This PDF file contains the front matter associated with SPIE Proceedings Volume 11096, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Through the use of solution‐based materials, the field of printed electronics has not only made new devices accessible, but enabled the process of manufacture to move towards a high-throughput industrial scale. However, while the solution‐based active layer materials employed in these types of systems have been studied quite intensely, the conducting structures that feature in printed circuits, RFID applications, logic systems and electrodes in optoelectronic devices have not received as much attention. Inkjet-printing in particular, as an additive, upscalable, direct write technique that requires no masks or lithographic pre-patterning of substrates, has been utilized to produce such structures in a wide variety of (opto)electronics, paving the way to fully solution-processed devices. However, for full compatibility with flexible, low cost substrates, the processing conditions of the deposited structures need to be controlled. This contribution highlights our work on utilizing inkjet-printing to deposit copper nanoparticles (CuNPs) in order to form conducting structures within a range of electronic applications, specifically optoelectronic devices and printed circuits, and discusses methods to improve the conductive and interfacial properties. A reductive sintering approach is presented as an alternative to commonly used laser or flash lamp curing techniques. The findings presented address the importance of continuing work in improving the effectiveness of printed conductive structures, including in their use in organic and hybrid (opto)electronic devices, in order to move towards fully solution-processed and flexible electronics.

Previous studies have demonstrated the use of crystalline organic semiconductors to detect and localize the passage of charged particles and energetic radiation. [1-6] In this context, polycrystalline bis-(triisopropylsilylethynyl)pentacene (TIPS-pentacene) was printed onto polyethylene naphthalate (PEN) substrates patterned with parylene-C dielectric, PEDOT electrodes and gold pads to form fully organic flexible x-ray detectors. The electrodes were patterned using orthogonal photolithography and oxygen reactive ion etching to define a width/length (W/L) = 100 µm/10 µm. An organic voltage divider built using these materials was hot bar bonded to a printed circuit board (PCB) via a flexible conducting tape to form a complete sensor system. The devices were irradiated with a variety of localized and large area sources and the output was extracted from the node between the two resistors and then connected to an operational amplifier via a second PCB. Dark currents for each resistor were in the 100 pA - 1 nA range. The device demonstrated has the potential to be applied in microdosimetry to allow for detection using a cross-section that matches organic tissue forming a solid state tissue equivalent detector (SSTED) [7]. References: [1] Beckerle, P. and Ströbele, H., 2000. Charged particle detection in organic semiconductors. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 449(1-2), pp.302-310. [2] Fraboni, B., Ciavatti, A., Merlo, F., Pasquini, L., Cavallini, A., Quaranta, A., Bonfiglio, A. and Fraleoni‐Morgera, A., 2012. Organic Semiconducting Single Crystals as Next Generation of Low‐Cost, Room‐Temperature Electrical X‐ray [3] Detectors. Advanced Materials, 24(17), pp.2289-2293. Intaniwet, A., Keddie, J.L., Shkunov, M. and Sellin, P.J., 2011. High charge-carrier mobilities in blends of poly (triarylamine) and TIPS-pentacene leading to better performing X-ray sensors. Organic Electronics, 12(11), pp.1903-1908. [4] Kane, M.C., Lascola, R.J. and Clark, E.A., 2010. Investigation on the effects of beta and gamma irradiation on conducting polymers for sensor applications. Radiation Physics and Chemistry, 79(12), pp.1189-1195.. [5] Lai, S., Cosseddu, P., Basiricò, L., Ciavatti, A., Fraboni, B. and Bonfiglio, A., 2017. A Highly Sensitive, Direct X‐Ray Detector Based on a Low‐Voltage Organic Field‐Effect Transistor. Advanced Electronic Materials, 3(8), p.1600409. [6] Schrote, K. and Frey, M.W., 2013. Effect of irradiation on poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonate) nanofiber conductivity. Polymer, 54(2), pp.737-742. [7] Bardash, M., 2010, August. An organic semiconductor device for detecting ionizing radiation on a cellular level. In Organic Semiconductors in Sensors and Bioelectronics III (Vol. 7779, p. 77790F). International Society for Optics and Photonics.

The reaction center (RC) protein from photosynthetic purple bacteria is an organic structure with the capability of absorbing photons at low light intensities and generating electron-hole pairs with a high efficiency. Application of this biomaterial for energy harvesting and sensor devices has been studied before. A key in employing RCs in an electrochemical device is to immobilize the proteins on an electrode. In this work, ion-sensitive field-effect transistors with Si₃N₄ and TaO₂ gate insulator were tested to measure the success rate in immobilizing the proteins. The results show that by far Si₃N₄ is a better choice than TaO₂, due to the effective self-assembly of the linker molecules. The density of the attached proteins to the Si₃N₄ transistor was estimated to be 5×10⁹ proteins/cm² by analyzing the drift in the threshold voltage of the transistor. The fabricated device also presented the feasibility of using the RCs in an integrated photo-transistor.

Soft conjugated polymer composites are attractive for broad future semiconductor-based devices due to their inherent advantages such as lightweight, flexible shape, low-cost, ease of processability, ease of scalability, biocompatibility, etc. Similar to traditional inorganic semiconductors, the addition of certain minority dopants can significantly alter the electronic structures and properties of the host conjugated polymers or composites allowing tunability for a variety of potential applications including, but may not limited to, electronic devices (e.g., field effect transistors and related sensors), thermoelectric devices (e.g., temperature sensors, thermoelectric generators), etc. In this work, the design and working principle of a thermo-electric/field effect dual conversion and modulation composite and device are described and demonstrated. Specifically, a thermoelectrically doped P3HT composite was fabricated into a field effect transistor device, and it was observed that both gate voltage and temperature can effectively modulate the source-drain IV or on/off ratios, i.e., a potential dual sensing and modulation device is demonstrated. The results and findings of this study could be very useful to understand and to guide the design and development of future generation high efficiency molecular or polymer based multi-function sensory or modulation devices.

We summarize our recent results on material, device, and circuit structures for detection of volatile analytes in the atmosphere and proteins in aqueous solution. Common to both types of sensing goals is the design of materials that respond more strongly to analytes of interest than to likely interferents, and the use of chemical and electronic amplification methods to increase the ratio of the desired responses to the drift (signal/noise ratio). Printable materials, especially polymers, are emphasized. Furthermore, the use of multiple sensing elements, typically field-effect transistors, increases the selectivity of the information, either by narrowing the classes of compounds providing the responses, distinguishing time-dependent from dose-dependent responses, and increasing the ratio of analyte responses to environmental drifts. To increase the stability of systems used to detect analytes in solution, we sometimes separate the sensing surface from the output device in an arrangement known as a remote gate. We show that the output device may be an organic-based or a silicon-based transistor, and can respond to electrochemical potential changes at the sensing surface arising from a variety of chemical interactions.

In the past few years, with the advance of laser technology, laser engraving has been considered as an alternative method to traditional lithography in the fabrication of microfluidic devices. Considering solution-based method as the main technique for perovskite deposition, the capillary motion of perovskite precursor can be employed for filling a laser-engraved patterned conducting layer. Herein, we used CO₂ laser micromachining for the fabrication of the perovskite photodetector. First, several microchannels were formed by laser engraving of indium tin oxide (ITO) coated polyethylene terephthalate (PET) substrates. Power, speed and frequency parameters of the laser were varied in order to achieve the desired channel roughness. The samples were characterized by scanning electron microscope (SEM) and potentiostat. The I-V characteristics and bode plots of the sample showed a capacitive and an inductive behavior. Finally, a simulation tool was used to analyze the experimental data. This approach offers a simple, rapid and low-cost fabrication method for perovskite photodetector and can be used in large-scale commercial application.

It is now well recognized that traditional computing systems based on von Neumann architecture are not efficient enough to manipulate and process the massive amount of data produced by the contemporary information technologies. A shifting paradigm from the traditional computing systems is the emulation of the brain computational efficiency at the hardware-based level, a field that is also known as neuromorphic computing. Although neuromorphic computing with inorganic materials has been advanced over the past years, nevertheless biological plausibility is questionable in many cases of solid-state technologies. In the brain, for instance, neural populations are immersed in a common electrolyte or cerebrospinal fluid and this fact equips the brain with more efficient features in processing when compared to electronic devices or circuits. Due to this topology in biological neural networks, higher order phenomena exist such as global regulation of neural activity and communication between different regions in the brain mediated by the presence of the global electrolyte. In this work, device concepts will be presented that lead to biological plausibility in organic neuromorphic devices, including global phenomena and synchronization functions. Introducing this level of biological plausibility, paves the way for new concepts of neuromorphic communication between different subunits in a circuit.

Unlike the binary logic of conventional circuitry, the brain relies on the adjustment of continuous synaptic weights to integrate complex stimuli, perform computations, and instruct an appropriate response.[1] Recently, organic electrochemical transistors (OECTs) have been established as an interesting analog synaptic mimic capable of exhibiting several memory functionalities.[2] The existing technology, however, still relies on static, pre-fabricated circuitry that cannot rewire itself in response to a stimulus. Here, we report an evolvable OECT that is formed in situ by electropolymerizing a self-doped conjugated monomer as the transistor channel. Fabrication by means of electropolymerization allows for a stimulus-driven formation of new electronic synapses, which, in the biological sphere, is a major contributor to neuroplasticity. Lasting changes in channel properties can be achieved by either growing additional channel material to enhance conductance or by over-oxidizing the channel to reduce conductance, which is analogous to long-term potentiation and depression, respectively. Transient changes in channel conductance, analogous to short-term potentiation and depression, are attained by inducing non-equilibrium doping states within the transistor channel. We incorporate the synaptic transistor into an evolvable learning circuit that acts as an electronic mimic of classical conditioning by linking an irrelevant input to a response by presenting it simultaneously with a relevant input. The simplicity of this circuit, which consists of a transistor in series with a resistor, is not attainable with existing technology. The reduction in complexity and footprint provided by evolvable hardware has potential to bring about a paradigm shift in the field of machine learning. [1] J. I. Gold, M. N. Shadlen, Trends Cogn. Sci. 2001, 5, 10. [2] a. Y. van de Burgt, E. Lubberman, E. J. Fuller, S. T. Keene, G. C. Faria, S. Agarwal, M. J. Marinella, A. A. Talin, A. Salleo, Nature Mater. 2017, 16, 414; b. P. Gkoupidenis, D. A. Koutsouras, G. G. Malliaras, Nature Comm. 2017, 8.

Organic bioelectronics, as sensors and actuators, provide unique functions when applied to biology and also humans, in the latter case targeting future health care. Here, a body area network is reported including organic sensor nodes, recording relevant health status parameters, and implantable actuators for delivery of pharmaceuticals. These are then included within electronic skin patches also comprising body-coupled communication protocols that transmit and receive information, via capacitive coupling, that is transported through the body. In a parallel communication pathway, sensor and actuator information is also collected into a Bluetooth-based unit for further transfer to cloud computing. While in the cloud, deep learning improve the sensor-to-actuator decision-making. Our complete system is the first in its kind, based on organic and Si-chip technology, performing sensory-regulated delivery of pharmaceuticals, supported by cloud connectivity and machine learning.