Loren Rieth, PhD

Dr. Loren Rieth is currently appointed as Associate Professor in the Center for Bioelectronic Medicine at the Feinstein Institute for Medical Research and in the Department of Neurosurgery at the Hofstra Northwell School of Medicine. His work focuses on research, development, design, fabrication, and testing of neural interface systems and technologies. This includes optical, electrical, and ultrasonic interfaces, and understanding their underlying mechanisms to improve their safety and efficacy for pre-clinical and clinical applications. Prior to joining the Feinstein Institute, Dr. Rieth had an appointment at the University of Utah, where his research focused on the Utah Electrode Array (UEA), and variations on this device architecture, as well as semiconductor-based sensors, microfabrication, materials and surface analysis, photovoltaic devices (solar cells), and epitaxial growth of III-V semiconductors for optoelectronic applications.

His research is focused on wired and wireless neural interface hardware for the central and peripheral nervous system primarily based on the Utah electrode array architecture. This includes arrays designed to interface the central and peripheral nervous system, and also exploring applications in myoelectric recording and stimulation. These technologies have the promise to enable bionic technologies, profoundly improve communications and quality of life for people with neuromuscular conditions, visual prostheses, and neural modulation in the peripheral nervous system to treat inflammation, mood disorders, hypertension, arrhythmias, and many other conditions. Through NIH and DARPA programs, and research contracts with neurotechnology our team continues to develop new technologies including ASICs, packaging technologies, state of the art encapsulation techniques, to generate interfaces that can deliver clinical impact. These include arrays for cortical recording and stimulation in motor and somatosensory cortex, implantation in peripheral nerves including sciatic, median, pudendal, and implanted into the myocardium for mapping arrhythmias. He is continuing to explore electrode technologies, understanding how the interact with the nervous system, and improving their lifetime.

Dr. Loren Rieth’s primary research is focused on highly effective bi-directional neural interfaces to the central, peripheral, and autonomic nervous systems. His goal is to perform research at levels from basic science through device translation to develop neural interface technologies as both tools for basic research and as marketed neuroprosthetic and neuromodulatory devices. Applications include the host of targets being explored through autonomic nerve modulation, motor functions, disarticulation, sensory restoration, micturition, pain, and spasticity. At the Feinstein Institute, his work will include 1) electrical characteristics of electrode/tissue interface; 2) device fabrication (MEMS) research; 3) packaging; 4) materials for electrodes, optrodes, and encapsulation; 5) interface stability (biotic and abiotic); and 6) fundamental aspects of tissue activation with microelectrodes. Investigations of tissue activation will focus on selectivity for different cell types (e.g. a-fiber vs. c-fiber), enabling more biofidelic stimulation, exploring stimulation, blockade and modulation paradigms, and improving the stability, reliability, and specificity of stimulation. Improving the safety and efficacy of devices for these indications will require highly collaborative efforts amongst biomedical, materials, and electrical engineers, as well as neuroscientists, electrophysiologists, (bio-electro-) chemists, geneticist/virologists, clinicians, and surgeons.

Dr. Rieth’s prior work has centered on the Utah Electrode Array (UEA) architecture, and enhancing its capabilities through improving its performance and lifetime, extending its capabilities through integrated electronics, and enabling new methods to interface with the nervous system. This work is currently funded through DARPA and NIH grants, and industrial contracts through the Center for Engineering Innovation. His DARPA/BTO HAPTIX program is focused on improving the tip metallization impedance and compatibility with long term stimulation. Dr. Rieth and his team has decreased the impedance >10x and dramatically increased stimulation current delivery and lifetime. The NIH grant is investigating improvement of electrode encapsulation using atomic layer deposition techniques, and has achieved >5x increase in lifetime of test structures. The BRAIN Initiative U01 just started, and is focused on integrating light sources (µLEDs) and electrophysiological recording capabilities on glass versions of the Utah Array. Lastly, the DARPA Seedling was recently started, and we are investigating SiC as an improved encapsulation material, and also pushing IrOx for long-term stimulation and recording stability.

Dr. Rieth’s current, pending, and completed research has led to active collaborations which include Profs. Solzbacher, Tathireddy, Walker, and Blair, Clark, Normann, Warren, and Dorval, Hutchinson, Mahan, Angelucci, and House from Utah. At the Feinstein Institute, he is collaborating with Bouton, Sohal, Datta, Straka, Zanos, Zanos, Tracey, Grande, and many others to advance neural interfaces to the autonomic system, and improve neural by-pass technologies. In addition, he is developing collaborations with the CUNY Nanofabrication Lab, Cold Spring Harbor Labs, and several companies to further develop a portfolio of neural technologies.

Autonomic Nervous System Interfaces

Interfaces for the autonomic nervous system (ANS) is a core interest for my research. The applications/indications-of-use for these interfaces include inflammation (e.g. rheumatoid arthritis), cardiac function/rhythm, reactive airways (e.g. asthma), obesity/metabolism, homeostatis, etc. The complexity of the ANS has made research and therapies a tremendous challenge.

Dr. Rieth is working with the Center for Bioelectronic Medicine team to develop novel neural interface systems and technologies. Additionally, he is actively reaching out to collaborators to develop a team with the needed physiological, surgical, and hardware/systems components.He is  currently involved in contracts to develop these technologies, and is targeting the SPARC and ElectRx initiatives from NIH and DARPA, respectively, to acquire additional resources for this research. The number of patients with conditions that can be treated by such therapies is large, and several are difficult to treat with drugs due to side-effects or lack of efficacy, making this a highly fulfilling area of research.

Microsystems for Electrophysiology

Dr. Rieth’s research on chronic neural electrophysiology is focused on developing electrodes and architectures capable of delivering and controlling a lifetime of safe, stable, and efficacious recording and stimulation of neural signals. This continues to be a critical need to enable truly bi-directional penetrating neural interfaces that can be used chronically for applications such as neuroprosthetics and highly specific autonomic neuromodulation therapies, and would continue to be a core goal of my research at Utah. He is currently Co-I of a DARPA award titled “Embodied Neuroprosthesis.” This project utilizes an advanced DEKA LUKE Hand prosthetic with 6+ degrees-of-freedom and 10+ sensor outputs (pressure, temperature, joint angles and velocities) with human patients, where the subjects take the prosthesis home for a 1-year period in the 5th year of the program. The prosthesis is controlled by motor efferent signals (neural and/or myoelectric), and sensory and proprioceptive afferents are stimulated to improve metrics associate with activities of daily living, and engender a sense of embodiment towards the prosthesis. His work on this project focuses on improving the electrode metallization of Utah Slanted Electrode Arrays (USEAs) to make them robust and stable for chronic recording and stimulation of neural signals. Specifically, He has observed degradation of the electrode metal and dissolution of the Si electrodes yield profound damage to the electrode tips during both recording and stimulation experiments.

Dr. Rieth believes this strongly contributes to the loss of single-unit recordings from these devices. His program is developing improved metallizations through process and materials improvements to stabilize it as a mechanical and chemical barrier for the electrode, and to prevent damage to this layer by improved processing and heat treatment processes. The current DARPA project involves translation of this work to Blackrock Microsystems to enable GMP (good manufacturing practices) compliant manufacturing of the sensors to bring these technologies to the marketplace. He is also responsible for the EFS-IDE submission required to perform the human subjects studies for this program, and recently submitted our first pre-submission to the FDA as part of initiating this study.

The IrOx for neural electrodes also has many benefits for cardiac electrophysiology due to its low impedance to facilitate recording, and high charge injection capacity for pacing applications. Dr. Rieth recently had a sponsored project titled “Electrode materials for atrial fibrillation mapping catheters” with a small business concern bringing an innovative cardiac mapping catheter to market. The low impedance and stable properties of IrOx make it a very strong choice for sensitive mapping catheters, allowing use of smaller and more selective electrode sites, or working with the smaller signals available further from the endocardium. Improved mapping coupled with the associated improved understanding of pathological conduction pathways has the potential to significantly improve the long-term benefits of RF ablation procedures. He plans to expand this effort towards tightly integrating IrOx coatings with state-of-the-art leads and catheters to improve their performance, reliability, and safety to improve arrhythmia treatment.

Encapsulation

The use of increasingly complex implanted electronics will be required for the development of next generation research tools and marketed devices able to deliver the greater specificity needed to address the complexity of the central and peripheral nervous systems. Development of improved encapsulation schemes is critical for both the implanted electronics, and the neural interface front-end components to enable high-channel-count stimulation and recording systems.

Dr. Rieth’s work on encapsulation was funded by an NIH/NIBIB SBIR in collaboration with Blackrock Microsystems titled “Plasma-assisted atomic layer deposition of alumina and Parylene-C bi-layer encapsulation,” for which he led the scientific effort at Blackrock Microsystems. This lab-to-market (2-year) SBIR seeks to extend the dramatic improvements in UEA encapsulation we reported through use of Atomic Layer Deposition (ALD) of Al2O3 films in conjunction with Parylene-C, and features extensive in-vitro and in-vivo testing of devices. This project involves extensive failure mode analysis through accelerated lifetime testing to identify failure modes, and perform experiments to mitigate them. As an example, test structures with added topographic elements (e.g. coils, SMD capacitors, wire bonds) and full UEAs are being investigated, and the encapsulation failures localized through use of electrochemical decoration techniques, impedance analysis, and chronoamperometry. These experiments are designed to develop encapsulation schemes that completely suppress the decrease in impedance associated with encapsulation degradation and water ingress that has been widely reported for UEAs. Improved encapsulation technologies are also broadly applicable to electrophysiological implants such as ECoGs, depth-electrodes, neuromodulation products, cuff electrodes, as well as systems with integrated electronics and cardiac EP products.

Dr. Rieth is also pursuing hybrid optogentic and electrophysiological arrays that are able to chronically deliver precise spatio-temporally patterned light to neural tissue. He has received a BRAIN Initiative award to pursue this technology. Dr. Rieth has published several papers related to the development of glass versions of the UEA, and characterization of light coupling, propagation, loss modes, and beam profiles from these devices. This work will integrate micro-LEDs with the optrode arrays, followed by developing techniques to combine optogentic and electrophysiological techniques, with high spatial and temporal specificity. This work has involved collaborations with physiologists (Alessandra Angelucci, Greg Clark, DiCarlo (MIT)), Optics faculty (Steve Blair), and geneticists (Petr Tvrdik). It will explore expression of opsins in the visual cortex, deliver of light to transfected neurons, and perform controlled physiological experiments to understand how stimulation or inhibition can be used for electrophysiological experiments to explore visual circuits.

Dr. Rieth has recently completed a contract with researchers at MIT (James DiCarlo) to develop and build a highly compact implantable LED stimulator for optogentic applications in monkey cortex. This system involved integration of 48 high-brightness micro-LEDs on specialized circuit boards, developing and testing encapsulation techniques, development of a 64-channel constant current LED driver electronics, and the software associated to run the system. This system was developed in conjunction with Blackrock Microsystem, and utilizes their established Cereport connector, and associated leads, for one of the first chronically implanted high-channel-count optical stimulators. The testing and use of this system provides a firm foundation to pursue more sophisticate implants and electronics, to expand the capabilities of optogenetic techniques through BRAIN, SPARC and separate NIH R01 mechanisms.

Future Directions

Dr. Rieth has pursued wireless neural interfaces and neural interfaces with integrated electronics as part of NIH and DARPA programs, as can be seen from my publication record, and would continue with this research at Utah. He has recently submitted large proposals to NSF and NIH to pursue integration of sophisticated electronics with hermetic micropacking with the Utah array. His previous work has included research on improved electrode and encapsulation materials as discussed above, and also involved extensive packaging research used to flip-chip ASICs directly with the UEA, integrate passive components, and testing the systems in-vitro and in-vivo. This work was performed with extensive collaborations with Fraunhofer IZM in Berlin, and Dr. Rieth will continue this productive collaboration going forward. These systems would be bi-directional (recording and stimulation) utilizing specialized ASICs, and would utilize advanced fully-hermetic micropackaging technologies to be developed in collaboration with Frauhofer IZM. These front-end electronics can also be attached to a wide variety of electrodes with different geometries, which is highly beneficial for interfacing with the autonomic nervous system, which has a very heterogeneous anatomical/physiological structure.

Dr. Rieth will be developing internal and collaborative modeling efforts to explore the fundamentals of the electrode tissue interface. This will explore the effects of electrochemistry, materials, and electrotrode architecture on the efficacy of the electrodes for recording, stimulation, and modulation of neural pathways. He will use this knowledge to drive towards the ability to perform the rational design of neural interfaces based on their anatomical and physiological characteristics.

University of Florida
Degree: PhD
2001
Field of Study: Materials Science and Engineering

John-Hopkins University
Degree: BS
1994
Field of Materials Science and Engineering

2001 2nd place Student Poster Competition, Florida Chapter of the American Vacuum Society
1996 2nd place Student Poster Competition, Florida Chapter of the American Vacuum Society

1. R. Caldwell, H. Mandal, R. Sharma, F. Solzbacher, P. Tathireddy, and L. Rieth, “Analysis of Al2O3—parylene C bilayer coatings and impact of microelectrode topography on long term stability of implantable neural arrays,” Journal of neural engineering, vol. 14, p. 046011, 2017.
2.  X. Xie, L. Rieth, R. Caldwell, S. Negi, R. Bhandari, R. Sharma, P. Tathireddy, and F. Solzbacher, “Effect of bias voltage and temperature on lifetime of wireless neural interfaces with Al2O3 and parylene bilayer encapsulation,” Biomedical Microdevices, vol. 17, pp. 1-8, 2015/01/23 2015.
3. X. Xie, L. Rieth, L. Williams, S. Negi, R. Bhandari, R. Caldwell, R. Sharma, P. Tathireddy, and F. Solzbacher, “Long-term reliability of Al2O3 and Parylene C bilayer encapsulated Utah electrode array based neural interfaces for chronic implantation,” J Neural Eng, vol. 11, p. 026016, Mar 24 2014.
4. S. Minnikanti, G. Diao, J. J. Pancrazio, X. Xie, L. Rieth, F. Solzbacher, and N. Peixoto, “Lifetime assessment of atomic-layer-deposited Al2O 3-Parylene C bilayer coating for neural interfaces using accelerated age testing and electrochemical characterization,” Acta Biomaterialia, vol. 10, pp. 960-967, 2014.
5. T. V. Abaya, M. Diwekar, S. Blair, P. Tathireddy, L. Rieth, and F. Solzbacher, “Deep-tissue light delivery via optrode arrays,” J Biomed Opt, vol. 19, p. 15006, Jan 2014.
6. H. A. C. Wark, R. Sharma, K. S. Mathews, E. Fernandez, J. Yoo, B. Christensen, P. Tresco, L. Rieth, F. Solzbacher, R. A. Normann, and P. Tathireddy, “A new high-density (25 electrodes/mm2) penetrating microelectrode array for recording and stimulating sub-millimeter neuroanatomical structures,” Journal of Neural Engineering, vol. 10, 2013.
7. A. Sharma, L. Rieth, P. Tathireddy, R. Harrison, H. Oppermann, M. Klein, M. Topper, E. Jung, R. Normann, G. Clark, and F. Solzbacher, “Evaluation of the packaging and encapsulation reliability in fully integrated, fully wireless 100 channel Utah Slant Electrode Array (USEA): Implications for long term functionality,” Sensors and Actuators A: Physical, vol. 188, pp. 167-172, 2012.
8. A. Sharma, L. Rieth, P. Tathireddy, R. Harrison, H. Oppermann, M. Klein, M. Toepper, E. Jung, R. A. Normann, G. Clark, and F. Solzbacher, “Long term in vitro functional stability and recording longevity of fully integrated wireless neural interfaces based on the Utah Slant Electrode Array,” Journal of Neural Engineering, vol. 8, p. 045004, 2011.
9. S. Negi, R. Bhandari, L. Rieth, R. Van Wagenen, and F. Solzbacher, “Neural electrode degradation from continuous electrical stimulation: Comparison of sputtered and activated iridium oxide,” Journal of Neuroscience Methods, vol. 186, pp. 8-17, 2010.

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