Paper-based Electronics Research Articles

Chitosan-assisted buffer layer incorporated with hydroxypropyl methylcellulose-coated silver nanowires for paper-based sensors

Fabricating flexible sensors on paper is intriguing. Here, we exploited chitosan as a buffer layer to facilitate the fabrication of silver nanowire (AgNW) networks and flexible devices on commercial paper. We found that the AgNW networks exhibited uniform distribution, smooth surface, and strong adhesion. The enhanced adhesion of AgNWs was attributed to the intermolecular hydrogen bonding between chitosan and hydroxypropyl methylcellulose (HPMC), which can be tailored by tuning the pH of the chitosan aqueous solution. This facile fabrication method utilizing biodegradable polymers and cost-effective AgNW ink holds great promise for portable, wearable, and disposable paper-based electronics.

Cu-based composite inks of a self-reductive Cu complex with Cu flakes for the production of conductive Cu films on cellulose paper

Paper-based electronics have been attracting significant attention because of their inexpensive, renewable, and eco-friendly substrates. In this study, Cu-based composite inks composed of a copper-based metal-organic decomposition (MOD) ink and Cu flakes were prepared as precursors to obtain conductive Cu films on untreated cellulose paper. Copper-based MOD inks have not been explored for the production of conductive Cu films on cellulose paper because the properties of the paper, such as high porosity, high permeability, and surface roughness, are not favorable to obtain continuous conductive Cu films. However, using our method, we have obtained Cu films on paper with resistivities that are ∼10 times lower than those of films on polyimide or glass substrates. Importantly, the Cu films on paper exhibited better mechanical resistance than those on a polyimide substrate, without any pre-treatment of the paper surface.

Study of the correlation between sensing performance and surface morphology of inkjet-printed aqueous graphene-based chemiresistors for NO2 detection.

The extremely high sensitivity to the external environment and the high specific surface area, as well as the absence of bulk phenomena that could interfere with the response signal, make graphene highly attractive for the applications in the field of sensing. Among the various methods for producing graphene over large areas, liquid phase exfoliation (LPE) appears to be very promising, especially if combined with inkjet printing (IJP), which offers several advantages, including the selective and controlled deposition of small ink volumes and the versatility of the exploitable inks and substrates. Herein we present a feasibility study of chemiresistive gas sensors inkjet-printed onto paper substrates, in which a LPE graphene suspension dispersed in a water/isopropanol (H2O/IPA) mixture is used as sensing ink. The device performances, in terms of relative conductance variations, upon exposure to NO2 at standard ambient temperature and pressure, are analysed. In addition, we examine the effect of the substrate morphology and, more specifically, of the ink/substrate interaction on the device performances, by comparing the response of different chemiresistors fabricated by dispensing the same suspension also onto Al2O3 and Si/SiO2 substrates and carrying out a supportive atomic force microscopy analysis. The results prove the possibility to produce sensor devices by means of a wholly environmentally friendly, low-cost process that meets the requests coming from the increasing field of paper-based electronics and paving the way towards a flexible, green-by-design mass production.

Simple transfer of Ag nanowires by dry film photoresist for paper-based flexible electronics

In this study, the facile dry transfer of silver nanowires (AgNWs) to a paper substrate using a dry film photoresist (DFR) was explored. No-primer-treated polyethylene terephthalate (NP-PET) with low adhesion strength and DFR were used as the carrier substrate and transfer medium for the AgNWs, respectively. Because of the lower adhesion of DFR to NP-PET than to paper, the DFR-coated AgNWs on NP-PET were successfully transferred to the paper substrate using simple hot pressing. The fabricated AgNW/DFR/paper electrodes were highly reliable without degradation in their electrical conductivity after 1000 bending cycles, and their feasibility as flexible electrodes was confirmed by demonstrating the operation of a light-emitting diode and flexible thin-film heater.

Flexible Paper Photodetectors Based on 2D BN Nanosheets

The market for printed and flexible electronics, key attributes for internet of things, is estimated to reach $45 billion by 2016 and paper-based electronics shows great potential to meet this increasing demand due to its popularity, flexibility, low cost, mass productivity, disposability, and ease of processing. However, conventional flexible devices made of paper and plastic substrates are expected to have thermal issues due to their poor thermal conductivity. In this work, we demonstrated flexible solar-blind deep-ultraviolet (DUV) sensors based on 2D boron nitride nanosheets (BNNSs) composited paper with good detectivity (up to 8.05 × 1010 cm Hz1/2/W), fast recovery time (down to 0.393 s), great thermal stability (146 W/m K, 3-order-of-magnitude larger than conventional flexible substrates), high working temperature (up to 200 oC), excellent flexibility and bending durability (showing repeatable ON/OFF switching during 200-time bending cycles). This shows great potential to be a key component to solve thermal problems and fully activate flexible electronics for meeting the demand of internet of things.

Enabling Mobile Health

The need for new, easy-to-use, home and decentralised diagnostics is now greater than ever and it is rapidly becoming apparent that biosensors can contribute substantially to reducing healthcare costs. New thinking is crucial to finding effective solutions that deliver the high quality of life rightly demanded by our ever ageing population while leveraging technology to deliver this in a cost-effective manner. Several key drivers are catalysing change. Personalised medicine recognises that every individual is different and needs a tailor-made health package; these differences can only be identified with an appropriate suite of diagnostics. Individuals are increasing recognising that data about their bodies should be owned by them and that they should have the choice to use and supplement this information. This generates consumer choice and drives evidence-based payment, where the success of outcomes needs to be measured. Focus on the individual and their needs drives decentralisation and the possible radical restructuring of how we deliver health management. We already see “health rooms” in pharmacies, but the next step will be health rooms in your home, in your pocket or on your wrist. These advances are underpinned by technologies facilitating mobility and data processing, but at the core are rapid, convenient and easy ways to measure our body chemistries at the genomic, proteomic and metabolomic levels. This presentation will focus on meeting these challenges using paper-based electronics, polymers and integrated electrochemical systems to deliver inexpensive instruments for a wide range of bioanalytical applications. Approaches will be illustrated by multi-parametric monitoring for the management of diabetes, chronic kidney disease and stress, reversible and label-free affinity sensors for cancer markers and heart disease, aptasensors for pathogens and cancer cells, and robust microbial-differentiation arrays. Further development will result in cost reduction and a diversity of formats such as point-of-care tests, smart packaging, telemetric strips and print-on-demand analytical devices.

Development of Paper-based Electronics and Sensors Fabricated by Printing

Development of Paper-based Electronics and Sensors Fabricated by Printing

Natural Materials Assembled, Biodegradable, and Transparent Paper-Based Electret Nanogenerator.

Developing eco-friendly and low-cost electronics is an effective strategy to address the electronic waste issue. In this study, transparent cellulose nanopaper (T-paper) and polylactic acid (PLA) electret were used to construct a biodegradable and transparent paper-based electret nanogenerator. The nanogenerator could be assembled with paper products to form a self-powered smart packaging system without impairing the appearance, due to the high transparency and desirable output performance. Furthermore, the self-degradation property in the natural soil of the nanogenerator is demonstrated, indicating that the nanogenerator is recycled and will not pollute the environment. We anticipate that this study will provide new insights to develop eco-friendly power source and paper-based electronics.

Facial fabrication of paper-based flexible electronics with flash foam stamp lithography

Paper-based flexible electronics/circuit have a bright potential in displays, transistor and sensors due to low cost and disposability. Here we presented a facile microfabrication method for paper-based flexible electronics with flash foam stamp lithography (FFSL), which can be implemented in resource-limited laboratory. Only two steps are needed. Firstly, negative patterns of circuit are stamped on the paper with polydimethylsiloxane (PDMS) ink to form hydrophobic barriers after PDMS is solidified. Then the patterned paper is immersed in the conductive ink to absorb ink and acquire circuits. In this paper we present foldable, waterproof and multi-layer paper-based flexible electronics can be easily fabricated. Also as FFSL can be also directly used in fabrication of microfluidic paper-based analytical devices (μPADs), this method has a promising potential in fabricating electrodes of μPADs.

In-situ synthesized polypyrrole-cellulose conductive networks for potential-tunable foldable power paper

Flexible electronics with features of simple, low-cost, lightweight, recyclable, easily operable, and disposable are particularly desirable. Herein, a flexible fully-integrated self-powered system on paper was demonstrated by incorporating addressable paper circuit switch into potential-tunable foldable power paper. In which the electrode material as well as conducting interconnections, p-toluenesulfonic acid (p-TSA) doped polypyrrole embedded in-between the cellulose fibers (p-TSA-PPy/cellulose) were obtained by combining in-situ chemical oxidative polymerization with paper microfluidic technique. In such unique integrated configuration, the utilization of p-TSA-PPy/cellulose network not only dramatically enhanced the horizontal electrical conductivity, but also conquered the issue of vertical electroconductivity, allowing for the top-channel-bottom conductive interconnections. As a proof-of-concept, an all-paper microfluidic analytical platform that integrated paper-based electrochemiluminescence strategy and proposed power paper was constructed with comparable performance. This work greatly improves the understandings of all-paper-based self-powered systems, and presents the significant potential applications of paper-based flexible electronics.

Recent Advancements in Functionalized Paper-Based Electronics.

Building electronic devices on ubiquitous paper substrates has recently drawn extensive attention due to its light weight, low cost, environmental friendliness, and ease of fabrication. Recently, a myriad of advancements have been made to improve the performance of paper electronics for various applications, such as basic electronic components, energy storage devices, generators, antennas, and electronic circuits. This review aims to summarize this progress and discuss different perspectives of paper electronics as well as the remaining challenges yet to be overcome in this field. Other aspects included in this review are the fundamental characteristics of paper, modification of paper with functional materials, and various methods for device fabrication.

Polymer Light Emitting Diodes Powered via Paper-Mounted Electronics

We have interfaced an array of polymer light emitting diodes (OLEDs) fabricated onto a glass substrate to a sheet of paper via a pressure sensitive conducting adhesive. By screen printing a series of capacitive touch pads and connecting tracks onto paper using a low-cost conductive graphite ink, we are able to drive individual pixels in the OLED array via CMOS-based electronics that are also attached to the paper. Three AA batteries are used to power the CMOS electronics, touch pads and the OLED array, with pixels in the array operating at a brightness of up to 210 cd/m2. The work highlights a practical interface between plastic- and paper-based electronics.

Dispensing of high concentration Ag nano-particles ink for ultra-low resistivity paper-based writing electronics.

Paper-based writing electronics has received a lot of interest recently due to its potential applications in flexible electronics. To obtain ultra-low resistivity paper-based writing electronics, we developed a kind of ink with high concentration of Ag Nano-particles (up to 80 wt%), as well as a related dispensing writing system consisting an air compressor machine and a dispenser. Additionally, we also demonstrated the writability and practical application of our proposed ink and writing system. Based on the study on the effect of sintering time and pressure, we found the optimal sintering time and pressure to obtain high quality Ag NPs wires. The electrical conductivity of nano-silver paper-based electronics has been tested using the calculated resistivity. After hot-pressure sintering at 120 °C, 25 MPa pressure for 20 minutes, the resistivity of silver NPs conductive tracks was 3.92 × 10−8 (Ωm), only 2.45 times of bulk silver. The mechanical flexibility of nano-silver paper-based electronics also has been tested. After 1000 bending cycles, the resistivity slightly increased from the initial 4.01 × 10−8 to 5.08 × 10−8 (Ωm). With this proposed ink preparation and writing system, a kind of paper-based writing electronics with ultra-low resistivity and good mechanical flexibility was achieved.

3D nanostructured inkjet printed graphene via UV-pulsed laser irradiation enables paper-based electronics and electrochemical devices.

Emerging research on printed and flexible graphene-based electronics is beginning to show tremendous promise for a wide variety of fields including wearable sensors and thin film transistors. However, post-print annealing/reduction processes that are necessary to increase the electrical conductivity of the printed graphene degrade sensitive substrates (e.g., paper) and are whole substrate processes that are unable to selectively anneal/reduce only the printed graphene-leaving sensitive device components exposed to damaging heat or chemicals. Herein a pulsed laser process is introduced that can selectively irradiate inkjet printed reduced graphene oxide (RGO) and subsequently improve the electrical conductivity (Rsheet∼0.7 kΩ□(-1)) of printed graphene above previously published reports. Furthermore, the laser process is capable of developing 3D petal-like graphene nanostructures from 2D planar printed graphene. These visible morphological changes display favorable electrochemical sensing characteristics-ferricyanide cyclic voltammetry with a redox peak separation (ΔEp) ≈ 0.7 V as well as hydrogen peroxide (H2O2) amperometry with a sensitivity of 3.32 μA mM(-1) and a response time of <5 s. Thus this work paves the way for not only paper-based electronics with graphene circuits, it enables the creation of low-cost and disposable graphene-based electrochemical electrodes for myriad applications including sensors, biosensors, fuel cells, and theranostic devices.

Flexible and printable paper-based strain sensors for wearable and large-area green electronics.

Paper-based (PB) green electronics is an emerging and potentially game-changing technology due to ease of recycling/disposal, the economics of manufacture and the applicability to flexible electronics. Herein, new-type printable PB strain sensors (PPBSSs) from graphite glue (graphite powder and methylcellulose) have been fabricated. The graphite glue is exposed to thermal annealing to produce surface micro/nano cracks, which are very sensitive to compressive or tensile strain. The devices exhibit a gauge factor of 804.9, response time of 19.6 ms and strain resolution of 0.038%, all performance indicators attaining and even surpassing most of the recently reported strain sensors. Due to the distinctive sensing properties, flexibility and robustness, the PPBSSs are suitable for monitoring of diverse conditions such as structural strain, vibrational motion, human muscular movements and visual control.

Controllable Hydrothermal Growth of ZnO Nanowires on Cellulose Paper for Flexible Sensors and Electronics

Seamless integration of functional nanomaterials on paper can boost the functionality of paper-based flexible sensors and electronics. In this paper, we report the systematic study of a low-cost hydrothermal process for growing zinc oxide nanowires (ZnO NWs) on cellulose paper substrates. To control the competition between homogeneous and heterogeneous nucleation and obtain ZnO NWs with superior morphology and high growth efficiency, we tune the critical growth parameters including temperature, assistant chemicals, and seeding layer. We experimentally confirm the necessity of ammonium hydroxide as assistant chemical in the growth solution, and achieve a condition that generates the highest weight growth percentage of 40% in the tested range. We quantify the weight growth percentage of ZnO NWs over growth time, measure the electrical resistance of the ZnO-NW paper, and eventually establish an experimental guideline for preparing ZnO-NW paper with desired electrical property. To demonstrate potential applications of the ZnO-NW paper, we use the obtained ZnO-NW paper for sensing of ultraviolet light and mechanical touch. This paper provides experimental insights into hydrothermal growth of ZnO NWs on paper, and could further inspire novel utilization of ZnO-NW paper for flexible sensors and electronics.

Flexible, Foldable and Multi-Functional Paper-Based Electronics

Great advances have been made in developing cheap, simple, multi-functional and energy-saving fabrication processes for flexible electronics.1 Paper, as a flexible, foldable, cost-efficient and mass productive substrate, has shown diverse applications for flexible electronics to meet such demand. Recently, we have successfully demonstrated the first nonvolatile resistive memory using paper as substrates by means of all-printing techniques.2 Moreover, we also implemented the algorithm of Origami art into the device design for the flexible optoelectronics, such as photodetector and nanogenerator, taking advantage of the foldability and adaptability of paper substrate. In particular, paper origami triboelectric nanogenerators (TENGs) using paper as the starting material, with high degree of flexibility, light weight, low cost, and recyclability is presented.3 We believe that these findings will pave a way for future energy harvesting and sensor design, especially for the development of green flexible electronics. Figure 1

Low-Cost, High-Efficiency Conductive Papers Fabricated Using Multi-Walled Carbon Nanotubes, Carbon Blacks and Polyvinyl Alcohol as Conducting Agents

Paper-based electronics or energy storage devices are emerging as next-generation technology. However, conducting agents for paper electrodes are prohibitively expensive at present. In this work, we demonstrate a facile and cost-effective way of converting sheets of commercial papers into high-performance conductive electrodes for supercapacitors. Multi-walled carbon nanotubes (CNTs), carbon blacks (CBs), and polyvinyl alcohol were successfully employed to fabricate conductive, flexible, bendable, disposable and foldable paper electrodes. The CNTs showed higher mass-specific capacitance (219 Fg−1), area-specific capacitance (9.8 mFcm−2), and energy density (30 Wh kg−1). Carbon blacks also demonstrated significantly large mass-specific capacitance (92 Fg−1) and area-specific capacitance (4.4 mFcm−2). This work is the first report on carbon-blacks-based paper electrodes of supercapacitors. Our method could provide a scalable way to realize paper-based electrode materials, which could find applications in next generation wearable devices.

Paper-supported nanostructured ultrathin gold film electrodes – Characterization and functionalization

Ultrathin gold films (UTGFs) were fabricated on a nanostructured latex-coated paper substrate by physical vapour deposition (PVD) with the aim to provide low-cost and flexible conductive electrodes in paper-based electronics. Morphological, electric and optical properties of UTGFs were dependent on the deposited film thickness. In addition, UTGFs were functionalized with insulating and hydrophobic 1-octadecanethiol self-assembled monolayer and inkjet-printed conductive and hydrophilic poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT–PSS) layer and their electrochemical properties were examined. Results showed that sufficient mechanical stability and adhesion of UTGFs deposited on latex-coated paper was achieved without the need on any additional adhesive layers, enabling a more robust fabrication process of the electrodes. UTGF electrodes tolerated extensive bending without adverse effects and conductivity comparable to the bulk gold was obtained already with the film thickness of 6nm. Although not been fabricated with the high-throughput method like printing, a very low material consumption (∼12μg/cm2) together with a high conductivity (resistivity<3×10−6Ωcm) makes the UTGFs electrodes potential candidates low-cost components in flexible electronics. In addition, the excellent stability of the UTGF electrodes in electrochemical experiments enables their application in the development of paper-based electrochemical platforms, e.g. for biosensing purposes.

Paper-based piezoelectric touch pads with hydrothermally grown zinc oxide nanowires.

This paper describes a new type of paper-based piezoelectric touch pad integrating zinc oxide nanowires (ZnO NWs), which can serve as user interfaces in paper-based electronics. The sensing functionality of these touch pads is enabled by the piezoelectric property of ZnO NWs grown on paper using a simple, cost-efficient hydrothermal method. A piece of ZnO-NW paper with two screen-printed silver electrodes forms a touch button, and touch-induced electric charges from the button are converted into a voltage output using a charge amplifier circuit. A touch pad consisting of an array of buttons can be readily integrated into paper-based electronic devices, allowing user input of information for various purposes such as programming, identification checking, and gaming. This novel design features ease of fabrication, low cost, ultrathin structure, and good compatibility with techniques in printed electronics, and further enriches the available technologies of paper-based electronics.