfully predicts the experimental advancing angles and that the same patterns, after silanization, become superhydrophobic...

The packaging of ferro-electric liquid crystal over silicon (FLCOS) microdisplays presents itself as a formidable challenge to the package designer. The overall assembly should be lightweight, rugged, and incorporate the display engine, the illumination unit and the viewing optics. Good optical performance of the displays depends on many variables...

One of the more critical parts of the fabrication of high quality liquid crystal over silicon (LCOS) devices is a controlled means of introducing the liquid crystal (LC) into the gap formed between the silicon backplane and the coverglass. Existing backplane fabrication techniques leave the mirror elements standing proud of the silicon die, causing...

In this paper we describe the development of a CMOS VLSI backplane for use with micromachined silicon nitride membrane mirrors. The backplane consists of an array of 4096 pixels which are addressed by a 6-bit row decoder. Data enters the chip as a 64-bit logic word at standard CMOS 0-5V levels and is converted to 0-50V at the pixel level by an opti...

Micromachining techniques were developed to meet the demands of microdisplay technology. The micromachining was applied as a post-processing sequence to commercial CMOS wafers. The process development was carried out in response to a strong application requirement coupled with industry need. Micromachining techniques for planarizing optical MEMS we...

Liquid-crystal over silicon is an established technology for reflective spatial light modulators and microdisplays. This paper reviews their development to date, highlighting in particular the micromachining of the mirror array and the associated packaging issues.© (1999) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloadin...

© 1999 Optical Society of America

Liquid crystal over silicon is an established technology for reflective spatial light modulators and microdisplays. In this paper, we describe progress in improving two key performance criteria. The first is backplane flatness; we describe recent developments in the use of chemical mechanical polishing to produce optically flat pixel mirrors on top...

Liquid-crystal over silicon is an established technology for reflective spatial light modulators and microdisplays. This paper reviews their development to date, highlighting in particular the micromachining of the mirror array and the associated packaging issues.

All reflective optical devices fabricated on silicon require flat backplanes. Unfortunately the thermal processing, which is essential in the manufacture of such devices, causes the silicon die to become warped. This backplane warping produces spurious phase modulation effects when the devices are used in coherent applications. Our investigations h...

Post-processing of commercial silicon backplanes have resulted in improved optical performance of liquid crystal (LC) over silicon spatial light modulators (SLMs). The use of chemical mechanical polishing (CMP) to planarise the wafers eliminates the topographical effect of the the underlying circuitry and allows the production of high optical quali...