Robert Groarke

Dublin City University | DCU · Advanced Processing Technology Research Centre (APT)

Owing to the increasing demand for bone repair strategies, several biomaterials have been developed. Among the materials available for this purpose, hydroxyapatite stands out for its osteoinduction capacity, since it possesses a chemical composition similar to that of inorganic bone constituents. In comparison to bones, the mechanical properties of...

This study evaluates the phase and microstructural evolution of additively manufactured (AM) Nickel Titanium (NiTi) alloy, across the interface with 316L stainless steel build plate, in order to understand the processing parameter (input power, layer thickness and scan speed), composition, and microstructure interrelationships necessary to achieve...

Functionally grading material composition in laser-powder bed fusion grants the potential for manufacturing complex components with tailored properties. The challenge in achieving this is that the current laser-powder bed fusion machine technology is designed to process only powdered feedstock materials. This study presents a multi-feedstock materi...

Laser-powder bed fusion was identified as a promising technique for manufacturing metal matrix composites. However, over a decade later, little progress has been made in addressing the persisting issues hindering the wider exploitation and industrial usage of metal matrix composites. Therefore, the present study proposes the implementation of a fea...

Despite the accelerated growth of laser-powder bed fusion in recent years, there are still major obstacles to be overcome before the technology enjoys truly widespread adoption. These include inconsistent part quality and repeatability issues linked to variability in the properties of printed parts. Commonly, the print location across the build pla...

Powder spreading is a crucial step in the powder bed fusion process, which controls the quality of powder bed and consequently affects the quality of printed parts. To date, however, powder spreadability has received very little attention and substantial fundamental work is still needed, largely because of the lack of experimental studies. Therefor...

Laser Powder Bed Fusion (L-PBF) is a technique in which a layer of metal powder is deposited, melted, and solidified using a laser to create a solid layer of metal, with consecutive 2D layers being joined to preceding layers to build up fully solid 3D components. This technique has been the focus of considerable interest from research groups and in...

Laser-Powder Bed Fusion (L-PBF) of metallic parts is a highly multivariate process. An understanding of powder feedstock properties is critical to ensure part quality. In this paper, a detailed examination of two commercial stainless steel 316L powders produced using the gas atomization process is presented. In particular, the effects of the powder...

Laser-powder interaction and meltpool dynamics govern the physics behind the selective laser melting process. Spattering is an unavoidable phenomenon taking place during the process which results in reconstituted particles falling within the powder bed. These are known to influence the interaction between the incident laser beam and the powder. The...

In this work, a gas atomised stainless steel AISI 316L powder was used as metal matrix and SiC was employed as a nano reinforcement. The powders were experimentally characterised to determine the effect of the morphology, size, and levels of reinforcement on the powder flowability. The powder was developed via the powder metallurgy route and the ef...

Nitinol (nickel-titanium or Ni-Ti) is the most utilized shape memory alloy due to its good superelasticity, shape memory effect, low stiffness, damping, biocompatibility, and corrosion resistance. Various material characteristics, such as sensitivity to composition and production thermal gradients, make conventional methods ineffective for the manu...

In this work, pure aluminium powders of different average particle size were compacted, sintered into discs and tested for mechanical strength at different strain rates. The effects of average particle size (15, 19, and 35 μm), sintering rate (5 and 20 °C/min) and sample indentation test speed (0.5, 0.7, and 1.0 mm/min) were examined. A compaction...

As nanotechnology has developed, the creation of nanostructured surfaces has garnered attention for their uses in sensing and catalysis applications. These are however often expensive, time-consuming, and difficult to produce. In contrast, this investigation is focused on the inexpensive, environmentally friendly and fast technique of Confined Atmo...

A novel method for the fabrication of microchannels on cyclic olefin polymer (COP) films is presented. COPs are increasingly popular choices as substrate materials as a result of their promising properties, such as good optical transparency in the near ultraviolet (UV) range, high chemical resistance and low water absorption. This paper presents fa...

Monolithic materials have been investigated as candidates for the efficient separation of chemical and biological species for many years. This article discusses the advances in this area with particular emphasis on poly-methacrylate and silica monoliths, and on the use of these in the separation and enrichment of biomolecules, such as DNA, proteins...

This paper presents a method for fabrication of microchannels on cyclic olefin polymer films that have application in the field of microfluidics and chemical sensing. Continuous microchannels were fabricated on 188-μm-thick cyclic olefin polymer substrates using a picosecond pulsed 1064 nm Nd:YAG laser. The effect of laser fluence on the microchann...

Although less common in analytical environments than their liquid chromatographic counterparts, planar chromatographic techniques such as thin-layer chromatography (TLC) remain widely used. More recently, ultra-thin layer chromatography (UTLC) has become a topic of interest in planar chromatography. The thinner stationary layers (<100 µm) used in U...

Poster Presentation. Winner of the Genzo Shimadzu Award for Best Poster and Flash Presentation.

This review summarizes the development of methacrylate-based polymer monoliths for separation science applications. An introduction to monoliths is presented, followed by the preparation methods and characteristics specific to methacrylate monoliths. Both traditional chemical based syntheses and emerging additive manufacturing methods are presented...

The development of laser-based fabrication techniques for biosensor production

Pulsed laser deposition (PLD) is a mature technique for the growth of thin and ultrathin films whereby stoichiometric transfer of a metal or metal composite target is achieved via laser ablation. When conducted in vacuum or with a low-pressure background gas, thin films can be deposited. Control of plasma density and electron temperature during pul...

Control of plasma density and electron temperature during pulsed laser deposition (PLD) has a large influence over the characteristics of the resultant deposited material [1]. Laser fluence, wavelength, pulse repetition frequency and number of laser shots can be controlled for this purpose [2]. Alternatively, process parameters such as target-to-su...

The synthesis and characterisation of two terpyridine based ruthenium/palladium heteronuclear compounds are presented. The photocatalytic behaviour of the Ru/Pd complex containing the linear 2,2':5',2''-terpyridine bridge () and its analogue the non-linear 2,2':6',2''-terpyridine bridge () are compared together with the respective mononuclear compl...

Novel cyclometallated iridium-Pt/Pd dinuclear complexes containing the bridging ligand 2,2':5',2''-terpyridine (BPP) and the peripheral phenylpyridine (ppy) ligand produced hydrogen under both visible (470 nm) and UV (350 nm) irradiation. The turnover numbers using visible light were found to be significantly higher, indicating an interplay between...

We report on the direct formation of phase pure nanocrystalline cuprous oxide (Cu2O) film with band gap ~ 2 eV by microwave plasma oxidation of pulsed dc magnetron sputtered Cu films and the highly controlled oxidation of Cu in to Cu2O and CuO phases by controlling the plasma exposure time. The structural, morphological and optoelectronic propertie...

A pyrazine bridged ruthenium/palladium bimetallic photocatalyst with peripheral 4,4'-dicarboxyethyl-2,2'-bipyridine ligands, EtOOC-RuPd, is reported, together with its 2,2'-bipyridine analogue. Upon irradiation with visible light, EtOOC-RuPd catalyses the production of hydrogen gas whereas the complex RuPd does not.

The mono- (1) and dinuclear (2) ruthenium(II) bis(2,2'-bipyridine) complexes of 2,5-di(pyridin-2-yl)pyrazine (2,5-dpp), for which the UV/Vis absorption and emission as well as electrochemical properties have been described earlier, are reinvestigated here by resonance, surface enhanced and transient resonance Raman spectroscopy together with select...

The synthesis and characterization of a series of mono- and dinuclear ruthenium(II) and osmium(II) polypyridyl complexes based on the heteroditopic bridging ligand PT are reported. This ligand incorporates bidentate phen (1,10-phenanthroline) and terdentate tpy (2,2':6',2''-terpyridine) units directly connected by their 3 and 5 positions, respectiv...

The complex [(dmcb)(2)Ru(dppz)](PF(6))(2) shows unexpected luminescence in water implying fundamentally different excited state relaxation pathways than are typically observed for complexes of this kind.

The palladium-catalysed cross-coupling reaction between 3,8-dibromo-1,10-phenanthroline with phenylacetylene or 3,5-bis(trifluoromethyl)phenylboronic acid gives good yields of the 3,8-disubstituted products. These 1,10-phenanthroline derivatives are used for the formation of novel ruthenium complexes of the type [(tbbpy)2Ru(phenR2)]2+ [where tbbpy...

This report describes a new route for the fast, economical and effective one-step synthesis and facile workup procedure of 4,4′-dicyano-2,2′-bipyridine (dnbpy) and its corresponding ruthenium complexes. The complex [(tbbpy)2Ru(dnbpy)](PF6)2 was prepared for the first time (tbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine) and the solid-state molecular st...

A heterogeneous system composed of zinc oxide nanorods and ruthenium bipyridyl complex dye molecules is described. The photophysical and spectroscopic properties of the system are reported. It has been found that the ruthenium complex binds well to the zinc oxide nanorods and exhibits strong emission properties characteristic of ruthenium complexes...