School of Physics - Research Publications
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ItemControl of Neuronal Survival and Development Using Conductive Diamond(AMER CHEMICAL SOC, 2024-01-17)This study demonstrates the control of neuronal survival and development using nitrogen-doped ultrananocrystalline diamond (N-UNCD). We highlight the role of N-UNCD in regulating neuronal activity via near-infrared illumination, demonstrating the generation of stable photocurrents that enhance neuronal survival and neurite outgrowth and foster a more active, synchronized neuronal network. Whole transcriptome RNA sequencing reveals that diamond substrates improve cellular-substrate interaction by upregulating extracellular matrix and gap junction-related genes. Our findings underscore the potential of conductive diamond as a robust and biocompatible platform for noninvasive and effective neural tissue engineering.
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ItemNo Preview AvailableEffective removal of metal-carbide contamination from diamond circuit boards by reactive ion etching(Elsevier BV, 2023-11-01)
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ItemNo Preview AvailableA Novel Optical Assay System for Bilirubin Concentration Measurement in Whole Blood(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2022-02)As a biomarker for liver disease, bilirubin has been utilized in prognostic scoring systems for cirrhosis. While laboratory-based methods are used to determine bilirubin levels in clinical settings, they do not readily lend themselves to applications outside of hospitals. Consequently, bilirubin monitoring for cirrhotic patients is often performed only intermittently; thus, episodes requiring clinical interventions could be missed. This work investigates the feasibility of measuring bilirubin concentration in whole porcine blood samples using dual-wavelength transmission measurement. A compact and low-cost dual-wavelength transmission measurement setup is developed and optimized to measure whole blood bilirubin concentrations. Using small volumes of whole porcine blood (72 µL), we measured the bilirubin concentration within a range corresponding to healthy individuals and cirrhotic patients (1.2-30 mg/dL). We demonstrate that bilirubin levels can be estimated with a positive correlation (R-square > 0.95) and an accuracy of ±1.7 mg/dL, with higher reliability in cirrhotic bilirubin concentrations (> 4 mg/dL) - critical for high-risk patients. The optical and electronic components utilized are economical and can be readily integrated into a miniature, low-cost, and user-friendly system. This could provide a pathway for point-of-care monitoring of blood bilirubin outside of medical facilities (e.g., patient's home).
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ItemNo Preview AvailablePhotodegradation kinetics for bilirubin sensing: New solutions for old problems(Elsevier BV, 2022-12-01)
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ItemNo Preview AvailableEnhanced effective diffusion in sub-wavelength, axon-scale microchannels using surface acoustic waves(AIP Publishing, 2023-03)Excitation using surface acoustic waves (SAW) has demonstrated efficacy in improving microscale particle/chemical transport due to its ability to generate microscale wavelengths. However, the effects of acoustic stimulation on transport processes along the length of sub-wavelength microchannels and their underlying mechanisms, essential for long-range transport, have not been examined in detail. In this work, we investigate diffusion along the length of subwavelength microchannels using experimental and simulation approaches, demonstrating enhanced transport under SAW excitation. The microchannel-based enhanced diffusion mechanisms are further studied by investigating the acoustic pressure and streaming fields, finding that the degree of enhancement is a function of applied power, microchannel dimensions, and viscosity. This microchannel-based diffusion enhancement approach is applicable to microfluidic and biomedical microscale transport enhancement, with the findings here being relevant to acoustic-based micro-mixing and neurodegenerative therapies.
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Item70 years of bilirubin sensing: towards the point-of-care bilirubin monitoring in cirrhosis and hyperbilirubinemia(ROYAL SOC CHEMISTRY, 2022-09-16)We provide a perspective on monitoring the blood bilirubin concentration using simple methods, which are economical and can be adopted in point of care settings. These are a homecare test system, a miniature implant, and a neonatal wearable patch.
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ItemDiamond Supercapacitors: Towards Durable, Safe, and Biocompatible Aqueous-Based Energy Storage(FRONTIERS MEDIA SA, 2022-05-20)Durable and safe energy storage is required for the next generation of miniature bioelectronic devices, in which aqueous electrolytes are preferred due to the advantages in safety, low cost, and high conductivity. While rechargeable aqueous batteries are among the primary choices with relatively low power requirements, their lifetime is generally limited to a few thousand charging/discharging cycles as the electrode material can degrade due to electrochemical reactions. Electrical double layer capacitors (EDLCs) possess increased cycling stability and power density, although with as-yet lower energy density, due to quick electrical adsorption and desorption of ions without involving chemical reactions. However, in aqueous solution, chemical reactions which cause electrode degradation and produce hazardous species can occur when the voltage is increased beyond its operation window to improve the energy density. Diamond is a durable and biocompatible electrode material for supercapacitors, while at the same time provides a larger voltage window in biological environments. For applications requiring higher energy density, diamond-based pseudocapacitors (PCs) have also been developed, which combine EDLCs with fast electrochemical reactions. Here we inspect the properties of diamond-related materials and discuss their advantages and disadvantages when used as EDLC and PC materials. We argue that further optimization of the diamond surface chemistry and morphology, guided by computational modelling of the interface, can lead to supercapacitors with enhanced performance. We envisage that such diamond-based supercapacitors could be used in a wide range of applications and in particular those requiring high performance in biomedical applications.
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ItemNo Preview AvailableTelecommunication-wavelength two-dimensional photonic crystal cavities in a thin single-crystal diamond membrane(AIP Publishing, 2021-10-25)We demonstrate two-dimensional photonic crystal cavities operating at telecommunication wavelengths in a single-crystal diamond membrane. We use a high-optical-quality and thin (∼300 nm) diamond membrane, supported by a polycrystalline diamond frame, to realize fully suspended two-dimensional photonic crystal cavities with a high theoretical quality factor of ∼8 × 106 and a relatively small mode volume of ∼2(λ/n)3. The cavities are fabricated in the membrane using electron-beam lithography and vertical dry etching. We observe cavity resonances over a wide wavelength range spanning the telecommunication O- and S-bands (1360–1470 nm) with Q factors of up to ∼1800. Our method paves the way for on-chip diamond nanophotonic applications in the telecommunication-wavelength range.
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ItemElectronic Raman scattering as a probe for investigating interactions between impurities in silicon(WILEY, 2019-04)Abstract Electronic Raman scattering (ERS) is investigated as a probe for interactions between impurities in silicon. We report ERS measurements of donors (P, Sb, and As) and acceptors (B) at various concentrations and measurements at various illumination wavelengths. The difference between above and below indirect band gap measurement is discussed in terms of the difficulties of using ERS as a localised probe. We extend the previous literature on impurity interactions of Si:P in the bulk to include Sb and B and demonstrate that the perturbation of the observed ERS transition energy resulting from wavefunction overlap of nearest neighbours is opposite for donors and acceptors. Finally, we model the magnitude of the shift to the first order as a function of the mean impurity atom separation.