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 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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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 AvailableMiniature power and data transceiver based on multimodal operation of a single photovoltaic device(IOP Publishing, 2020)Wireless bi-directional data telemetry and power delivery are demonstrated using a single photovoltaic (PV) cell. The same cell functions as a light-emitting diode (LED), a power transducer, and a reverse-biased photodiode. This is achieved through the use of a simple inductor-capacitor resonator, with the cell’s junction providing the circuit’s capacitive element. We show that pulsed illumination at the circuit’s resonance frequency results in active switching of the PV cell between the three operating modes. Using this approach we demonstrate backward data transmission in the form of optical pulses generated by the PV cell, as well as enhanced forward data transmission and power generation. This work demonstrates the principle of using a single PV cell as an optical data transceiver while simultaneously generating energy using only two circuit elements; an inductor and a PV cell. This approach benefits miniature wireless devices, such as medical implants, which operate within significant size, weight, and energy constraints.
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ItemFeasibility of Nitrogen Doped Ultrananocrystalline Diamond Microelectrodes for Electrophysiological Recording From Neural Tissue(FRONTIERS MEDIA SA, 2018-06-22)Neural prostheses that can monitor the physiological state of a subject are becoming clinically viable through improvements in the capacity to record from neural tissue. However, a significant limitation of current devices is that it is difficult to fabricate electrode arrays that have both high channel counts and the appropriate electrical properties required for neural recordings. In earlier work, we demonstrated nitrogen doped ultrananocrystalline diamond (N-UNCD) can provide efficacious electrical stimulation of neural tissue, with high charge injection capacity, surface stability and biocompatibility. In this work, we expand on this functionality to show that N-UNCD electrodes can also record from neural tissue owing to its low electrochemical impedance. We show that N-UNCD electrodes are highly flexible in their application, with successful recordings of action potentials from single neurons in an in vitro retina preparation, as well as local field potential responses from in vivo visual cortex tissue. Key properties of N-UNCD films, combined with scalability of electrode array fabrication with custom sizes for recording or stimulation along with integration through vertical interconnects to silicon based integrated circuits, may in future form the basis for the fabrication of versatile closed-loop neural prostheses that can both record and stimulate.