Patrick Degenaar

Newcastle University | NCL · School of Electrical and Electronic Engineering

Optogenetic-based neuroprosthetic therapies are increasingly being considered for human trials. However, the optoelectronic design of clinical-grade optogenetic-based neuroprosthetic probes still requires some thought. Design constraints include light penetration into the brain, stimulation efficacy, and probe/tissue heating. Optimisation can be ac...

Electrical neurostimulation has been used successfully as a technique in both research and clinical contexts for over a century. Despite significant progress, inherent problems remain, hence there has been a drive for novel neurostimulation modalities including ultrasonic, magnetic, and optical, which have the potential to be less invasive, have en...

Neuromodulation is an established treatment for numerous neurological conditions, but to expand the therapeutic scope there is a need to improve the spatial, temporal and cell-type specificity of stimulation. Optogenetics is a promising area of current research, enabling optical stimulation of genetically-defined cell types without interfering with...

Modern Active Medical Implantable Devices require communications to transmit information to the outside world or other implantable sub-systems. This can include physiological data, diagnostics, and parameters to optimise the therapeutic protocol. The available options are to use optical, radiofrequency, or ultrasonic communications. However, in all...

The recent development of optogenetic tools, to manipulate neuronal activity using light, provides opportunities for novel brain-machine interface (BMI) control systems for treating neurological conditions. An issue of critical importance, therefore, is how well light penetrates through brain tissue. We took two different approaches to estimate lig...

Memristors are used in many innovative research areas. However, the temperature has a strong effect on memristance, which results in malfunctions. Although commercial a memristor is available, its thermal characteristics are still under-explored. This paper presents a temperature model of a self-directed channel memristor. The experimental results...

Electrical neurostimulation is effective in treating neurological disorders, but associated recording artefacts generally limit applications to ‘open-loop’ stimuli. Since light does not prevent concurrent electrical recordings, optogenetics enables real-time, continuous ‘closed-loop’ control of brain activity. Here we show that closed-loop optogene...

Objective: This work described a video information processing scheme for optogenetic forms of visual cortical prosthetics. Approach: The architecture is designed to perform a processing sequence: Initially simplifying the scene, followed by a pragmatic visual encoding scheme which assumes that initially optical stimulation will be stimulating bu...

Brain-machine Interfaces (BMI) hold great potential for treating neurological disorders such as epilepsy. Technological progress is allowing for a shift from open-loop, pacemaker-class, intervention towards fully closed-loop neural control systems. Low power programmable processing systems are therefore required which can operate within the thermal...

This paper introduces a new hybrid microfabrication technique which combines ultra-precision micro-milling and a ductile sacrificial material deposition process to fabricate a silicon-based implant for neuroprosthetics applications with near defect-free quality at several hundreds of micrometres in thickness. The sacrificial materials can influence...

Object recognition is a challenging problem in high-level vision. Models that perform well for the outdoor domain, perform poorly in the indoor domain and the reverse is also true. This is due to the dramatic discrepancies of the global properties of each environment, for instance, backgrounds and lighting conditions. Here, we show that inferring t...

The coming years may see the advent of distributed implantable devices to support bioelectronic medicinal treatments. Communication between implantable components and between deep implants and the outside world can be challenging. Percutaneous wired connectivity is undesirable and both radiofrequency and optical methods are limited by tissue absorp...

Background: It is widely accepted by the scientific community that bioelectrical signals, which can be used for the identification of neurophysiological biomarkers indicative of a diseased or pathological state, could direct patient treatment towards more effective therapeutic strategies. However, the design and realisation of an instrument that c...

Background: One of the major concerns in implantable optoelectronics is the heat generated by emitters such as light emitting diodes (LEDs). Such devices typically produce more heat than light, whereas medical regulations state that the surface temperature change of medical implants must stay below + 2 °C. The LED's reverse current can be employed...

We develop a system-level approach to modelling optogenetic-neurons firing behaviour in in-vivo conditions. This approach contains three sub-modules: 1) a Mie/Rayleigh scattering mode of light penetration in tissue; 2) a classic likelihood Poisson spiking train model; 3) a 4-state model of the Channelrhodopsin-2 (ChR2) channel added to a CA3 neuron...

This paper presents a design and implementation of an ultrasonic wireless communication link for an injectable biomedical implanted device. The results address how the ultrasound link encounter from the multiple paths propagation effect. The ultrasound link characterized in term of channel impulse response and power transmission losses against the...

This paper proposes design considerations that need to be followed in order to eliminate potential sources of artefact that could distort a recorded neural signal. The artefact that appears in a recorded signal has a combination of potential sources each of which contributes towards its formation. As such, these sources of artefact have been addres...

Optogenetics is a fast growing neuromodulation techniques as it can remotely stimulate neural activities of a genetically modified cells. The advantage of remotely controlling the neural activity triggered researchers to implement a headset to externally stimulate retina cells for people with retina pigmentosa. The wearable device requires an effic...

Objective: Recording of local field potentials (LFPs) during deep brain stimulation (DBS) is necessary to investigate the instantaneous brain response to stimulation, minimize time delays for closed-loop neurostimulation and maximise the available neural data. To our knowledge, existing recording systems lack the ability to provide artefact-free h...

Direct patterning of functional microstructures on monocrystalline silicon by mechanical micro milling has drawn intense interests as an alternative to the conventional lithography techniques in microelectronics fabrication. Despite mechanical micro milling offering advantages such as high versatility and low operating cost, machining-induced defec...

Excessive generation of undesirable surface and subsurface damages such as surface edge chipping often occurs when monocrystalline silicon, a hard and brittle material, is machined at tens to hundreds of microns in thickness. However, before developing strategies to reduce edge chipping and improve the machining efficiency by micro-milling, underst...

Objective: Our main objective is to demonstrate that compact high radiance gallium nitride displays can be used with conventional virtual reality optics to stimulate an optogenetic retina. Hence, we aim to introduce a non-invasive approach to restore vision for people with conditions such as retinitis pigmentosa where there is a remaining viable c...

Neuromodulation technologies are progressing from pacemaking and sensory operations to full closed-loop control. In particular, optogenetics—the genetic modification of light sensitivity into neural tissue allows for simultaneous optical stimulation and electronic recording. This paper presents a neural interface application-specified integrated ci...

Retinal prosthesis is steadily improving as a clinical treatment for blindness caused by retinitis pigmentosa. However, despite the continued exciting progress, the level of visual return is still very poor. It is also unlikely that those utilising these devices will stop being legally blind in the near future. Therefore, it is important to develop...

Implantable photonic probes are of increasing interest to the field of biophotonics and in particular, optogenetic neural stimulation. Active probes with onboard light emissive elements allow for electronic multiplexing and can be manufactured through existing microelectronics methods. However, as the optogenetics field moves towards clinical pract...

There is a growing demand for the development of new types of implantable optoelectronics to support both basic neuroscience and optogenetic treatments for neurological disorders. Target specification requirements include multi-site optical stimulation, programmable radiance profile, safe operation, and miniaturization. It is also preferable to hav...

Objective: This work presents a method to determine the surface temperature of microphotonic medical implants like LEDs. Our inventive step is to use the photonic emitter (LED) employed in an implantable device as its own sensor and develop readout circuitry to accurately determine the surface temperature of the device. Approach: There are two p...

Optogenetics is a technique to genetically photosensitize neural tissue for both sensing and stimulus. Since its discovery in 2003, it has led to numerous scientific discoveries in basic neuroscience. Now, various groups are attempting to utilise the technique for neuroprosthetic therapies. This chapter explores the background of the technique and...

In this paper, we demonstrate that a low power flash FPGA based micro-system can provide a low power programmable interface for closed-loop brain implant inter- faces. The proposed micro-system receives recording local field potential (LFP) signals from an implanted probe, performs closed-loop control using a first order control system, then conver...

Objective: Computer vision-based assistive technology solutions can revolutionise the quality of care for people with sensorimotor disorders. The goal of this work was to enable trans-radial amputees to use a simple, yet efficient, computer vision system to grasp and move common household objects with a two-channel myoelectric prosthetic hand. Ap...

Optical neuron stimulation arrays are important for both in-vitro biology and retinal prosthetic biomedical applications. Hence, in this work, we present an 8100 pixel high radiance photonic stimulator. The chip module vertically combines custom made gallium nitride $\mu$ LEDs with a CMOS application specific integrated circuit. This is designed wi...

Visual processing has attracted a lot of attention in the last decade. Hierarchical approaches for object recognition are gradually becoming widely-accepted. Generally, they are inspired by the ventral stream of human visual cortex, which is in charge of rapid categorization. Similar to objects, natural scenes share common features and can, therefo...

This paper proposes a self-diagnostic subsystem for a new generation of brain implants with active electronics. The primary objective of such probes is to deliver optical pulses to optogenetic tissue and record the subsequent activity, but lifetime is currently unknown. Our proposed circuits aim to increase the safety of implanting active electroni...

Optogenetics is a gene-therapy technique which utilizes high radiance light to stimulate the genetically modified nerve cells. An optical delivery method in brain tissue for optogenetics can be performed using incorporated micro-LEDs. Optrode lifespan can be affected by the electrodes degradation caused by the generated charges over the tissue afte...

Optogenetics, a gene therapy technique for photosensitizing nerve tissue, is rapidly moving from the scientific domain towards clinical practice. The first human application of this technology has been in retinal prosthesis, with a headset illuminating a newly photosensitized layer in a dysfunctional retinae. This research paper explores a new type...

We present a reconfigurable neural processor for real-time simulation and prediction of opto-neural behaviour. We combined a detailed Hodgkin-Huxley CA3 neuron integrated with a four-state Channelrhodopsin-2 (ChR2) model into reconfigurable silicon hardware. Our architecture consists of a Field Programmable Gated Array (FPGA) with a custom-built co...

This paper presents the research on the machinability studies in micro-milling of (001) silicon wafer. Excessive generation of undesirable surface and subsurface damages such as surface edge chipping often occurs when machined at depth of cut of several hundreds of microns. Ideal machining strategy to reduce the generation of edge chipping is requi...

The human visual cortex has evolved to determine efficiently objects from within a scene. Hierarchical MAX (HMAX) is an object recognition model which has been inspired by the visual cortex, and sparse coding, which is a characteristic of neurons in the visual cortex, was previously integrated into the HMAX model for improved performance. In this w...

This paper proposes a 10 bit fixed window asynchronous Level Crossing ADC that exhibits a power consumption profile proportional to its input signal's rate of change. The ADC utilizes a fixed voltage window, level crossing slope detector to trigger the generation of non uniformly spaced samples that are compared to a ramp voltage for the conversion...

This article presents the research on the effect of crystallographic orientation and different cutting tool effect during micro-milling of (001) silicon wafer. Excessive generation of undesirable surface and subsurface damages often occurs when machined at thick depth of cut of several hundreds of microns. Up-milling operations along <100> and <110...

The hierarchical MAX (HMAX) model of human visual system has been used in robotics and autonomous systems widely. However, there is still a stark gap between human and robotic vision in observing the environment and intelligently categorizing the objects. Therefore, improving models such as the HMAX is still topical. In this work, in order to enhan...

The loss of hand profoundly affects an individual's quality of life. Prosthetic hands can provide a route to functional rehabilitation by allowing the amputees to undertake their daily activities. However, the performance of current artificial hands falls well short of the dexterity that natural hands offer. The aim of this study is to test whether...

Implantable neuro-prosthetics considerable clinical benefit to a range of neurological conditions. Optogenetics is a particular recent interest which utilizes high radiance light for photo-activation of genetic cells. This can provide improved biocompatibility and neural targeting over electrical stimuli. To date the primary optical delivery method...

The cerebellum plays a critical role for sensorimotor control and learning. However, dysmetria or delays in movements' onsets consequent to damages in cerebellum cannot be cured completely at the moment. Neuroprosthesis is an emerging technology that can potentially substitute such motor control module in the brain. A pre-requisite for this to beco...

Retinitis pigmentosa (RP) is a progressive retinal dystrophy that causes visual impairment and eventual blindness. Retinal prostheses are the best currently available vision-restoring treatment for RP, but only restore crude vision. One possible contributing factor to the poor quality of vision achieved with prosthetic devices is the pathological r...

In this paper, the wireless data and power transfer for a novel optogenetic visual cortex implant system was demonstrated by using pork tissue mimic in-vitro at the ISM 2.4 GHz and 13.5 MHz frequency band respectively. The observed data rate was 120 kbps with no loss in data for up to a thickness of 35 mm in both water & pork. To increase the power...

In this work we explore the extent at which power gating in asynchronous micropipelines is beneficial at low operating voltages at different input data rates. In addition we present a further improvement to previous techniques by adding the delay blocks to the power gated voltage domains to reduce the leakage energy consumed by these blocks. An asy...

This paper presents an experimental investigation on surface and subsurface characterisation of micro-machined single-crystal silicon with (100) orientation. Full immersion slot milling was conducted using solid cubic boron nitride (CBN) and diamond-coated fine grain tungsten carbide micro-end mills with a uniform tool diameter of 0.5 mm. The micro...

Pattern-adjustable optrode based on optical waveguide mode selection is proposed for optogenetics. Multi-mode silica-on-silicon waveguide is used for demonstration to observe adjustable output patterns for at least 6 adjustable main propagating modes in the waveguide.

Sensorimotor control and learning require the function of sophisticated neural system. Cerebellum is one such brain region which comprises more than half of the total neuron population in the entire brain. Capable of simulating a bio-realistic cerebellum model provides important information for neuroscience and engineering. Here we present a Networ...

One of the key challenges in the optogenetic field is to develop novel optical delivery devices that have the feasibility for implantable neural stimulation. In this paper, a CMOS-Gallium Nitride based optrode is proposed for neural stimulation with optogenetic methodology. The optrode base unit has been designed in a X-Fab 0.35um CMOS process and...

Optogenetic forms of retinal prosthesis promise higher resolutions and more precise neural coding than electronic implants. This is predicated on high resolution, high radiance optoelectronic illuminators. In this paper, we describe a 90×90 CMOS driven micro light emitting diode (LED) array. Our device is implemented on a 0.35 μm CMOS process combi...