Composite Ink Research Articles

Real-time monitoring of graphene oxide reduction in acrylic printable composite inks

This work reports the electrical characterization of a water-based graphene oxide/acrylic composite material, which was directly inkjet printed to fabricate dissipative patterns. The graphene oxide filler, which is strongly hydrophilic due to its heavily oxygenated surface and can be readily dispersed in water, was reduced by UV irradiation during photo-curing of the polymeric matrix. The concurrent polymerization of the acrylic matrix and reduction of graphene oxide filler was demonstrated by real-time resistance measurements during UV light irradiation. The presence of graphene filler allowed decreasing the resistance of the pure polymeric matrix by nearly five orders of magnitude. This was explained by the fact that clusters of reduced graphene oxide inside the polymer matrix act as preferential pathways for the mobility of charge carriers, thus leading to an overall decrease of the material’s resistance.

Synthesis of sub-10-nm Sn nanoparticles from Sn(II) 2-ethylhexanoate by a modified polyol process and preparation of Ag[sbnd]Sn film by melting of the Sn nanoparticles

Ultrafine Sn nanoparticles (NPs) (diameter<10nm) exhibiting a remarkable depression in their melting point were synthesized at room temperature by a modified polyol process. For the synthesis, low-grade Sn(II) 2-ethylhexanoate and sodium borohydride were used as the precursor and reducing agent in a diethylene glycol medium. Further, polyvinyl pyrrolidone was used as a capping agent during the synthesis. The synthesized crystalline Sn NPs showed an average diameter of 7.98nm and an extremely low melting point of 128°C. To test the applicability of the synthesized ultrafine Sn NPs to practical systems, an Ag-based composite ink containing the Sn NPs was prepared. The ink was easily sintered through local liquid-phase sintering by melting of the ultrafine Sn NPs added as a metal binder. Therefore, despite the low-temperature (170°C) sintering with a short duration (~15min), the composite ink exhibited excellent sheet resistance.

Personal electronics printing via tapping mode composite liquid metal ink delivery and adhesion mechanism

Printed electronics is becoming increasingly important in a variety of newly emerging areas. However, restricted to the rather limited conductive inks and available printing strategies, the current electronics manufacture is usually confined to industry level. Here, we show a highly cost-effective and entirely automatic printing way towards personal electronics making, through introducing a tapping-mode composite fluid delivery system. Fundamental mechanisms regarding the reliable printing, transfer and adhesion of the liquid metal inks on the substrate were disclosed through systematic theoretical interpretation and experimental measurements. With this liquid metal printer, a series of representative electronic patterns spanning from single wires to desired complex configurations such as integrated circuit (IC), printed-circuits-on-board (PCB), electronic paintings, or more do-it-yourself (DIY) devices, were demonstrated to be printed out with high precision in a moment. And the total machine cost already reached personally affordable price. This is hard to achieve by a conventional PCB technology which generally takes long time and is material, water and energy consuming, while the existing printed electronics is still far away from the real direct printing goal. The present work opens the way for large scale personal electronics manufacture and is expected to generate important value for the coming society.

Fabrication and characterization of solution-processed carbon nanotube supercapacitors

ABSTRACTWe report the fabrication and characterization of supercapacitors prepared on a flexible substrate using a printable, high-viscosity carbon nanotube (CNT) ink. The CNT-hemicellulose composite ink was prepared using ultrasonication and applied on the substrate with a doctor blade. Aqueous sodium chloride was used as electrolyte. The capacitance of the supercapacitors was 16 mF for a device size of 2 cm2. The measurements were carried out in accordance to an international standard for electric double layer capacitors.

Single-walled carbon nanotube composite inks for printed gas sensors: enhanced detection of NO2, NH3, EtOH and acetone

SWNT–metal oxide composites for improvement of response and selectivity in gas sensors.

Fabrication, characterization and screen printing of conductive ink based on carbon@Ag core–shell nanoparticles

The large-scale synthesis and characterization of carbon–core/Ag–shell (C@Ag) nanoparticles by the successive reduction of silver ammonia are described. The resultant C@Ag nanoparticles had a mean core diameter of 360nm and a controllable shell thickness from 10 to 40nm by simple adjustments of repeat coating times. Various analysis techniques confirmed that the carbon cores were fully covered by Ag nanoshells. The results also show that C/Ag composite nanomaterials-based conductive inks, which can be easily produced on a large scale and possess outstanding electronic properties, have great potential for the convenient fabrication of flexible and low-cost carbon-based electronic devices and replace the traditional pure silver paste, by using a simple screen printing technique.

Sensitive and selective dopamine determination in human serum with inkjet printed Nafion/MWCNT chips

An inkjet printed Nafion/MWCNT chip was developed for rapid dopamine determination in undiluted human serum. A well-dispersed Nafion/MWCNT composite ink was investigated with homogeneous double layers which increased the efficiency of dopamine detection, where direct electron exchange was achieved, producing a measurable current change at the underlying sensor electrode. This platform successfully demonstrated direct detection of DA concentrations (0.1μM to 10μM, R=0.999) in real human serum samples using DPV and amperometry methods. This direct measurement of DA in serum samples without pretreatment and dilution is reported for the first time in a Nafion/MWCNT system.

Composite inks of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)/silver nanoparticles and electric/optical properties of inkjet-printed thin films

Poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate)/silver nanoparticles composite inks have been prepared through in situ synthesis and ultrasonic dispersion. The developed inks were proved to be suitable for various inkjet printing trials to deposit the thin films which were subsequently characterized to assess their electric and optical properties. The results have indicated that the dedoping of PSS from PEDOT during the in situ synthesis can be detrimental to the conductivity of the deposited composite films. However, the addition of silver nanoparticles to pristine PEDOT:PSS has significantly enhanced the conductivity of the thin films, with an inevitable loss in transparency. The various factors that can influence the properties of the thin films have also been analyzed and discussed. This study provides an insight into the effect of silver nanoparticles on PEDOT:PSS thin films deposited using inkjet printing process, and their properties due to the methods of ink formulation.

An alternative route towards low-cost Cu2ZnSnS4 thin film solar cells

A non-vacuum and low-cost route to fabrication of Cu2ZnSnS4 (CZTS) thin film as absorber layer for thin film solar cell is demonstrated. The process involves synthesis of Cu–Zn–Sn composite oxide nanoparticles, preparation of composite oxide ink, deposition of composite oxide thin film and subsequent sulfurization treatment. Cu–Zn–Sn composite oxide nanoparticles with proper composition and particle size can be obtained by controlling the chemical co-precipitation conditions. The effects of sulfurization temperature on the compositional, structural, morphological, optical and electrical properties of the CZTS thin films were investigated. XRD, Raman and X-ray photoelectron spectroscopy analyses confirmed the formation of CZTS phase after sulfurization. The prepared CZTS thin films exhibit porous morphology and an optical band gap about 1.35eV. The solar cells fabricated with the CZTS thin film sulfurized at 550°C showed a conversion efficiency of 1.22%.

Free-standing nanocomposites with high conductivity and extensibility

The prospect of electronic circuits that are stretchable and bendable promises tantalizing applications such as skin-like electronics, roll-up displays, conformable sensors and actuators, and lightweight solar cells. The preparation of highly conductive and highly extensible materials remains a challenge for mass production applications, such as free-standing films or printable composite inks. Here we present a nanocomposite material consisting of carbon nanotubes, ionic liquid, silver nanoparticles, and polystyrene–polyisoprene–polystyrene having a high electrical conductivity of 3700 S cm−1 that can be stretched to 288% without permanent damage. The material is prepared as a concentrated dispersion suitable for simple processing into free-standing films. For the unstrained state, the measured thermal conductivity for the electronically conducting elastomeric nanoparticle film is relatively high and shows a non-metallic temperature dependence consistent with phonon transport, while the temperature dependence of electrical resistivity is metallic. We connect an electric fan to a DC power supply using the films to demonstrate their utility as an elastomeric electronic interconnect. The huge strain sensitivity and the very low temperature coefficient of resistivity suggest their applicability as strain sensors, including those that operate directly to control motors and other devices.

Assembled graphene oxide and single-walled carbon nanotube ink for stable supercapacitors

Abstract

Inkjet Printing of Conjugated Polymer Precursors on Paper Substrates for Colorimetric Sensing and Flexible Electrothermochromic Display

Inkjet-printable aqueous suspensions of conjugated polymer precursors are developed for fabrication of patterned color images on paper substrates. Printing of a diacetylene (DA)-surfactant composite ink on unmodified paper and photopaper, as well as on a banknote, enables generation of latent images that are transformed to blue-colored polydiacetylene (PDA) structures by UV irradiation. Both irreversible and reversible thermochromism with the PDA printed images are demonstrated and applied to flexible and disposable sensors and to displays.

Thick-film acoustic emission sensors for use in structurally integrated condition- monitoring applications

Monitoring the condition of complex engineering structures is an important aspect of modern engineering, eliminating unnecessary work and enabling planned maintenance, preventing failure. Acoustic emissions (AE) testing is one method of implementing continuous nondestructive structural health monitoring. A novel thick-film (17.6 μm) AE sensor is presented. Lead zirconate titanate thick films were fabricated using a powder/sol composite ink deposition technique and mechanically patterned to form a discrete thick-film piezoelectric AE sensor. The thick-film sensor was benchmarked against a commercial AE device and was found to exhibit comparable responses to simulated acoustic emissions.

Development of Pr 0.58Sr 0.4Fe 0.8Co 0.2O 3 − δ –GDC composite cathode for solid oxide fuel cell (SOFC) application

Improvement of performances of SOFCs/SOECs demands the development of novel materials for its commercially viability and practicability in operations. For air electrode applications novel materials like cobalt based compounds, which offer both ionic and electronic conductivity (MIECs), to achieve high performance are very promising. Among these Pr 1 − x Sr xFe 1 − y Co yO 3 − δ (PSCF) seems to be very suitable material for oxygen electrode in SOFCs. In the present study, we have chosen Pr 0.58Sr 0.4Fe 0.8Co 0.2O 3 − δ as the composition of the PSCF material. To overcome the high thermal expansion coefficient of this material with the electrolyte, 10 mol% Gd doped ceria (GDC) is used as the composite material. Chemical compatibility between these two materials was ascertained by the XRD analysis of the calcined composite mixture. Composites of PSCF and GDC with different weight ratio were made and symmetric cells were fabricated using screen printing of the composite ink. Based on the polarisation resistance measurements, PSCF50–GDC50 composite was found to be suitable. From the dilatometric shrinkage curve of the composite pellet, a range of the possible sintering temperatures was identified. From the microstructural observations and the polarisation resistance measurement of the symmetric cells at 800 °C under air, 1100 °C was chosen as the most suitable sintering temperature. Optimization of the thickness of the screen printed electrode was carried out. From the symmetric cell measurements, the polarisation resistance of the electrodes having coating thickness from 8 to 9 μm, has shown the minimum polarisation resistance of 0.12 Ω cm² at 800 °C in air atmosphere. Very low polarisation resistance of PSCF, suitable physical stability and microstructure indicates that this is a promising material for air electrode applications in improving the performance of SOFCs and SOECs.

Inkjet Printing of Multi-Walled Carbon Nanotube/Polymer Composite Thin Film for Interconnection

In this paper, multi-walled carbon nanotube (MWCNT) ink was selectively patterned by inkjet printing on substrates to form conductive traces and electrodes for interconnection application. MWCNT was firstly functionalized using concentrated acid and dispersed in deionized water to form a colloidal solution. Various concentrations of MWCNT were formulated to test the stability of the solution. The printability of the MWCNT ink was examined against printing temperature, ink concentration and ink droplet pitch. Rheological properties of the ink were determined by rheometer and sessile drop method. The electrical conductivity of the MWCNT pattern was measured against multiple printing of MWCNT on the same pattern (up to 10 layers). While single layer printing pattern exhibited highest resistance, the CNT entangled together and formed a random network with more printed layers has higher conductivity. The electrical properties of the printed film was compared to a composite ink of CNT and conducting polymer (CNT ink was mixed with conductive polymer solution, Poly(3,4-ethylenedioxythiophene)-Poly(styrenesulfonate) (PEDOT:PSS)). Scanning electron microscopy (SEM) was used to observe the surface structure and atomic force microscopy (AFM) was used to study the morphology of the printed film under different conditions.

Ink‐Jet Printing: A Versatile Method for Multilayer Solid Oxide Fuel Cells Fabrication

The potential of ink‐jet printing for fabrication of components for solid oxide fuel cells has been explored. An anode interlayer, consisting of a composite of NiO and yttria‐stabilized zirconia (YSZ), and an electrolyte layer, YSZ (8 mol%), were ink‐jet printed on a tape cast anode support, 55 wt% NiO–45 wt% YSZ (8 mol%). Scanning electron microscopy of the printed layers sintered at 1400°C revealed a dense electrolyte layer measuring 10–12 μm in thickness. Single cells using these printed layers and strontium‐doped lanthanum manganate (LSM, La0.8Sr0.2MnO3)‐based pasted cathodes were assessed by DC polarization and AC complex impedance methods. The cells exhibited a stable open circuit voltage of 1.1 V around 800°C, in a hydrogen atmosphere. A maximum power density of 500 m·(W·cm)−2 was achieved at 850°C for a typical cell with the electrolyte and anode interlayer cosintered at 1400°C. A composite cathode interlayer, LSM–YSZ, and a cathode current collection layer, LSM, were also ink‐jet printed and incorporated in single cells. However, cells with all components ink‐jet printed showed decreased performance. This pointed to critical issues in the composite cathode microstructure, which is controlled by the composite ink design/formulation and printing parameters that need to be addressed.

Patterning conductive PDMS nanocomposite in an elastomer using microcontact printing

This paper introduces a simple method of embedding conductive and flexible elastomer micropatterns into a bulk elastomer. Employing microcontact printing and cast molding techniques, patterns consisting of conductive poly(dimethylsiloxane) (PDMS) composites mixed with multi-walled carbon nanotubes (MWCNTs) are embedded into bulk PDMS to form all-elastomer devices. To pattern conductive composites, a micromachined printing mold is utilized to transfer composite ink from a spin-coated thin layer to another substrate. Distinct from previously reported approaches, the printing mold in this technique, once fabricated, can be repeatedly used to generate new patterns and therefore greatly simplifies the device fabrication process and improves its efficiency. Manufactured devices with embedded conductive patterns exhibit excellent mechanical flexibility. With characterization of printing reliability, electrical conductivity of the composites is also shown with different loading percentages of MWCNTs. Furthermore, a simple strain gauge was fabricated and tested to demonstrate the potential applications of embedded conductive patterns. Overall, this approach demonstrates feasibility to be a simple method to pattern conductive elastomers that work as electrodes or sensing probes in PDMS-based devices. With further development, this technology yields many potential applications in lab-on-a-chip systems.

Piezoelectric Inkjet Printing of Biomimetic Inks for Reactive Surfaces

Dendrimer printing: A composite dendrimer ink is developed and patterned onto gold, glass, or sapphire substrates using piezoelectric inkjet printing. Varying the spot spacing, the number of print cycles, and the reaction time with monosilicic acid (see image) provides a microenvironment with properties reminiscent of patterned silica on the cell wall of diatoms.

Micromoulding of lead zirconate titanate (PZT) structures for MEMS

Thick (>10 μm) ceramic structures for applications in micro-electromechanically systems are typically fabricated using screen printing techniques or by printing a continuous film and subsequently etching the structure. This work presents a thick film lift off technique to create high aspect ratio thick Lead Zirconate Titanate (PZT) features on silicon substrates. In this technique, a photoresist material is used to produce a mould, on a silicon substrate, and so define the shape of structures to be created. A composite sol gel ink (mixture of ceramic powder and sol) is then cast into the polymeric moulds and heat treated at low temperature (<250°C) to dry the ink. The use of these low temperatures means that the polymeric mould maintains its shape whilst still allowing the sol to be converted to an amorphous ceramic precursor. Subsequent deposition of further composite sol gel ink can then be used to increase the thickness of the features. The density of the structures can also be increased through the use of repeated sol infiltrations once the structure has been created. A final heat treatment is used to remove the polymeric moulds and crystallise the ceramic material.

Screen-printable sol–gel ceramic carbon composite pH sensor with a receptor zeolite

A screen-printable method is proposed to prepare a ceramic carbon composite sensor for pH determination. The pH-sensing membrane of the sensor is prepared by sol–gel, graphite powder and zeolite, in which zeolite is used as a receptor of proton. The fabrication of this ceramic carbon sensor includes three steps: preparing electrode slides, making a pH-sensing composite ink and screen-printing the ink on electrode slides. Optimum conditions for the ceramic carbon composite film are established, and characters of the pH electrode (stability, reproducibility, lifetime and conductivity) are examined comparing with glass pH electrodes. The Nernst response to pH of the sensor is in the range of pH 1–12 with a slope of 60 mV per pH. The sensor has been applied to pH measurements of samples and satisfactory results were obtained with R.S.D. of 0.18–1.25%.