Paper Electronics Utilizing Screen Printing and Vapor Phase Polymerization

Smart label technology such as indicators is a growing field due to society's demand for Internet of Things devices. New materials and technologies are continuously being discovered and developed in order to provide better resolution, better performance, or more environmentally friendly devices. Within this report, screen printing technology is combined with vapor phase polymerization to synthesize three conductive polymers; poly(3,4‐ethylenedioxythiophene) (PEDOT), polypyrrole (PPy), and polythiophene (PTh). The conductive polymers are created in micrometer resolution and investigated for their electrochromic properties. PEDOT and PPy samples are combined into printed, laminated, transmissive electrochromic displays. The technology is further advanced to establish separate PEDOT, PPy, and PTh all‐printed electrochromic displays using several screen printed layers. The PEDOT displays show improved color retention as compared to displays created with commercially available PEDOT:poly(styrene sulfonate) (PSS) with comparable contrast and switching behavior. All‐printed PPy and PTh electrochromic displays with impressive electrochromic behavior are demonstrated. More complex patterns of 7‐segment displays are created, thereby highlighting flexibility and individually switched sections of the conductive polymers. This research extends the screen printing and vapor phase polymerization combination to other conductive polymers and the potential commercialization of multicolor electrochromic displays that has been otherwise dominated by monochromatic PEDOT:PSS.

Vapor phase polymerization for electronically conductive nanopaper based on bacterial cellulose/poly(3,4-ethylenedioxythiophene)

Conductive polymers have been widely applied as counter electrodes in dye-sensitized solar cells. However, as one of many materials in the conductive polymer family, polypyrrole attracts little attention in this field. In this paper, polypyrrole (PPy) was synthesized by vapour phase polymerization (VPP) and electropolymerization (EP) and these PPys were employed as counter electrodes in dye-sensitized solar cells. Comparing this to the regularly used Pt counter electrode, both of them show good catalytic behaviour in dye-sensitized solar cells though the PPy electrodes have a slightly lower fill factor. Such investigation will broaden the application of conductive polymers in DSCs. Our study indicates that polypyrrole is a good candidate to replace the Pt counter electrode in DSCs. Taking into consideration the regular solvent used in DSCs, it is recommended that an insoluble conductive polymer is a good choice for the counter electrode in DSCs.

Developing high performance Li-ion batteries (LiBs) is of great interest to meet a demand for primary power sources that can operate portable electronic devices, hybrid or full-electric vehicles, and renewable energy storage grids. Among the various electrode materials available for LiBs, silicon has been recognised as the most promising anode material due to its extremely high lithiation capacity (theoretically, 4200 mAh/g for Li4.4Si alloy phase), which is over 10 times higher than that of graphite (372 mAh/g), the traditional anode material in LiBs. Nevertheless, the practical application of Si in the commercialized LiBs is still challenging due to its massive volume variation (approximately 300%) that occurs during electrochemical lithiation/delithiation. The volume variation can result in the fracture and pulverization of Si particles, which eventually causes a loss of an electrical contact between the electrode materials, then finally leading rapid capacity fading during further cycling. In order to address this issue, tremendous attempts have been devoted mostly through structural modification of Si materials, including synthesis of nano-structured Si (nanowires, nanotubes, yolk-shell, and nanoporous Si) and Si-based composite materials using nano-carbon matrix (CNTs, CNFs, and graphene). Owing to the efficient accommodation of the volume variation of Si, which result from the well-designed nanostructure or the buffering effect of the nano-carbon matrix, these Si-based electrodes exhibit the significant improvements in the cycling stability. However these strategies generally involve complicated synthetic steps or require additional materials, thereby their scalability and compatibility remains a challenge under the cost-related practical point of view. Furthermore, the structure-modified Si, electrode active material, cannot stand alone to construct electrode for conventional battery cells. To support the sufficient electrical conductivity and structural robustness into the battery electrodes, a large amount, typically over 30%, of inactive components including conductive agent and polymeric binder is required. However this portion of inactive components is relatively higher than that used for the practical electrode formulations (less than total 20%) and it may result in the decrease in the energy density of LiBs. Given these limitations, increasing attention has been focused on the advancement of the inactive components of battery electrodes. Traditionally, these inactive components possess their own independent functionality. The polymeric binder covers the active materials and conductive agent to mechanically combine together in the entire electrode. And the conductive agent creates the conducting bridges between active materials for their electrochemical utilization. Such a classic electrode system that consists of tri-components (active material, conductive agent, and polymeric binder) is very typical in the conventional LiBs, but it does not suitably work for the Si-based electrodes which have huge volume variation. This is attributed to the break of connections between the non-adhesive conductive agents and the active materials by continuous volume variation. To the end, bi-component electrode system based on dual-functional conducting polymer were further developed to enhance the electrochemical performance of Si-based electrodes. Here, the conducting polymer plays two roles simultaneously not only as a conductive agent but also as a binder, and it can replace the traditional two inactive components by its dual-functionality. This nature of conducting polymer allow to more effectively maintain the continuous electrical network even during huge volume variation of active Si. Additionally, the bi-component electrode that only consists of active Si material and conducting polymer can maximize the energy density of the LiB cells by minimizing portion of total inactive components, which might be great merit of this bi-component system. Based on the above concepts, herein we propose the advanced bi-component Si electrode by employing poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), one of the most common and the successful conducting polymer. PEDOT:PSS is a commercially acquirable polyelectrolyte with excellent physical properties including high electrical conductivity, chemical stability, and mechanically robust. Owing to these great advantages, there has been several effort directed toward developing battery electrodes by exploiting the intrinsic properties of PEDOT:PSS. Here, we report the Si/PEDOT:PSS bi-components electrode via a very simple strategy; the high solubility in water caused by PSS polyanion chains enable the PEDOT:PSS solution to be directly adopted into simple slurry casting technique, the most efficient way that was used in the practical battery electrode manufacturing process. This simple synthesis strategy should allow for the development of Si-electrode, and should also serve as a guide for engineers and scientists engaged in the rational design of electrode system for LIBs.

Conducting polymers (CPs) are increasingly being used to interface with cells for applications in both bioelectronics and tissue engineering. To facilitate this interaction, cells need to adhere and grow on the CP surface. Extracellular matrix components are usually necessary to support or enhance cell attachment and growth on polymer substrates. Here we show the preparation of PEDOT(TOS):gelatin composites as a new biocompatible substrate for use in tissue engineering. Gelatin, a derivative of the extracellular matrix protein collagen, was incorporated into poly(3,4 ethylenedioxythiophene)-tosylate (PEDOT(TOS)) films via vapour phase polymerisation (VPP) without changing the electrochemical properties of the CP. Further, gelatin, incorporated into the PEDOT(TOS) film, was found to specifically support bovine brain capillary endothelial cell adhesion and growth, indicating that the functionality of the biomolecule was maintained. The biocompatibility of the composite films was demonstrated indicating the significant future potential of biocomposites of this type for use in promoting cell adhesion in electrically active materials for tissue engineering.

Facile high-resolution patterning of silver nanowires (AgNWs) is a key enabling technology for expanding their usage to flexible and stretchable electronics applications. Although various patterning methods have been proposed, only high-cost and complex mask-based methods have demonstrated potential micrometer-scale pattern-ability, which have no design freedom of changing patterns in a facile manner. Herein, we suggest a maskless high-resolution patterning method by combining an adhesive underlayer and inkjet-printed conductive polymer patterns. AgNWs located between them are tightly bonded and thus are resistant to a solvent-based rinsing process. AgNWs under the conductive polymer patterns remain while uncovered AgNWs are removed during the rinsing process. Our approach allows easy patterning of AgNWs on various substrates including glass, plastic, and stretchable elastomer. The excellent mechanical properties of AgNW interconnects are demonstrated in a stretchable light-emitting diode array. By introducing an electrohydrodynamic printing method, high-resolution AgNW patterns with linewidths below 20 µm are fabricated, which are used for a heater based on transparent grid AgNW electrodes. Based on our results, we believe that our method paves the way for a convenient patterning process of high-resolution electrode circuits with a high degree of freedom even on a deformable platform.

Graphene RF and microwave passive components such as coplanar waveguide transmission lines, open/short-circuited resonators and wideband antenna on paper substrate were designed, screen printed and characterized in this work. The experimental results demonstrate that the screen printed graphene passive components can be used for RF signal transmitting, processing and radiating/receiving; revealing that graphene ink can be a low cost alternative to much more expensive metal nanoparticle inks, such as silver nanoparticle ink. The screen printed graphene is processed at low temperature so that it is compatible with heat-sensitive flexible materials like papers, PTFE (Polytetrafluoroethylene) and textiles. The screen printed graphene passive components reported here are of high conductivity, high flexibility, light weight and low cost, making them ideal candidate for low cost wearable electronics. This work makes it prospective to manufacture RF and microwave passive components in mass production by screen printing in much lower cost to any other known techniques.

Organic materials have played significant role in advancing sensor & display technologies for the past couple of years. Reliability and protection of various electronic components that are used in aircraft, artificial satellites and spacecraft for communications, navigation and the display and management of multiple systems are becoming more challenging due to their long-term performance requirements. In the recent years, organic polymers, particularly those deposited through vapor phase polymerization, have found an increasing role in the fabrication of display devices (including LED, OLED and FOLED), sensors, MEMS and optical windows and enhancing their overall reliability. Para-xylylene family of vapor phase polymers, particularly fluorinated Parylene (Parylene HT) offers unique characteristics for sensor, optical windows and display applications that are not available by other polymeric materials. This presentation describes a new development in the area of Parylenes and its role to advance the effectiveness of various types of LEDs, sensors, optical windows and display electronics. In addition, it highlights some characteristics for protection of various LEDs, sensors and their packaging components from solvent, gasoline, corrosive vapors, moisture and other harsh environmental effects including high temperature environments.

The manufacture and properties of polyaniline nano-films prepared through vapor-phase polymerization

Composite porous supercapacitor electrodes were prepared by growing poly(3,4-ethylenedioxythiophene) (PEDOT) on graphite nanoplatelet- or graphene nanoplatelet-deposited open-cell polyurethane (PU) sponges via a vapor phase polymerization (VPP) method. The resulting composite supercapacitor electrodes exhibited great capacitive performance, with PEDOT acting as both the conductive binder and the active material. The chemical composition was characterized by Raman spectroscopy and the surface morphology was characterized by scanning electron microscopy (SEM). Cyclic voltammetry (CV), charge-discharge (CD) tests and electrochemical impedance spectroscopy were utilized to study the electrical performance of the composite electrodes produced in symmetrically configured supercapacitor cells. The carbon material deposited on PU substrates and the polymerization temperature of PEDOT affected significantly the PEDOT morphology and the electrical properties of the resulting composite sponges. The highest areal specific capacitance 798.2 mF cm−2 was obtained with the composite sponge fabricated by VPP of PEDOT at 110 °C with graphene nanoplatelet-deposited PU sponge substrate. The capacitance retention of this composite electrode was 101.0% after 10,000 charging–discharging cycles. The high flexibility, high areal specific capacitance, excellent long-term cycling stability and low cost make these composite sponges promising electrode materials for supercapacitors.

An all polymer piezo/pyroelectric device was fabricated using β phase poly(vinylidene fluoride) (PVDF) as the active material and vapor phase polymerized (VPP) poly(3,4-ethylenedioxythiphene) (PEDOT) as the flexible electrode overlay material. Inherent problems usually associated with coating polymeric electrodes onto the low surface energy PVDF were overcome by air plasma treating the film in conjunction with utilizing the VPP technique to simultaneously synthesize and in situ deposit the PEDOT electrode. Strain measurements up to the breaking-strain of PVDF (approximately 35%) indicated that the change in R/Ro was significantly smaller for the PEDOT based electrodes compared to the platinum electrode. Plasma treatment of the PVDF film increased the level of surface oxygenated carbon species that contributed to increased surface energy, as confirmed by confirmed by contact angle measurement. The enhanced adhesion between the two polymers layers contributed to a significant increase in the measured piezoelectric output voltage from 0.2 to 0.5 V for the same strain conditions. Pyroelectric voltage outputs were obtained by placing the film onto and off of a hotplate, for temperatures up to 50 °C above ambient. Finally, as a proof of concept, a simple energy harvesting device (plastic tube with slots for mounting multiple piezo/pyro films) was fabricated. The device was able to generate a usable level of peak output current (>3.5 μA) from human inhalation and exhalation "waste energy".

Ladder-type structures can impart exceptional stability to polymeric electronic materials. This article introduces a new class of conductive polymers featuring a fully ladder-type backbone. A judicious molecular design strategy enables the synthesis of a low-defect ladder polymer, which can be efficiently oxidized and acid-doped to achieve its conductive state. The structural elucidation of this polymer and the characterization of its open-shell nature are facilitated with the assistance of studies on small molecular models. An autonomous robotic system is used to optimize the conductivity of the polymer thin film, achieving over 7 mS cm-1. Impressively, this polymer demonstrates unparalleled stability in strong acid and under harsh UV-irradiation, significantly surpassing commercial benchmarks like PEDOT:PSS and polyaniline. Moreover, it displays superior durability across numerous redox cycles as the active material in an electrochromic device and as the pseudocapacitive material in a supercapacitor device. This work provides structural design guidance for durable conductive polymers for long-term device operation.

In the development of flexible smart electronics, fabricating electrodes with optimized architectures to achieve superior electrochemical performance remains a significant challenge. This study presents a two-step synthesis and characterization of a polypyrrole (PPy)-MnO2/carbon cloth (CC) nanocomposite. The MnO2/CC substrate was first prepared via the hydrothermal method, followed by uniform PPy coating through vapor-phase polymerization in the presence of an oxidizing agent. Electrochemical measurements revealed substantial enhancement in performance, with the specific capacitance increasing from 123.1 mF/cm2 for the MnO2/CC composite to 324.5 mF/cm2 for the PPy/MnO2/CC composite at a current density of 2.5 mA/cm2. This remarkable improvement can be attributed to the synergistic effects between the conductive PPy polymer and MnO2/CC substrate and the formation of additional ion transport channels facilitated by the PPy coating. This work provides valuable insights for designing high-performance electrode materials and advances the development of composite-based energy storage devices.

A 1.8 MeV He-beam from a Van de Graaff accelerator has been used to demonstrate that back-scattering techniques can be usefully applied to study certain problems related to the interaction between coatings and paper substrates and between printing inks and coated or uncoated paper or plastic substrates. In particular, information on distribution profiles of various components can be obtained. The technique and some of its practical aspects are briefly described.

Fadable ink for time–temperature control of food freshness: Novel new time–temperature indicator