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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.

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-square0.95) 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).

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.

Technologies that capture the complex electrical dynamics occurring in biological systems, across fluid membranes and at solid-liquid interfaces drive fundamental understanding and innovation in diverse fields from neuroscience to energy storage. However, the capabilities of existing voltage imaging techniques utilizing micro-electrode arrays, scanning probes, or optical fluorescence methods are respectively limited by resolution, scan speed, and photostability. Here we develop an optoelectronic voltage imaging system which overcomes these limitations by using charge-sensitive fluorescent reporters embedded within a transparent semiconducting diamond device. Electrochemical tuning of the diamond surface termination enables photostable optical voltage imaging with a quantitative linear response at biologically relevant voltages and timescales. This technology represents a major step toward label-free, large-scale, and long-term voltage recording of physical and biological systems with sub-micron resolution.

Surface micro- and nano-patterning techniques are often employed to enhance the optical interface to single photoluminescent emitters in diamond, but the utility of such surface structuring in applications requiring ensembles of emitters is still open to investigation. Here, we demonstrate scalable and fault-tolerant fabrication of closely packed arrays of fluorescent diamond nanopillars, each hosting its own dense, uniformly bright ensemble of near-surface nitrogen-vacancy centers. We explore the optimal sizes for these structures and realize enhanced spin and photoluminescence properties resulting in a 4.5 times increase in optically detected magnetic resonance sensitivity when compared to unpatterned surfaces. Utilizing the increased measurement sensitivity, we image the mechanical stress tensor in each diamond pillar across the arrays and show that the fabrication process has a negligible impact on in-built stress compared to the unpatterned surface. Our results represent a valuable pathway toward future multimodal and vector-resolved imaging studies, for instance in biological contexts.

Innovations in micro- and nanofabrication technologies enable the manufacture of multielectrode arrays for use in neuromodulation and neural recording. Multielectrode arrays make possible medical implants such as pacemakers, deep-brain stimulators, or visual and hearing aids, to treat numerous neural disorders. An optimal neural interface requires a high density of electrodes to precisely record from and stimulate the nervous system while minimizing the overall size of the array. For example, people with retinal degenerative diseases can benefit from retinal prostheses implanted inside the eye. However, at present the visual acuity provided by such implants is well below the threshold for functional vision, mainly due to the limited spatial resolution. In this work, we present a design of 3D nanostructured conductive diamond electrodes, integrated within a polycrystalline diamond housing, offering a high electrode density and count, which simultaneously satisfies spatial resolution and biocompatibility goals. The array is composed of height adjustable pillar electrodes that are 80 μm in diameter and separated by 150 μm. A holistic characterization of the electrodes was performed and the device tested for stimulation performance in a whole-mounted retina. Electrochemical testing showed impedance of 20 kΩ and a wide water window of 2.47 V. The pillar structure allows the distance between the electrodes and the retinal ganglion cells to be reduced which is key to more confined stimulation at lower current levels, leading to potentially higher-acuity stimulation without damaging retinal tissue.

Semiconducting electrodes are increasingly utilised for neural interfacing applications, such as neural recording, stimulation, and photomodulation. To characterize the performance of these electrodes, photoelectrochemical analysis is often undertaken in biologically relevant electrolytes. These include electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and for photomodulation applications, photocurrent (PC) measurements. From such measurements, it is possible to deduce key properties of semiconductor surfaces, such as electrochemical impedance and capacitance, as well as mechanisms of charge transfer. To extract these parameters from the experimental data, equivalent electrical circuit modelling is often employed, but usually only for a single technique at a time which often misses key insights about the processes occurring at the electrode-electrolyte interface. Here we present an equivalent circuit model that simultaneously describes the results from CV, EIS, and PC transient measurements. Using semiconducting nitrogen-doped ultrananocrystalline diamond (N-UNCD) electrodes in saline solution, we show that the model describes physical mechanisms that occur at the interface with electrolyte, encompassing the space charge region, the electrical double layer, and the electrolyte. Using the model we are able to optimize parameters relevant for neural interfacing and suggest that this framework may assist in the characterization of other semiconducting electrodes.

Stents are a common biomedical device used to treat atherosclerosis, but they are typically passive and employ no electronics. This article details the design, fabrication, and testing of a miniaturized circuit board capable of telemetry via a stent antenna. The circuit is less than 1.1 mm in diameter making it sufficiently miniaturized to be delivered via a catheter. Experiments in porcine tissue achieved a data rate of 277 kb/s with a 280-MHz carrier. The implant was tested at depths of 3, 6, and 9 mm, requiring a transmitter power of 44, 48, and 63 mW, respectively, to operate, surpassing specifications reported in previous electronic stent-based works. These measurements confirm that stents incorporating a power and data link could be used to monitor biological indicators such as blood pressure, blood glucose, or even neural signals.

Vision impairment caused by degenerative retinal pathologies such as age-related macular degeneration can be treated using retinal implants. Such devices receive power and data using cables passing through a permanent surgical incision in the eye wall (sclera), which increases the risk to patients and surgical costs. A recently developed retinal implant design eliminates the necessity of the implant cable using a photonic power converter (PPC), which receives optical power and data through the pupil and is directed by an ellipsoidal reflector and micro-electromechanical mirror. We present a misalignment compensation algorithm model that accounts for rigid-body motions of the reflector relative to the eye and applies the correction to the mirror coordinates in the presence of angular misalignment of the reflector. We demonstrate that up to 85% of the nominal optical power can be delivered to the implant with axial reflector misalignments up to 30 deg using the compensation algorithm.

The study of neurons is fundamental for basic neuroscience research and treatment of neurological disorders. In recent years ultrasound has been increasingly recognized as a viable method to stimulate neurons. However, traditional ultrasound transducers are limited in the scope of their application by self-heating effects, limited frequency range and cavitation effects during neuromodulation. In contrast, surface acoustic wave (SAW) devices, which are producing wavemodes with increasing application in biomedical devices, generate less self-heating, are smaller and create less cavitation. SAW devices thus have the potential to address some of the drawbacks of traditional ultrasound transducers and could be implemented as miniaturized wearable or implantable devices. In this mini review, we discuss the potential mechanisms of SAW-based neuromodulation, including mechanical displacement, electromagnetic fields, thermal effects, and acoustic streaming. We also review the application of SAW actuation for neuronal stimulation, including growth and neuromodulation. Finally, we propose future directions for SAW-based neuromodulation.

Polyaromatic hydrocarbons (PAHs), such as pyrene, benzo[a]pyrene, phenanthrene, and anthracene induce toxic, carcinogenic, and mutagenic effects on living organisms and are considered as primary pollutants. Traditional methods for their identification are often laborious and time-consuming and do not account for the heterogeneous nature of their distribution. Here we present confocal microscopy as a rapid and accurate technique for direct analysis of PAHs in soil samples without the complexity of sample pre-processing which might delay results for several days. The method uses the intrinsic fluorescence of PAHs for detection and their emission spectra for the identification of different PAHs. A clear difference was observed in the fluorescence spectral properties of phenanthrene, pyrene and naphthalene in real-time environmental samples. The post-processing of confocal scans obtained in the detection stage of PAHs was completed through the application of ImageJ software. Intrinsic fluorescence-based detections of PAHs may open new avenues in terms of rapid detection and identification of PAHs in heterogeneous complex soil samples.

The performance of many implantable neural stimulation devices is degraded due to the loss of neurons around the electrodes by the body's natural biological responses to a foreign material. Coating of electrodes with biomolecules such as extracellular matrix proteins is one potential route to suppress the adverse responses that lead to loss of implant functionality. Concurrently, however, the electrochemical performance of the stimulating electrode must remain optimal to continue to safely provide sufficient charge for neural stimulation. We have previously found that oxygen plasma treated nitrogen included ultrananocrystalline diamond coated platinum electrodes exhibit superior charge injection capacity and electrochemical stability for neural stimulation (Sikder et al., 2019). To fabricate bioactive diamond electrodes, in this work, laminin, an extracellular matrix protein known to be involved in inter-neuron adhesion and recognition, was used as an example biomolecule. Here, laminin was covalently coupled to diamond electrodes. Electrochemical analysis found that the covalently coupled films were robust and resulted in minimal change to the charge injection capacity of diamond electrodes. The successful binding of laminin and its biological activity was further confirmed using primary rat cortical neuron cultures, and the coated electrodes showed enhanced cell attachment densities and neurite outgrowth. The method proposed in this work is versatile and adaptable to many other biomolecules for producing bioactive diamond electrodes, which are expected to show reduced the inflammatory responses in vivo.

We operate a fiberbased cavity with an inserted diamond membrane containing ensembles of silicon vacancy centers (SiV$^-$) at cryogenic temperatures $ \geq4~$K. The setup, sample fabrication and spectroscopic characterization is described, together with a demonstration of the cavity influence by the Purcell effect. This paves the way towards solid state qubits coupled to optical interfaces as long-lived quantum memories., 10 pages, 6 figures

State of the art bioelectronic implants are using thin cables for therapeutic electrical stimulation. If cable insulation is thin, biological tissue surrounding cables can be unintentionally stimulated. The capacitance of the cable must be much less than the stimulating electrodes to ensure stimulating currents are delivered to the electrode-tissue interface. This work derives and experimentally validates a model to determine the capacitance of parallel cables implanted in biological tissue. Biological tissue has a high relative permittivity, so the capacitance of cabling implanted in the human body depends on cable insulation thickness. Simulations and measurements demonstrate that insulation thickness influences the capacitance of implanted parallel cables across almost two orders of magnitude: from 20 pF/m to 700 pF/m. The results are verified using four different methods: solving the Laplacian numerically from first principles, using a commercially available electrostatic solver, and measuring twelve different parallel pairs of wires using two different potentiostats. Cable capacitance simulations and measurements are performed in air, a porcine blood pool and porcine muscle tissue. The results do not differ by more than 30% for a given cable across simulation and measurement methodologies. The modelling in this work can be used to design cabling for minimally-invasive biomedical implants.

Cesium dihydrogen phosphate CsH2PO4 (CDP) is a ferroelectric with ordering temperature Tc = 154 K. In many respects CDP is a unique material, displaying a chain and layer-like structure and a pseudo-one-dimensional ordering of the hydrogen ions at Tc, making it an attractive candidate for the application of a pseudo-one-dimensional Ising model.The elastic constants of a material completely describe itselastic behaviour. As a first step in the understanding of the lattice dynamics of CDP, the room temperature elastic constants have been determined using ultrasonic velocity measurements. The constants have been used to calculate a number of elastic properties: the phase and group velocities, Young's modulus, the bulk modulus, linear compressibilities, and the elastic Debye temperature. The calculations showed a marked elastic anisotropy which has been correlated with the chain and layer-like structure of this material. The one-dimensional nature of the ordering of the hydrogen ions can be expected to be evident in a wide range of critical phenomena. In an attempt to elucidate further the transition mechanism of CDP, the temperature dependences of the velocity and attenuation, thermal expansion, and dielectric constant were measured in the critical region. The critical point analyses of the dielectric and ultrasonic anomalies showed evidence of a temperature region above Tc in which one-dimensional, short-range forces were dominant. However, very close to Tc, the usual 3-D, long-range, dipole-dipole interaction was found to be dominant. Calculations of the Grilneisen parameters based on the expansion measurements have revealed that, from the thermodynamic point of view, the degree of "one-dimensionality" of CDP increases as the transition is approached. However, despite the one-dimensional nature of the transition, a significant anomaly was observed in the dielectric constant measured orthogonal to the ferroelectric axis. Whilst most of the analysis of this study was for T > Tc, a very long term relaxation effect in the dielectric constant was observed below Tc , which suggested that CDP has a very "soft" domain structure in the ferroelectric state. Several suggestions are made as to possible further investigations into these domain effects. The findings of this study constitute one more step in the overall understanding of the lattice dynamics of CDP. Directions for future research based on these findings are also presented.

We present a study of the structural and electronic properties of ultra-nanocrystalline diamond films that were modified by adding nitrogen to the gas mixture during chemical vapour deposition growth. Hall bar devices were fabricated from the resulting films to investigate their electrical conduction as a function of both temperature and magnetic field. Through low-temperature magnetoresistance measurements, we present strong evidence that the dominant conduction mechanism in these films can be explained by a combination of 3D weak localization (3DWL) and thermally activated hopping at higher temperatures. An anisotropic 3DWL model is then applied to extract the phase-coherence time as function of temperature, which shows evidence of a power law dependence in good agreement with theory., Comment: 13 pages, 10 figures

The proliferation of digital data and internet-based research technologies is transforming the research landscape, and researchers and research ethics communities are struggling to respond to the ethical issues being raised. This paper discusses the findings from a collaborative project that explored emerging ethical issues associated with the expanding use of digital data for research. The project involved consulting with researchers from a broad range of disciplinary fields. These discussions identified five key sets of issues and informed the development of guidelines orientated to meet the needs of researchers and ethics committee members. We argue that establishing common approaches to assessing ethical risks of research involving digital data will promote consistency in the ethical standards for research, enable the smooth functioning of ethics committees, and sustain public confidence in research. We conclude with recommendations for the development of educational resources for ethics committees, data management guidelines and further public education.

Polycyclic aromatic hydrocarbons (PAHs) are recalcitrant pollutants that can induce carcinogenic, hazardous and mutagenic effects in living organisms. Numerous traditional methods are available for their identification, but these methods require large samples and are time-consuming. In this study we have developed a new method for the determination of PAHs by exploiting their intrinsic fluorescence characteristics. The aim of this research is to investigate real time identification of different PAHs including; Naphthalene, Pyrene and Phenanthrene by using their autofluorescence properties. These pollutants have shown specific optical signatures that are useful for their rapid detection in the contaminated area. In addition to their specific emission spectra, lifetime analysis also can be used to distinguish PAHs with high level of certainty. Our research offers new avenues for real time detection of pollutants.

Nematode eggs are pervasive pathogens that infect billions of people and livestock every year. Adult parasitic nematode worms can be distinguished based on their size and morphology. However, their eggs, particularly their species Ascaris lumbricoides and Ascaris suum cannot be identified from each other. Identifying eggs of helminths from wastewater and sludge is important from a public health perspective to minimize the spread of Ascaris infections. Numerous methods exist for nematode identification, from a morphological-based approach to high throughput sequencing technology. However, these techniques are not consistent and often laborious and time-consuming. In this study, we demonstrate that non-invasive real-time identification of eggs is possible based on their intrinsic fluorescence. Using confocal microscopy, we investigate the autofluorescence properties of five species of nematode eggs and observe clear differences between genus and for the first time their species in sludge samples. This non-invasive imaging technique could lead to better understanding of these species and may assist in early control of diseases.

Optogenetic neuromodulation is a powerful technique used to study cells that form part of neuronal circuits. Light stimulation of neurons has led to a deeper understanding of autism, schizophrenia and depression. However, researchers are often limited to tethered systems involving percutaneous plugs, hence, wireless power transmission to an implantable device is desirable. This work details the design, fabrication and testing of multichannel wirelessly powered optogenetic devices. By employing several carefully tuned resonant tank circuits, this work demonstrates the ability to address a scalable number of light sources on a single device. Single channel, dual channel and 16 channel devices were fabricated, achieving light output readings of up to 15mW at 473nm, suitable for activating channelrhodopsin. Wireless power transmission was characterized in air and porcine tissue for implant depths up to 30mm, making device implantation feasible. The device was successful in activating endogenous (in retinal ganglion cells) and exogenously transfected channelrhodopsin in human embryonic kidney cells, providing biological validation. The significance of this approach is the removal of power-hungry and area-consuming electronics from the implant, while the ability to address and modulate individual light sources is maintained by shifting this complexity to the external wireless power transmitter.

Plasma catalysis has drawn attention from the plasma and chemical engineering communities in the past few decades as a possible alternative to the long-established Haber–Bosch process for ammonia production. The highly reactive electrons, ions, atoms, and radicals in the plasma significantly enhance the chemical kinetics, allowing ammonia to be produced at room temperature and atmospheric pressure. However, despite the promise of plasma catalysis, its performance is still well short of that of the Haber–Bosch process. This is at least in part due to the lack of understanding of the complex mechanisms underlying the plasma–catalyst interactions. Gaining such an understanding is a prerequisite for exploiting the potential of plasma catalysis for ammonia production. In this perspective, we discuss possible benefits and synergies of the combination of plasma and catalyst. The different regimes of plasma discharges and plasma reactor configurations are introduced and their characteristics in ammonia synthesis ...

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 ~ $8\times10^6$ and a relatively small mode volume of ~2$({\lambda}/n)^3$. 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 nm-1470 nm) with Q factors of up to ~1800. Our method offers a new direction for on-chip diamond nanophotonic applications in the telecommunication-wavelength range.

Nanotechnology has engraved new insight into the material sciences and zinc oxide nanomaterials (ZnO NMs) are one of the most extensively used materials in healthcare and environmental remediation applications attributable to their biodegradability and tunable physical and chemical properties. This review concentrates on three aspects of ZnO NMs. Firstly, we review green methods of the synthesis of ZnO NMs as an alternative to conventional synthesis routes as the latter pose environmental risks such as the requirement of hazardous and expensive precursors as well as production of unwanted end products. Also, green methods can produce important and diversified morphologies. Secondly, ZnO NMs are ubiquitous in numerous biological fields and other consumer products which motivate us to review advances in assessing their toxicological effects via in-vitro and in-vivo studies. Thirdly, an emerging application space for ZnO NMs is bioimaging, biosensing and traceable drug delivery which take advantage of their unique variable optical properties and in particular, their fluorescent behavior. The inhibitory action of these NMs against microbes, cancer and inflammation is also covered. The aim is to provide critical review on perspectives and challenges associated with fluorescent-based nascent applications that can be utilized for targeting, detecting and treating severe human ailments.

Ion irradiation is a widely employed tool to fabricate diamond micro- and nano-structures for applications in integrated photonics and quantum optics. In this context, it is essential to accurately assess the effect of ion-induced damage on the variation of the refractive index of the material, both to control the side effects in the fabrication process and possibly finely tune such variations. Several partially contradictory accounts have been provided on the effect of the ion irradiation on the refractive index of single crystal diamond. These discrepancies may be attributable to the fact that in all cases the ions are implanted in the bulk of the material, thus inducing a series of concurrent effects (volume expansion, stress, doping, etc.). Here we report the systematic characterization of the refractive index variations occurring in a 38 µm thin artificial diamond sample upon irradiation with high-energy (3 MeV and 5 MeV) protons. In this configuration the ions are fully transmitted through the sample, while inducing an almost uniform damage profile with depth. Therefore, our findings conclusively identify and accurately quantify the change in the material polarizability as a function of ion beam damage as the primary cause for the modification of its refractive index.

This paper proposes a vibration model of ions as an improvement over the conventional Gouy–Chapman–Stern theory, which is used to model the electrical double layer capacitance and to study the ionic dynamics at electrode/electrolyte interfaces. Although the Gouy–Chapman–Stern model is successful for small applied potentials, it fails to explain the observed behavior at larger potentials, which are becoming increasingly important as materials with high charge injection capacities are developed. A time-dependent study on ionic transport indicates that ions vibrate near the electrode surface in response to the applied electric field. This vibration allows us to correctly predict the experimentally observed decreasing differential capacitance at high electrode potential. This new model elucidates the mechanism behind the ionic dynamics at solid–electrolyte interfaces, providing useful insight that may be applied to many electrochemical systems in energy storage, photoelectrochemical cells, and biosensing.

Objective With the strong drive towards miniaturization of active implantable medical devices and the need to improve the resolution of neural stimulation arrays, there is keen interest in the manufacture of small electrodes capable of safe, continuous stimulation. Traditional materials such as platinum do not possess the necessary electrochemical properties to stimulate neurons safely when electrodes are very small (i.e. typically less than about 300 µm (78 400 µm2)). While there are several commercially viable alternative electrode materials such as titanium nitride and iridium oxide, an attractive approach is modification of existing Pt arrays via a high electrochemical capacitance material coating. Such a composite electrode could still take advantage of the wide range of fabrication techniques used to make platinum-based devices. The coating, however, must be biocompatible, exhibit good adhesion and ideally be long lasting when implanted in the body. Approach Platinum foils were roughened to various degrees with regular arrays of laser milled pits. Conducting diamond films were grown on the foils by microwave plasma chemical vapor deposition. The adhesion strength of the films to the platinum was assessed by prolonged sonication and accelerated aging. Electrochemical properties were evaluated and compared to previous work. Main results In line with previous results, diamond coatings increased the charge injection capacity of the platinum foil by more than 300% after functionalization within an oxygen plasma. Roughening of the underlying platinum substrate by laser milling was required to generate strong adhesion between the diamond and the Pt foil. Electrical stress testing, near the limits of safe operation, showed that the diamond films were more electrochemically stable than platinum controls. Significance The article describes a new method to protect platinum electrodes from degradation in vivo. A 300% increase in charge injection means that device designers can safely employ diamond coated platinum stimulation electrodes at much smaller sizes and greater density than is possible for platinum.

Retinal prostheses have the potential to restore vision to blind patients that have retinitis pigmentosa or similar hereditary degenerative disorders, by electrically stimulating surviving retinal neurons through implanted electrode arrays. Current retinal prostheses provide limited visual acuity and one challenge is to spatially control neural activation following electrical stimulation. Most of the retinal prostheses are either epi-retinal - in front of the retinal ganglion cell layer, or sub-retinal - behind photoreceptor layer. In this study, we performed calcium imaging of ganglion cells from whole mounted retinas and compared the spread of neural activation between epi-retinal stimulation with a fiber electrode and sub-retinal stimulation with a disk electrode. We investigated the effects of phase durations on the spatial resolution of biphasic stimulation. Our results suggest that with fiber electrode epi-retinal stimulation, the axon bundles activation can lead to significant spread of stimulation, and cannot be avoided simply by changing the phase durations. However, sub-retinal stimulation with very short pulses (phase duration 0.033ms) can effectively confine the activation of retinal ganglion cells.

A laser-based power and data delivery scheme is described for completely wireless operation of a epiretinal prostheses. Laser steering is achieved using a single, two-axis microelectromechanical system mirror and a custom curved reflection optic are used to enable beam trajectories at different angular coordinates of the pupil. Real-time pupil detection and laser steering operation are characterized on a 3D printed robotic eye platform and optimized for maximum optical power delivery., 2019 Photonics North (PN), May 21-23, 2019, Quebec City, QC, Canada

The electrochemical capacitance of nitrogen-doped ultrananocrystalline diamond (N-UNCD) can be dramatically increased by treating the surface with an RF-oxygen plasma. Such treated surfaces display excellent properties for use as electrodes in neural stimulation and recording. In the present work, we elucidate the origins of this phenomenon by investigating the effects of different methods of oxygen termination. We found that the increase in electrochemical capacitance is dependent on the details of the method used for oxygen termination. Whilst N-UNCD subjected to UV/ozone treatment, oxygen plasma treatment, and furnace annealing in oxygen gas all displayed increased surface capacitance, the highest capacitance was exhibited by the oxygen annealed sample, with which we achieved ~ 3 orders of magnitude increase in the electrochemical capacitance as compared to the as-grown sample. The maximum recorded capacitance was 3746 ± 132 µF cm−2, which is substantially greater than previously reported N-UNCD electrodes’ electrochemical capacitance (1070 µF cm−2, W. Tong. et al, 2016). Our findings point to the presence of sub-surface solid state capacitance which contributes significantly to the observed electrochemical capacitance of the oxygen terminated N-UNCD electrodes. When combined with the favourable biocompatibility and inertness of the N-UNCD, our approach may provide a route towards the development of advanced neural sensing and stimulating electrodes.

Prototype electronic devices have been critical to the discovery and demonstration of the unique properties of new materials, including composites based on carbon nanotubes (CNT) and graphene. However, these devices are not typically constructed with durability or biocompatibility in mind, relying on conductive polymeric adhesives, mechanical clamps or crimps, or solders for electrical connections. In this paper, two key metallization techniques are presented that employ commercially-available brazing alloys to fabricate electronic devices based on diamond and carbonaceous wires. Investigation of the carbon—alloy interfacial interactions was utilized to guide device fabrication. The interplay of both chemical (“adhesive”) and mechanical (“cohesive”) forces at the interface of different forms of carbon was exploited to fabricate either freestanding or substrate-fixed carbonaceous electronic devices. Elemental analysis in conjunction with scanning electron microscopy of the carbon—alloy interface revealed the chemical nature of the Ag alloy bond and the mechanical nature of the Au alloy bond. Electrical characterization revealed the non-rectifying nature of the carbon—Au alloy interconnects. Finally, electronic devices were fabricated, including a Au circuit structure embedded in a polycrystalline diamond substrate.

We investigate the synthesis of ammonia in a non-equilibrium atmospheric-pressure plasma using functionalized-nanodiamond and diamond-like-carbon coatings on α-Al2O3 spheres as catalysts. Oxygenated nanodiamonds were found to increase the production yield of ammonia, while hydrogenated nanodiamonds decreased the yield. Neither type of nanodiamond affected the plasma properties significantly. Using diffuse-reflectance FT-IR and XPS, the role of different functional groups on the catalyst surface was investigated. Evidence is presented that the carbonyl group is associated with an efficient surface adsorption and desorption of hydrogen in ammonia synthesis on the surface of the nanodiamonds, and an increased production of ammonia. Conformal diamond-like-carbon coatings, deposited by plasma-enhanced chemical vapour deposition, led to a plasma with a higher electron density, and increased the production of ammonia.