Ink formulation, scalable applications and challenging perspectives of screen printing for emerging printed microelectronics

Screen printing is regarded as a highly competitive manufacture technology for scalable and fast fabrication of printed microelectronics, owing to its advanced merits of low-cost, facile operability and scalability.However, its large-scale application in printed microelectronics is still limited by screen printing functional ink. In this review, we summarize the recent advances of ink formation, typical scalable applications, and challenging perspectives of screen printing for emerging printed microelectronics. Firstly, we introduce the major mechanism of screen printing and the formation of different organic-and aqueous-based inks by various solvents and binders. Next, we review the most widely used applications of screen printing technique in micro-batteries, micro-supercapacitors and micro-sensors, demonstrative of wide applicability.Finally, the perspectives and future challenges in the sight of screen printing are briefly discussed.

Highly Conductive Fractal-structured Silver Particles for Preparing Flexible Printed Circuits via Screen Printing

Fractal-structured silver particles(FSSPs)are conductive materials with a micron-scale trunk and nanoscale branches,and are characterized with high electrical conductivity and high connectivity.In this study,FSSPs were added to an aqueous additive solution for synthesizing a conductive ink,which was used to prepare two types of printing electrodes via screen printing.The first type included two flexible printed electrodes(FPEs):an FPE on a polyethylene terephthalate(PET)film and an FPE on paper.The second one was a polydimethylsiloxane(PDMS)-embedded FPE.The PETbased FPE exhibited high electrochemical stability when its sheet resistance was 0.38Ω/sq for a 50%(w/w)content of FSSPs in the prepared conductive ink.Moreover,the embedded FPE demonstrated excellent mechanical properties and high chemical stability.In addition,the embedded structure was endowed with stretchability,which is important for different devices,such as flexible biomedical sensors and flexible electronics.

Enzyme Biosensor for Detection of Organophosphate Pesticide Residues Base on <i>Screen Printed Carbon Electrode</i>(SPCE)-Bovine Serum Albumin (BSA)

The maximum level of organophosphate pesticide residues in rice is 0.1 mg/kg and 0.5 mg/kg in vegetables. The control of pesticide residues in agricultural products required a method of analysis quickly and accurately. The research developed a biosensor for the detection of organophosphate pesticide residues in agricultural products. The research studied immobilized organophosphate hydrolase (OPH) mass and characterization of biosensor. The solution conductivity measurement in the conductivity cell consists of a 1 × 5 mm2 pair of electrodes screen printed carbon electrode (SPCE). The instrument is a converted local conductometer. From the results of study concluded that the optimum performance of the biosensor was obtained from the 105 μg OPH, at pH 8.5 with a response time of 45 seconds. In that condition the sensitivity of biosensor is 28.04 μS/ppm and 0.18 ppm detection limit and the maximum concentration of pesticide which can be measured is 1 ppm. Biosensors have been applied to measure pesticide residues in some vegetable samples.

Stretchable Strain Sensors Fabricated by Screen Printing of Silver Paste on the Surface Modified Transparent Elastomeric Polyurethane Films

Strain sensors for human-motion detection must offer high stretchability, high sensitivity, fast response, and high recovery speed. In this study, we choose silver paste as a sensing material and use a screen printing method to fabricate the strain sensor based upon an electrical-resistance mechanism. After curing elastomeric polyurethane film with a thickness of 150 μm on PET film, the polyester resin mixed with blocked isocyanate curing agent was coated as a masking layer to reduce the film’s stickiness. The effect of the polyester masking layer upon the silver paste screen printing process was examined using a rolling-ball-tack test, TGA analysis of polyester resins, and cured silver-electrode films. The cost-effective strain sensor fabricated by using silver paste and screen printing processes on the stretchable-polyurethane-substrate film showed high sensitivity and fast response in a strain range of up to 100%.

Size effect enabling additive-free MXene ink with ultrahigh conductivity for screen printing of wireless electronics

Facile preparation of additive-free inks with both high viscosity and high conductivity is critical for scalable screen printing of wireless electronics,yet very challenging.MXene materials exhibit excellent conductivity and hydrophilicity,showing great potential in the field of additive-free inks for screen printing.Here,we demonstrate the synthesis of additive-free two-dimensional(2D)titanium carbide MXene inks,and realize screen-printed MXene wireless electronics for the first time.The viscosity of MXene ink is solely regulated by tuning the size of MXene nanosheet without any additives,hence rendering the printed MXene film extremely high conductivity of 1.67×10^(5) S/m and fine printing resolution down to 0.05 mm on various flexible substrates.Moreover,radio frequency identification(RFID)tags fabricated using the additive-free MXene ink via screen printing exhibit stable antenna reading performance and superb flexibility.This article,thus offers a new route for the efficient,low-cost and pollution-free manufacture of printable electronics based on additive-free MXene inks.

Highly Concentrated,Conductive,Defect-free Graphene Ink for Screen-Printed Sensor Application

Conductive inks based on graphene materials have received significant attention for the fabrication of a wide range of printed and flexible devices.However,the application of graphene fillers is limited by their restricted mass production and the low concentration of their suspensions.In this study,a highly concentrated and conductive ink based on defect-free graphene was developed by a scalable fluid dynamics process.A high shear exfoliation and mixing process enabled the production of graphene at a high concentration of 47.5 mg mL^(−1)for graphene ink.The screen-printed graphene conductor exhibits a high electrical conductivity of 1.49×10^(4)S m^(−1)and maintains high conductivity under mechanical bending,compressing,and fatigue tests.Based on the as-prepared graphene ink,a printed electrochemical sodium ion(Na^(+))sensor that shows high potentiometric sensing performance was fabricated.Further,by integrating a wireless electronic module,a prototype Na^(+)-sensing watch is demonstrated for the real-time monitoring of the sodium ion concentration in human sweat during the indoor exercise of a volunteer.The scalable and efficient procedure for the preparation of graphene ink presented in this work is very promising for the low-cost,reproducible,and large-scale printing of flexible and wearable electronic devices.

Effect of processing parameters on in situ screen printing-assisted synthesis and electrical properties of Ti3SiC2-based structures

This work reports on the development of pastes containing Ti,TiC,Si,and C elementary powders for in situ synthesis of Ti3SiC2 via screen printing.Four paste compositions were manufactured using two powder mixtures(Ti/Si/C and Ti/TiC/Si/C)with different stoichiometry.The pastes were screen printed onto Al2O3 substrates and sintered at 1400℃in argon varying the dwell time from 1 to 5 h.The printed pastes containing TiC and excess of Si exhibited the lowest surface roughness and after 5 h sintering comprised of Ti3SiC2 as the majority phase.The electrical conductivity of this sample was found to range from 4.63×10^(4)to 2.57×10^(5)S·m^(-1)in a temperature range of 25-400℃.

Rheological properties and screen printability of UV curable conductive ink for flexible and washable E-textiles

As a critical component for the realization of flexible electronics,multifunctional electronic textiles(etextiles)still struggle to achieve controllable printing accuracy,excellent flexibility,decent washability and simple manufacturing.The printing process of conductive ink plays an important role in manufacturing e-textiles and meanwhile is also the main source of printing defects.In this work,we report the preparation of fully flexible and washable textile-based conductive circuits with screen-printing method based on novel-developed UV-curing conductive ink that contains low temperature and fast cure features.This work systematically investigated the correlation between ink formulation,rheological properties,screen printability on fabric substrates,and the electrical properties of the e-textile made thereafter.The rheological behaviors,including the thixotropic behavior and oscillatory stress sweep of the conductive inks was found depending heavily on the polymer to diluent ratio in the formulation.Subsequently,the rheological response of the inks during screen printing showed determining influence to their printability on textile,that the proper control of ink base viscosity,recovery time and storage/loss modulus is key to ensure the uniformity of printed conductive lines and therefore the electrical conductivity of fabricated e-textiles.A formulation with 24 wt%polymer and 10.8 wt%diluent meets all these stringent requirements.The conductive lines with 1.0 mm width showed exceptionally low resistivity of 2.06×10^(-5)Ωcm Moreover,the conductive lines presented excellent bending tolerance,and there was no significant change in the sample electrical resistance during 10 cycles of washing and drying processes.It is believed that these novel findings and the promising results of the prepared product will provide the basic guideline to the ink formulation design and applications for screen-printing electronics textiles.

Flexible carbon nanotube-enriched silver electrode films with high electrical conductivity and reliability prepared by facile screen printing

Flexible electrode films play critical and fundamental roles in the successful development of flexible electronic devices. In this study, carbon nanotubes（CNTs） were implanted into silver（Ag） ink to enhance the electrical conductivity and the reliability of the printed Ag electrode films. The fabricated carbon nanotubes-enriched silver（Ag-CNTs） electrode films were printed on the polyimide substrates by a facile screen printing method and sintered at a relatively low temperature. The resistivity of Ag-CNTs films was decreased by 62.27% compared with the pure Ag film. Additionally, the Ag-CNTs films exhibited excellent flexibility under a bending radius of 4 mm（strain ε = 2.09%） over 1000 cycles. Furthermore, the Ag-CNTs film displayed unchangeable electrical conductivity together with a strong adhesion after an accelerated aging test with 500 thermal shock cycles. These improvements were attributed to the AgCNTs interconnected network structure, which can provide electronic transmission channels and prevent cracks from initiating and propagating.

Screen printing of upconversion NaYF4:Yb3+/Eu3+ with Li+ doped for anti-counterfeiting application

Li ions affect the upconversion efficiency by changing the local crystal field of the luminescent center. Herein, in order to improve the upconversion efficiency of NaYF4:Yb3+/Eu3+, a series of NaYF4:Yb3+/Eu3+micro-particles with different Li+doping concentrations were synthesized by the hydrothermal synthesis method, respectively.Firstly, the structure and morphology of NaYF4:Yb3+/Eu3+upconversion micro-particles(UCMPs) with different doping concentrations were analyzed by X-ray diffraction and a scanning electron microscope(SEM). SEM results show that the UCMPs are not only highly crystallized, but also have hexagons with different Li+concentrations of NaYF4:Yb3+/Eu3+. X-ray diffraction shows that the crystal field around Eu3+changes with the increase of Li+concentration. Then, the fluorescence spectrum of NaYF4:Yb3+/Eu3+was studied under the irradiation of a 980 nm laser. The results show that the fluorescence intensity of NaYF4:Yb3+/Eu3+with2% Li+is the strongest, which is twice the intensity of NaYF4:Yb3+/Eu3+without Li+. Finally, the fluorescence imaging analysis of NaYF4:Yb3+/Eu3+with 2% Li+concentration was carried out. The UCMPs are used to screen printing to evaluate the imaging effect on different sample surfaces. The results show NaYF4:Yb3+/Eu3+(with 2% Li+) has great application prospects in anti-counterfeiting recognition.

Microfibrillated Cellulose Based Ink for Eco-Sustainable Screen Printed Flexible Electrodes in Lithium Ion Batteries

Free organic solvent ink containing graphite, carboxymethyl cellulose and microfibrillated cellulose as active material, dispersing and binder, respectively, has been formulated to produce flexible and eco- sustainable electrodes for lithium ion batteries. Content ratio of components and dispersion protocol were tailored in order to have theological properties suitable for a large and cheap manufacturing process as well as screen printing. The bio-sourced printed electrodes exhibit a high porosity value of 70% that limits the electrochemical performances. However, the calendering process enhances electrode performances by increasing the reversible capacity from 85 until 315 mAh/g and reducing porosity to an optimal value of 34%. Moreover the introduction of 2% w/w of monofluoro-ethylene carbonate in the electrolyte reduced their reversible capacity loss of 11% in the printed electrode.

Screen printing process control for coating high throughput titanium dioxide films toward printable mesoscopic perovskite solar cells

Screen printing technique has been widely applied for the manufacturing of both traditional silicon solar cells and emerging photovoltaics such as dyesensitized solar cells(DSSCs)and perovskite solar cells(PSCs).Particularly,we have developed a printable mesoscopic PSC based on a triple layer scaffold of TiO2/ZrO2/carbon.The deposition of the scaftold is entirely based on screen printing process,which provides a promising prospect for low-cost photovoltaics.However,the optimal thickness of the TiO2 layer for fabricating efficient printable PSCs is much smaller than the typical thickness of screen printed films.Here,we tune the concentration of the pastes and the printing parameters for coating TiO?films,and successfully print TiO2 films with the thickness of 500-550 nm.The correlation between the thickness of the films and printing parameters such as the solid content and viscosity of the pastes,the printing speed and pressure,and the temperature has been investigated.Besides,the edge effect that the edge of the TiO2 films possesses a much larger thickness and printing positional accuracy have been studied.This work will significantly benefit the further development of printable mesoscopic PSCs.

Application of graphite screen printed electrode modified with dysprosium tungstate nanoparticles in voltammetric determination of epinephrine in the presence of acetylcholine

The current work focuses on the development of a sensitive and selective electrochemical device based on a graphite screen printed electrode modified with Dy2（WO4）3 nanoparticles（DWO/SPE） for the analysis of epinephrine in samples also containing acetylcholine. The study proves that the sensor has excellent electron-mediating behavior in the oxidation of epinephrine in a 0.1 mol/L phosphate buffer solution（PBS）（pH 7.0）. The application of the DWO/SPE in differential pulse voltammetry（DPV） is found to lead to distinct response for the oxidation of epinephrine and acetylcholine, with the potentials of the epinephrine and acetylcholine peaks（△Ep） to be 550 mV apart. The detection limits of the method for epinephrine and acetylcholine are 0.5 and 0.7 μmol/L（S/N = 3） and the responses are found to be linear in the concentration ranges of 1.0-900.0 μmol/L and 1.0-1200.0 μmol/L in a PBS buffer（pH = 7.0）respectively. The modified electrode was used for the detection of epinephrine and acetylcholine in real samples and found to produce satisfactory results. These results can be a proof that Dy2（WO4）3 nanoparticles can find promising applications in electrochemical sensors to be used for the analysis of（bio）chemical species.

SYNTHESIS OF CoFe_(2)O_(4)/Pb(Zr_(0.53)Ti_(0.47))O_(3)MULTIFERROIC COMPOSITE THICK FILMS BY LOW-SINTERING-TEMPERATURE SCREEN PRINTING METHOD

CoFe_(2)O_(4)/Pb(Zr_(0.53)Ti_(0.47))TO_(3)(abbreviated as CFO/PZT)multiferroic composite thick films were successfully fabricated on alumina substrate with gold bottom electrode by screen printing method at a low-sintering temperature.The processing included the modi fication and dispersion of ferromagnetic CFO powder and ferroelectric PZT powder,the preparation of uniform pastes,and the selection of proper annealing temperature for composite thick films.Transmission electron microscopic pictures(TEM)indicated the submicron meter of particles size for both CFO and PZT particles.After annealing at 900℃ for 1 h in air,tape test con firmed the quality of multiferroic thick films as well as pure CFO and PZT films.X-ray diffraction(XRD)showed a coexistence of CFO and PZT phases;furthermore,a smooth surface was observed through scanning electron microscopic(SEM)pictures along with the sharp cross-sectional picture,indicative of 100
m of film thickness.Ferromagnetic and ferroelectric properties were observed in CFO/PZT films simultaneously at room temperature.Compared with the reported CFO/PZT multiferrroic thin films,the present ferromagnetic property was closing to that of the chemical solgel synthesized film and even that from the physical pulsed laser deposition technique.However,the ferroelectric property showed a degenerated behavior,possible reasons for this was discussed and further optimization was also proposed for the potential multifunctional application.

Noninvasive Label-Free Detection of Cortisol and Lactate Using Graphene Embedded Screen-Printed Electrode

A sensitive and specific immunosensor for the detection of the hormones cortisol and lactate in human or animal biological fluids, such as sweat and saliva, was devised using the label-free electrochemical chronoamperometric technique. By using these fluids instead of blood,the biosensor becomes noninvasive and is less stressful to the end user, who may be a small child or a farm animal.Electroreduced graphene oxide(e-RGO) was used as a synergistic platform for signal amplification and template for bioconjugation for the sensing mechanism on a screenprinted electrode. The cortisol and lactate antibodies were bioconjugated to the e-RGO using covalent carbodiimide chemistry. Label-free electrochemical chronoamperometric detection was used to analyze the response to the desired biomolecules over the wide detection range. A detection limit of 0.1 ng mL^(-1) for cortisol and 0.1 mM for lactate was established and a correlation between concentration and current was observed. A portable, handheld potentiostat assembled with Bluetooth communication and battery operation enables the developed system for point-of-care applications. A sandwich-like structure containing the sensing mechanisms as a prototype was designed to secure the biosensor to skin and use capillary action to draw sweat or other fluids toward the sensing mechanism. Overall, the immunosensor shows remarkable specificity, sensitivity as well as the noninvasive and point-of-care capabilities and allows the biosensor to be used as a versatile sensing platform in both developed and developing countries.

Bending and Washing Reliabilities of Screen-Printed UHF RFID Tags Based on Woven Water-Mark Fabric

Compared with bar code and quick response( QR) code in the storage and retailing management of textiles, the ultra-high frequency( UHF) radio frequency identification( RFID) tags have high information capacity as well as reliability in complex environmental conditions. In this study,the UHF RFID tags with perfect integration with textiles are assembled with screen-printed antenna on woven water-mark nylon fabric and Alien UHF integrated circuit( IC), and their reading performance under various washing and bending conditions is evaluated by an RFID reader. The results show that the tags after fifty bending( both arch and sink) cycles of screen-printed antenna still have reading distance more than 5.5 m,and an average reading distance is over 4.0 m after five washing cycles. The experimental results demonstrate that the tag antenna on the water-mark fabric can be manufactured by the screen-printing technology,and a coating process on this fabric facilitates the reading performance and the resistance against complex mechanical impact.

Voltammetric determination of venlafaxine as an antidepressant drug employing Gd_2O_3 nanoparticles graphite screen printed electrode

Graphite screen printed electrode modified with Gd_2 O_3 nanoparticles(Gd_2 O_3/SPE) was developed for the determination of venlafaxine(VF). The Gd_2 O_3 nanoparticles were thoroughly characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and X-ray diffraction(XRD) analyses. To study the electrochemical behaviour of venlafaxine cyclic voltammetry(CV), chronoamperometry(CHA)and differential pulse voltammetry(DPV) were employed. These studies reveal that the oxidation of venlafaxine is facilitated at Gd_2 O_3/SPE. After optimization of analytical conditions, analysis of venlafaxine using the modified electrode in 0.1 mol/L PBS(pH 7.0) demonstrates that the peak currents corresponding to venlafaxine vary linearly with its concentration in the range of 5.0 ×10^(-6)-9.0 × 10^(-4) mol/L. The detection limit(S/N = 3) of 2.1 × 10^(-7) mol/L is obtained for venlafaxine using DPV. The prepared modified electrode benefits from advantages such as simple preparation method, high sensitivity and low detection limit.Moreover, the evaluation of practical applicability of this proposed method is successful in the identification of venlafaxine in pharmaceutical formulations, urine and water samples.

Anodic voltammetric determination of gemifloxacin using screen-printed carbon electrode

The electrochemical oxidation behavior and voltammetric assay of gemifloxacin were investigated using differential-pulse and cyclic voltammetry on a screen-printed carbon electrode.The effects of pH,scan rates,and concentration of the drug on the anodic peak current were studied.Voltammograms of gemifloxacin in Tris-HCl buffer（pH 7.0） exhibited a well-defined single oxidation peak.A differential-pulse voltammetric procedure for the quantitation of gemifloxacin has been developed and suitably validated with respect to linearity,limits of detection and quantification,accuracy,precision,specificity,and robustness.The calibration was linear from 0.5 to 10.0 μM,and the limits of detection and quantification were 0.15 and 5.0 μM.Recoveries ranging from 96.26% to 103.64% were obtained.The method was successfully applied to the determination of gemifloxacin in pharmaceutical tablets without any pre-treatment.Excipients present in the tablets did not interfere in the assay.

Surface tension and screen printing precision

With continued demands for better performance of VLSI,the electronic industry haspaid much attention to packaging technology.Thick-film technology is important in pack-age.The increases of circuit densities in high-density microelectronic packaging requestreduction of the width of printing lines.