Fabrication and Application of a Polymer Neuromorphic Circuitry Based on Polymer Memristive Devices and Polymer Transistors

Neuromorphic engineering is a discipline that aims to address the shortcomings of today\u27s serial computers, namely large power consumption, susceptibility to physical damage, as well as the need for explicit programming, by applying biologically-inspired principles to develop neural systems with applications such as machine learning and perception, autonomous robotics and generic artificial intelligence. This doctoral dissertation presents work performed fabricating a previously developed type of polymer neuromorphic architecture, termed Polymer Neuromorphic Circuitry (PNC), inspired by the McCulloch-Pitts model of an artificial neuron. The major contribution of this dissertation is a development of processing techniques necessary to realize the Polymer Neuromorphic Circuitry, which required a development of individual polymer electronics elements, as well as customization of fabrication processes necessary for the realization of the circuitry on separate substrates as well as on a single substrate. This is the first demonstration of a fabrication of an entire neuron, and more importantly, a network of such neurons, that includes both the weighting functionality of a synapse and the somatic summing, all realized with polymer electronics technology. Polymer electronics is a new branch of electronics that is based on conductive and semi-conductive polymers. These new elements hold a great advantage over the conventional, inorganic electronics in the form of physical flexibility, low cost and ease of fabrication, manufacturing compatibility with many substrate materials, as well as greater biological compatibility. These advantages were the primary motivation for the choice to fabricate all of the electrical components required to realize the PNC, namely polymer transistors, polymer memristive devices, and polymer resistors, with polymer electronics components. The efficacy of this design is validated by demonstrating that the activation function of a single neuron approximates the sigmoidal function commonly employed by artificial neural networks. The utility of the neuromorphic circuitry is further corroborated by illustrating that a network of such neurons, and even a single neuron, are capable of performing linear classification for a real-life problem

Simulation, Application, and Resilience of an Organic Neuromorphic Architecture, Made with Organic Bistable Devices and Organic Field Effect Transistors

This thesis presents work done simulating a type of organic neuromorphic architecture, modeled after Artificial Neural Network, and termed Synthetic Neural Network, or SNN. The first major contribution of this thesis is development of a single-transistor-single-organic-bistable-device-per-input circuit that approximates behavior of an artificial neuron. The efficacy of this design is validated by comparing the behavior of a single synthetic neuron to that of an artificial neuron as well as two examples involving a network of synthetic neurons. The analysis utilizes electrical characteristics of polymer electronic elements, namely Organic Bistable Device and Organic Field Effect Transistor, created in the laboratory at University of Denver. Polymer electronics is a new branch of electronics that is based on conductive and semi-conductive polymers. These new elements hold a great advantage over the inorganic electronics in the form of physical flexibility and low cost of fabrication. However, their device variability between individual devices is also much greater. Therefore the second major contribution of this thesis is the analysis of resilience of neural networks subjected to physical damage and other manufacturing faults

Modeling of the Electrical Characteristics of an Organic Field Effect Transistor in Presence of the Bending Effects

An analytical model incorporating the density of trap states for a bendable organic field effect transistor (OFET) is presented in this paper. The aim of this work is to propose a novel modeling framework to quantitatively characterize the bending effects on the electrical properties of an OFET in the linear and saturation regimes. In this model, the exponentially distributed shallow trap states are introduced into the Poisson equation to describe the carrier transports in the channel. The carrier mobility takes into account the low field mobility enhancement under gradual channel approximation and high field degradation. As a result, the generalized current-voltage transistor equations are derived for the first time to reflect the transconductance relationships of the OFET with trap states. In addition, an electro-mechanical coupling relationship is established per the metaphorical analogy between inorganic and organic semiconductor energy band models to quantify the stress-induced variations of the carrier mobility, and the threshold voltage. It is revealed that the before- and after-bending transconductances, predicted from the derived analytical model, are in good agreement with the experimental data measured from DNTT-based OFET bending tests

Organic Log-Domain Integrator Synapse

Synapses play a critical role in memory, learning, and cognition. Their main functions include converting presynaptic voltage spikes to postsynaptic currents, as well as scaling the input signal. Several brain-inspired architectures have been proposed to emulate the behavior of biological synapses. While these are useful to explore the properties of nervous systems, the challenge of making biocompatible and flexible circuits with biologically plausible time constants and tunable gain remains. Here, a physically flexible organic log-domain integrator synaptic circuit is shown to address this challenge. In particular, the circuit is fabricated using organic-based materials that are electrically active, offer flexibility and biocompatibility, as well as time constants (critical in learning neural codes and encoding spatiotemporal patterns) that are biologically plausible. Using a 10 nF synaptic capacitor, the time constant reached 126 and 221 ms before and during bending, respectively. The flexible synaptic circuit is characterized before and during bending, followed with studies on the effects of weighting voltage, synaptic capacitance, and disparity in presynaptic signals on the time constant

Thin Film Cocaine Sensors

Over 7 million Americans suffer from a drug use disorder and up to 60% of individuals treated for addiction will ultimately relapse. We are developing ultra-thin film electrodes on a wearable substrate for a sensor that can detect minute amounts of cocaine in sweat droplets secreted from the skin. This will enable wearable drug monitoring for personalized rehabilitation treatment plans and improve long-term addiction recovery rates. The current research focuses on developing a thin-film sensor that can be applied directly to the skin. First a layer of PVP (poly4-vinylphenol) was prepared and then spun coated onto a piece of glass. This adhesive coated glass acted as a substrate for assembling the sensors. Silver reference electrodes were generated by evaporating silver through a stencil, which contained 1mm by 10mm slits, in a vacuum sealed chamber. The resulting electrodes were tested to verify their conductivity, stability, and reactivity. Upon successfully demonstrating these characteristics, a second stencil was made to evaporate both gold and silver to make a working electrode surface that will react with a cocaine solution, making the first prototype that can successfully detect cocaine

A Shift from 2D Design Paradigm of the 19 th Century to 3D/CityGML, BIM, 3D Printing and Some of Smarter Cities in Poland

A road from paper-based-administration of the 80-ties to Smart Cities of today is being showed in this paper. Shift from paper do digital environment started with regaining of Polish independence in 1989, 26 years ago. The first e-mail from Poland was sent in 1990 year, 19 years after the first e-mail on the world of Ray Tomlinson (1971). Transfter of legal responsibilities, legal power, competences and finance from the top to local levels resulted in revolution in IT sector, which was the first commercial sector running in apost comunist country, in the 80-ties and the beginning of 90ties.Pressure for changes was visible exspecially in the biggest cities, and were initially connected with process of “mucicipalization” – i.e. – transfering of ownership of land from the state level to the level of municipalities. Signum Tempori of this time, was a process of transfer of state owned land to the city property of the City of Gdansk, where more than 30000 real estates of of the market value of 750 million US dollars were transferred and became municipal between 1992 and 1994 years. More and more LIS (Land Information Systems) and GIS (Geographic Information Systems) were implemented, without interoperability rules and standards. Lack of ability to adapt centrain common standards between State Surveying and the biggest cities resulted in appearance of more than 20 graphical applications and more then 20 textual databases applications which required later substantial efforts and costs to overcome information chaos. 10 biggest metropolitan Polish Cities spend more then 3 times than the General Office of Geodesy and Cadasrte of Poland, between 1991 and 1994. Gradual implementaion of INSPIRE Directive and the Law of National Infrastrructure of Spatial Information created unprecedented shitf from paper maps and paper records to almost all digital Poland. Expenditures of c.a. 650 million PLN were assigned to creation of digital representaion of all 34 data layers of INSPIRE Directive for the impelmentaion period of 2010 to 2019. Nevertheless, this amount has been almost doubled in the first 3 years, taking into acccount expenditures of only regional and local GIS/SDI Projects. Polish spatial and economic conditions created spatio-economic background, within which more than 65 % of GDP of Poland is located within 12 metropolitan areas, and at the same time around 67 % of Polish GDP is being generated by more than 4 million of micro or small businesses (often small “family” businesses.).Polish Spatial Planning Law of 2003 has weakened spatial planning regulation, allowing for certain “exception from the rule”, which became a new rule in itself. Basically, this “door” in the law to obtain building permint outside the borders of local development plan – resulted in issuing of more than 700 000 building permits – all located ouside territories of local spatial development plans between 2003 and 2015. Therefore we observe freely flowing process of urban sprawl on one hand and increased land consumption, expecially in the peri-urban zones of all metropolitan cities, and on the other hand, from the economic point of view – Poland has experienced unprecedented GDP growth in recent 10 or 12 years. Nevertheless several really interesting projects have been kicked-off by metropolitan cities, regions and General Survey of Poland (GUGIK). One of the most interesting projects – ISOK (Informatic System of State Protection against Extraordinary Threads) was impelmented between 2011 and 2015, at the cost of c.a. 300 million PLN, resulting in creation of laser scanning data for 92 % of territory of Poland. Continuation of this project was secured in the autumn of 2015 year, devoting budget of 189 million PLN for the project called CAPAP (acronyme from “ Centre of Spatial Analysis of Public Administration), which aim is to provide 3D model of all buildings in Poland, in compliance with CityGML LOD 2 (second Level of Detail), withing the time frame 2016 – 2018. So, all territory of Poland will become 3D in 3 years time in accordance with CityGLM LoD2 and some studies and pilot projects going in this direction are being described in this paper. Some recent exercises with 3D printing of new urban projects are being reported at the end of article

270 nm Ultra-Thin Self-Adhesive Conformable and Long-Term Air-Stable Complimentary Organic Transistors and Amplifiers

Lightweight, flexible, and conformal bioelectronics are essential for wearable technologies. This paper introduces 270 nm thin organic electronics amplifying circuits that are self-adhesive, skin conformal, and long-term air-stable. This report studies the effect of total device thickness, namely 3 μm and 270 nm devices, on the characterization of organic devices before and after buckling, the longevity of organic field-effect transistors (OFETs) over 5 years, and the lamination of OFETs on the human skin. A single-stage organic complementary inverter and a pseudo-complementary amplifier are fabricated to compare their electrical characteristics, with amplification gains of 10 and 64, respectively. Finally, the study demonstrates a five-stage organic complementary inverter can successfully amplify artificial electromyogram and electrocardiogram signals with gains of 1000 and 1088, respectively

An organic synaptic circuit: toward flexible and biocompatible organic neuromorphic processing

In the nervous system synapses play a critical role in computation. In neuromorphic systems, biologically inspired hardware implementations of spiking neural networks, electronic synaptic circuits pass signals between silicon neurons by integrating pre-synaptic voltage pulses and converting them into post-synaptic currents, which are scaled by the synaptic weight parameter. The overwhelming majority of neuromorphic systems are implemented using inorganic, mainly silicon, technology. As such, they are physically rigid, require expensive fabrication equipment and high fabrication temperatures, are limited to small-area fabrication, and are difficult to interface with biological tissue. Organic electronics are based on electronic properties of carbon-based molecules and polymers and offer benefits including physical flexibility, low cost, low temperature, and large-area fabrication, as well as biocompatibility, all unavailable to inorganic electronics. Here, we demonstrate an organic differential-pair integrator synaptic circuit, a biologically realistic synapse model, implemented using physically flexible complementary organic electronics. The synapse is shown to convert input voltage spikes into output current traces with biologically realistic time scales. We characterize circuit’s responses based on various synaptic parameters, including gain and weighting voltages, time-constant, synaptic capacitance, and circuit response due to inputs of different frequencies. Time constants comparable to those of biological synapses and the neurons are critical in processing real-world sensory signals such as speech, or bio-signals measured from the body. For processing even slower signals, e.g., on behavioral time scales, we demonstrate time constants in excess of two seconds, while biologically plausible time constants are achieved by deploying smaller synaptic capacitors. We measure the circuit synaptic response to input voltage spikes and present the circuit response properties using custom-made circuit simulations, which are in good agreement with the measured behavior