A scalable optoelectronic neural probe architecture with self-diagnostic capability

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 have a simple serial interface rather than large numbers of control lines. This paper demonstrates an optrode structure comprising of a standard complementary metal-oxide-semiconductor process with 18 optical stimulation drivers. Furthermore, diagnostic sensing circuitry is incorporated to determine the long-term functionality of the photonic elements. A digital control system is incorporated to allow independent multisite control and serial communication with external control units

Intrapartum fetal death and doctors; A qualitative exploration

Introduction: The death of an infant during a pregnancy is profoundly traumatic, both for the parents and the involved healthcare professionals. Most research focuses on the impact of antenatal stillbirth with very little research examining the specific impact an intrapartum fetal death has on obstetricians. The aim of this study was to provide an in‐depth qualitative exploration of the attitudes and responses that Irish Obstetricians have following direct involvement with an intrapartum fetal death. Material and methods: Qualitative semi‐ structured interviews were used. Interpretative phenomenology was used for data analysis. The setting was a tertiary university maternity unit in Ireland with 8200 deliveries per year. Ten obstetricians were purposively sampled. The main outcome measures were the attitudes and responses of Irish obstetricians following exposure to an intrapartum death. Results: Obstetricians were profoundly and negatively affected by a personal involvement with an intrapartum death. Analysis of the data revealed two superordinate themes; the doctor as a person, and supporting each other. The doctor as person was characterised by two subordinate themes; emotional impact and frustration. Supporting each other was also characterised by two subordinate themes; an unmet need and incidental support and what might work. Conclusions: Obstetric doctors who are directly involved in an intrapartum death are the second victims of this event and this is something that needs to be acknowledged; by the public, by the healthcare system, by the media and by the doctors themselves. The development of effective emotional support interventions for all obstetricians is highly important

Comparison between different optical systems for optogenetics based head mounted device for retina pigmentosa

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 efficient optical system to focus the transmitted light pattern into the retina surface. In this work, three different lenses; contact lens, folded prism and linear lenses are used to evaluate the headset performance. A 90x90 μLED display is used as a light source and the optical efficiency for each lens is measured for different points over the lens area. Moreover, the impact of each lens on the headset performance in power and processing will be discussed in this work

An efficient telemetry system for restoring sight

PhD ThesisThe human nervous system can be damaged as a result of disease or trauma, causing conditions such as Parkinson’s disease. Most people try pharmaceuticals as a primary method of treatment. However, drugs cannot restore some cases, such as visual disorder. Alternatively, this impairment can be treated with electronic neural prostheses. A retinal prosthesis is an example of that for restoring sight, but it is not efficient and only people with retinal pigmentosa benefit from it. In such treatments, stimulation of the nervous system can be achieved by electrical or optical means. In the latter case, the nerves need to be rendered light sensitive via genetic means (optogenetics). High radiance photonic devices are then required to deliver light to the target tissue. Such optical approaches hold the potential to be more effective while causing less harm to the brain tissue. As these devices are implanted in tissue, wireless means need to be used to communicate with them. For this, IEEE 802.15.6 or Bluetooth protocols at 2.4GHz are potentially compatible with most advanced electronic devices, and are also safe and secure. Also, wireless power delivery can operate the implanted device. In this thesis, a fully wireless and efficient visual cortical stimulator was designed to restore the sight of the blind. This system is likely to address 40% of the causes of blindness. In general, the system can be divided into two parts, hardware and software. Hardware parts include a wireless power transfer design, the communication device, power management, a processor and the control unit, and the 3D design for assembly. The software part contains the image simplification, image compression, data encoding, pulse modulation, and the control system. Real-time video streaming is processed and sent over Bluetooth, and data are received by the LPC4330 six layer implanted board. After retrieving the compressed data, the processed data are again sent to the implanted electrode/optrode to stimulate the brain’s nerve cells

Beyond solid-state lighting: Miniaturization, hybrid integration, and applications og GaN nano- and micro-LEDs

Gallium Nitride (GaN) light-emitting-diode (LED) technology has been the revolution in modern lighting. In the last decade, a huge global market of efficient, long-lasting and ubiquitous white light sources has developed around the inception of the Nobel-price-winning blue GaN LEDs. Today GaN optoelectronics is developing beyond lighting, leading to new and innovative devices, e.g. for micro-displays, being the core technology for future augmented reality and visualization, as well as point light sources for optical excitation in communications, imaging, and sensing. This explosion of applications is driven by two main directions: the ability to produce very small GaN LEDs (microLEDs and nanoLEDs) with high efficiency and across large areas, in combination with the possibility to merge optoelectronic-grade GaN microLEDs with silicon microelectronics in a fully hybrid approach. GaN LED technology today is even spreading into the realm of display technology, which has been occupied by organic LED (OLED) and liquid crystal display (LCD) for decades. In this review, the technological transition towards GaN micro- and nanodevices beyond lighting is discussed including an up-to-date overview on the state of the art

Doctor of Philosophy

dissertationOptical methods are well-established in the fields of neuroscience, medical imaging, and diagnostics, etc. Optogenetics, for example, enables molecular specificity in optical neural stimulation and recording and has been named the "Method of the Year 2010" by Nature Methods. A novel microdevice was designed, fabricated, developed, and tested to facilitate three-dimensional (3D) deep-tissue light penetration with the capacity to accommodate spatiotemporal modulation of one or more wavelengths to advance a broad range of applications for optical neural interfaces. A 3D optrode array consisting of optically transparent "needles" can penetrate >1 mm directly into tissue, thereby creating multiple independent paths for light propagation that avoid attenuation due to tissue absorption and scattering, providing a high level of selectivity and comprehensive access to tissue not available in current interfaces. Arrays were developed based upon silicon and glass. The silicon optrode array is based upon the well-established Utah electrode array architectures and is suitable for near-infrared (NIR) applications; glass optrodes are appropriate waveguides for both visible and NIR wavelengths. Arrays were bulk-micromachined with high-aspect ratio, a process that has not been reported to be applied to glass previously. In addition to device fabrication, extensive laboratory testing was performed with various optical sources to determine loss mechanisms and emitted beam profiles in tissue across the relevant wavelength ranges, with particular focus on performance metrics for optogenetic and infrared neural stimulation applications. Optrode arrays were determined to be amenable to integration with typical neural stimulation and imaging light delivery mechanisms such as optical fibers and microscopes. Glass optrodes were able to transmit light at ~90% efficiency through depths many times greater than the tissue attenuation length, with negligible light in-coupling loss. Si optrodes were determined to be only ~40% efficient with losses mostly from high index contrast, tip backreflection, and taper radiation. The in-coupling technique and optrode geometry may be modified to produce illumination volumes appropriate for various experimental paradigms. While the focus of this work is on optical neural stimulation, optrode array devices have application in basic neuroscience research, highly selective photodynamic therapy, and deep tissue imaging for diagnostics and therapy

The neural engine: a reprogrammable low power platform for closed-loop optogenetics

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 window of 2° C for medical implants and maintain long battery life. In this work, we developed a low power neural engine with an optimized set of algorithms which can operate under a power cycling domain. By integrating with custom designed brain implant chip, we have demonstrated the operational applicability to the closed-loop modulating neural activities in in-vitro brain tissues: the local field potentials can be modulated at required central frequency ranges. Also, both a freely-moving non-human primate (24-hour) and a rodent (1-hour) in-vivo experiments were performed to show system long-term recording performance. The overall system consumes only 2.93mA during operation with a biological recording frequency 50Hz sampling rate (the lifespan is approximately 56 hours). A library of algorithms has been implemented in terms of detection, suppression and optical intervention to allow for exploratory applications in different neurological disorders. Thermal experiments demonstrated that operation creates minimal heating as well as battery performance exceeding 24 hours on a freely moving rodent. Therefore, this technology shows great capabilities for both neuroscience in-vitro/in-vivo applications and medical implantable processing units

Four-Wire Interface ASIC for a Multi-Implant Link

This paper describes an on-chip interface for recovering power and providing full-duplex communication over an AC-coupled 4-wire lead between active implantable devices. The target application requires two modules to be implanted in the brain (cortex) and upper chest; connected via a subcutaneous lead. The brain implant consists of multiple identical “optrodes” that facilitate a bidirectional neural interface (electrical recording and optical stimulation), and the chest implant contains the power source (battery) and processor module. The proposed interface is integrated within each optrode ASIC allowing full-duplex and fully-differential communication based on Manchester encoding. The system features a head-to-chest uplink data rate (up to 1.6 Mbps) that is higher than that of the chest-to-head downlink (100 kbps), which is superimposed on a power carrier. On-chip power management provides an unregulated 5-V dc supply with up to 2.5-mA output current for stimulation, and two regulated voltages (3.3 and 3 V) with 60-dB power supply rejection ratio for recording and logic circuits. The 4-wire ASIC has been implemented in a 0.35-μm CMOS technology, occupying a 1.5-mm 2 silicon area, and consumes a quiescent current of 91.2 μA. The system allows power transmission with measured efficiency of up to 66% from the chest to the brain implant. The downlink and uplink communication are successfully tested in a system with two optrodes and through a 4-wire implantable lead

Micro-optics for Opto-genetic Neuro-stimulation with Micro-LED Arrays

The breakthrough discovery of a nanoscale optically gated ion channel protein, Channelrhodopsin 2 (ChR2), in combination with a genetically expressed optically activated ion pump, Halorhodopsin, allowed the direct stimulation and inhibition of individual action potentials with light alone. This thesis describes the development of optics and micro-optics which when used with micro-led array sources, collects and projects light efficiently and uniformly onto such opto-genetically modified specimens. When used with enhanced light gated ion channels and pumps these systems allow us to further our understanding of both brain and visual systems. Micro-LED arrays permit spatio-temporal control of neuron stimulation on sub-millisecond timescales. However, micro-led arrays are disadvantaged by the broad-angular spread of their light emission and their low spatial fill factor. We present the design of macro and micro-optics systems for use with a micro-LED arrays consisting of a matrix of 25μm diameter micro-LEDs with 150 or 80μm centre-to-centre spacing. On one system, the micro-LED array is imaged onto off-the-shelf micro-optics using macro-optics and in the other system; micro-LED array and custom micro-optics are optimised and integrated together. The two systems are designed to improve the fill-factor from 2% to more than 78% by capturing a larger fraction of the LED emission and directing it correctly to the sample plane. This approach allows low fill factor arrays to be used effectively, which in turn has benefits in terms of thermal management and electrical drive from CMOS backplane electronics. These systems were implemented as an independent set that could be connected to a variety of different microscopes available for Patch-clamp and Multi-electrode measurements. As well, the feasibility of an eye prosthesis was tested using virtual reality optics and a fake eye to stimulate ganglion cells and by doing in-vivo stimulation of the genetically modified retina of a mouse.Open Acces