Ink-jet Technique Research Articles

Reconfigurable Liquid Whispering Gallery Mode Microlasers.

Engineering photonic devices from liquid has been emerging as a fascinating research avenue. Reconfigurably tuning liquid optical micro-devices are highly desirable but remain extremely challenging because of the fluidic nature. In this article we demonstrate an all-liquid tunable whispering gallery mode microlaser floating on a liquid surface fabricated by using inkjet print technique. We show that the cavity resonance of such liquid lasers could be reconfigurably manipulated by surface tension alteration originated from the tiny concentration change of the surfactant in the supporting liquid. As such, remarkable sensing of water-soluble organic compounds with a sensitivity of free spectral range as high as 19.85 THz / (mol · mL−1) and the detectivity limit around 5.56 × 10−3 mol · mL−1 is achieved. Our work provides not only a novel approach to effectively tuning a laser resonator but also new insight into potential applications in biological, chemical and environmental sensing.

Organic Sensor for Cardiomyocytes Research

Organic electronic devices offer a convenient solution for bioelectronic sensor applications due to the biocompatibility of organic semiconductors and biologic tissues. So-called biosensors can convert electrochemical processes connected to cell membranes into electronic signals. A matrix of such biosensors can simultaneously scan a number of biological samples as well as living tissue in the body. The core of the device is a transistor, today mostly OECT (Organic Electro Chemical Transistor) fabricated by thin film or printing technique from semiconducting biocompatible polymer PEDOT:PSS (poly(3, 4-ethylenedioxythiophene) polystyrene sulfonate). Such transistors were printed both by inkjet and screen-printing technique and their main characteristics are presented.

Design and optimization of a high temperature microheater for inkjet deposition

Inkjet deposition has become a promising additive manufacturing technique due to its fast printing speed, scalability, wide choice of materials, and compatibility for multi-material printing. Among many different inkjet techniques, thermal inkjet, led by Hewlett-Packard and Canon, is the most successful inkjet technique that uses a microheater to produce a pressure pulse for ejecting droplets by vaporizing the ink materials in a timespan of microseconds. Thermal inkjet has been widely adopted in many commercial 3D inkjet printers (e.g., 3D Systems ProJet X60 series) due to its low cost, high resolution, and easy operation. However, the viscosity of the printable materials has been limited to less than 40 cP due to insufficient energy provided inside the nozzle to overcome the viscous dissipation of energy. This paper presents a study on the design and optimization of a high temperature microheater with a target heating temperature of more than 600 °C (compared to ~300 °C for current printhead) to increase the energy supply to the nozzle. The benefits are fourfold: (1) higher temperature will lead to faster vaporization of ink and thus higher jetting frequency and print speed, (2) higher temperature will make it possible for jetting materials with higher boiling points, (3) higher temperature will reduce the viscosity of the ink and thus the viscous dissipation of energy, and (4) higher energy supply will increase the magnitude of the pressure pulse for printing more viscous materials. In this paper, a high-temperature microheater was designed with the following objectives: to reduce thermal stress in heaters and to minimize uneven heat distribution. A literature survey was first conducted on design, fabrication, and operation of thin-film resistive microheaters. A multiphysics numerical model was then developed to simulate electrical, thermal, and mechanical responses of the microheater. The model was validated by comparison to experimental data and existing models obtained from literature. With proper parameterization of the design geometry, the geometry of the microheater is optimized using a particle swarm optimization method. Results show the optimized high-temperature microheater successfully operates at temperatures in excess of 600 °C. The design optimization enabled better characteristics for even heat distribution and minimizing stress. The design approach can serve as a fundamental means of design optimization for microheaters.

Multicolor lasing prints

This work demonstrates mass production of printable multi-color lasing microarrays based on uniform hemispherical microcavities on a distributed Bragg reflector using inkjet technique. By embedding two different organic dyes into these prints, optically pumped whispering gallery mode microlasers with lasing wavelengths in green and red spectral ranges are realized. The spectral linewidth of the lasing modes is found as narrow as 0.11 nm. Interestingly, dual-color lasing emission in the ranges of 515–535 nm and 585–605 nm is simultaneously achieved by using two different dyes with certain ratios. Spectroscopic measurements elucidate the energy transfer process from the green dye (donor) to the red one (acceptor) with an energy transfer efficiency up to 80% in which the nonradiative Förster resonance energy transfer dominates. As such, the acceptor lasing in the presence of donor exhibits a significantly lower (∼2.5-fold) threshold compared with that of the pure acceptor lasing with the same concentration.

Photocatalytic and Antimicrobial Activity of Printed Hybrid Titania/Silica Layers.

Stable mixed dispersion of TiO2 and SiO2 was developed and hybrid TiO2/SiO2 layers were fabricated by the direct inkjet patterning technique. The prepared layers were tested for photoinduced hydrophilicity and their photocatalytic activity was tested using stearic acid and dichloroindophenol as model compounds. The antimicrobial activity of prepared layers was tested and evaluated by the traditional plate counting method according to ISO 27447:2009, using Escherichia coli CCM 3988. Material printing proved to be well suited for the deposition of this complex nanoparticulate ink and samples with variable thickness were conveniently fabricated. Printed layers are able to change their surface properties from hydrophobic to superhydrophilic and also decompose the model contaminants rapidly.

Evaluating silver tracks conductivity on flexible surfaces

The development of electric circuit fabrication on flexible polymer substrates has attracted significant interest as a pathway to low-cost, comfortable movement and large-area electronics among direct printing techniques. The term electronic textiles, or e-textiles, are used to denote the class of fabric structures that integrate electronic elements with textiles and can sense changes in its environment and respond to it. This new class of wearable electronic systems is being designed to meet new and innovative applications in the military, public safety, healthcare, space exploration, sports and consumer fitness fields. In this paper the inkjet printing technique (office thermal inkjet printer) was used as a simple method to chemically deposit silver Nanoparticles (85–300 nm) to the flexible surface. It is done by ejection of silver nitrate and ascorbic acid as a reducing agent to attain nanometals on the surface. Ink concentration and repeating the printing sequence of each ink determines molar ratio ejection of ink and is found to be necessary to be evaluated in order to attain the highest level of conductivity. The main purpose of this work is to gain the highest conductive printed tracks by using statistical design of experiment method on the fabric surface by applying inkjet technique. By optimizing the mentioned parameters, the highest conductivity of printed flexible tracks on the surface of paper is gained 8.0635 × 105 S/m and the result for polyester fabric is obtained 1.2417 × 104 S/m whereas metallic silver wire has a conductivity of 6.173 × 107 S/m.

Extreme ultra-low lasing threshold of full-polymeric fundamental microdisk printed with room-temperature atmospheric ink-jet technique

We experimentally demonstrated an extreme ultra-low lasing threshold from full-polymeric fundamental microdisk cavities fabricated by a novel fabrication method, the ink-jet printing method, which is much simpler and easier than previous methods such as lithography. The ink-jet printing method provides additive, room-temperature atmospheric, rapid fabrication with only two steps: (i) stacking cladding pedestal and waveguiding disk spots using the ink-jet technique, and (ii) partial etching of the cladding pedestal envelope. Two kinds of low-viscosity polymers successfully formed microdisks with high surface homogeneity, and one of the polymers doped with LDS798 dye yielded whispering-gallery-mode lasing. The fundamental disks exhibited an extremely ultra-low lasing threshold of 0.33 μJ/mm2 at a wavelength of 817.3 nm. To the best of our knowledge, this lasing threshold is the lowest threshold obtained among both organic and inorganic fundamental microdisk cavity lasers with a highly confined structure.

A comparative analysis of printing techniques by using an active concentric ring electrode for bioelectrical recording

Purpose – This paper aims to present a comparison between three types of manufacturing techniques, namely, screen-printed, inkjet and gravure, using different types of inks, for the implementation of concentric ring electrodes which permit estimation of Laplacian potential on the body surface. Design/methodology/approach – Flexible concentric ring electrodes not only present lower skin–electrode contact impedance and lower baseline wander than rigid electrodes but are also less sensitive to interference and motion artefacts. The above three techniques allow printing of conductive inks on flexible substrates, and with this work, the authors aim to study which is the best technique and ink to obtain the best electrode response. Findings – From the results obtained regarding ink thickness, resistivity, electrode resistance and other performance parameters derived from electrocardiographic signal recording tests, it can be said that concentric electrodes using the screen-printing and inkjet techniques are suitable for non-invasive bioelectric signal acquisition. Originality/value – The development of new types of inks and substrates for the electronics industry and the adaptation of new manufacturing techniques allow for an improvement in the development of electrodes and sensors.

Local deposition using an electrostatic inkjet technique with a nanopipette for photomask repair

We have developed local deposition techniques using a nanopipette for photomask repair. The nanopipette is a tapered glass capillary with an aperture size of sub-micrometer in diameter. The nanopipette was filled with a nanoink containing Au nano-particles with a diameter of around 3 nm. As a driving force of the ink deposition, electrostatic ink-jet method was employed. By applying a pulse voltage on an electrode inserted into the nanopipette, a Taylor cone is formed and discharged at the edge of the pipette. As a result, the droplet is deposited on the substrate. By controlling parameters of the pipette-surface distance, pulse width and applied voltage, it is possible to control the amount of deposition. The smallest size of dot with sub-micrometer in diameter is achieved with the optimised parameters. The simple deposition processing using the nanopipette can be a strong candidate of photomask repairing method for repairing size of micro to sub-micrometer scale.

Comparison of barium titanate thin films prepared by inkjet printing and spin coating

In this paper, barium titanate films were prepared by different deposition techniques (spin coating, office Epson inkjet printer and commercial Dimatix inkjet printer). As inkjet technique requires special rheological properties of inks the first part of the study deals with the preparation of inks, whereas the second part examines and compares structural characteristics of the deposited films. Inks were synthesized by sol-gel method and parameters such as viscosity, particle size and surface tension were measured. Deposited films were examined by optical and scanning electron microscopy, XRD analysis and Raman spectroscopy. The findings consider advantages and disadvantages of the particular deposition techniques.

Experimental studies on formation, spreading and drying of inkjet drop of colloidal suspensions

Abstract In this study the dynamic characteristics of inkjet drops from generation to drying are investigated experimentally. The inkjet drops were made from suspensions of 2 μm polystyrene spheres dispersed in octanol or heptanol. The particle loading was 5–25 vol%. Bare glass surfaces and aldehyde coated surfaces were used as solid substrates. The result shows that the presence of particles in the liquid is insensitive to the drop generation characteristics and the particles are uniformly distributed within the drop. At the impact stage, the spreading characteristics are practically the same regardless of Weber number considered here and presence particles. At the capillary spreading stage, the drop of suspension in octanol shows the same behavior as the drop of pure octanol. The drying characteristics are quite different depending on the presence of particles and/or the wetting characteristics of the solid substrate. Especially, the drying stage is closely related with the spreading stage in the case of suspensions. On the small contact angle surface, particles are arranged parallel to the contact line during the capillary spreading stage. They become fully arranged in the crystalline form over the whole surface at the last stage of drying by the attractive surface tension force between partially immersed particles. On the large contact angle surface, particles move toward the rim by the outward flow. It is demonstrated that a crystalline monolayer of particles can be obtained by the inkjet technique.

Automation Highlights from the Literature

Automation Highlights from the Literature

Three-Dimensional Macroporous Graphene Foam Filled with Mesoporous Polyaniline Network for High Areal Capacitance

Bicontinuous macroporous graphene foam composed of few-layered graphene sheets provides a highly conductive platform on which to deposit mesoporous polyaniline via incorporation of electrodeposition and inkjet techniques. The experimental results exhibit that the coating polyaniline thin layer on the surface of three-dimensional graphene foam via electrodeposition is of importance for changing the hydrophobic surface to a hydrophilic one and for the subsequent filling of the mesoporous polyaniline network into the macroporous graphene foam. The porous polyaniline network with high pseudocapacitance is highly efficient for adjusting the pore structure and capacitive properties of graphene foam. When used as electrode materials for supercapacitors, the resulted graphene foam–polyaniline network with high porosity renders a large areal capacitance of over 1700 mF cm–2, which is over two times the enhancement in comparison with the pure graphene foam and polyaniline thin layer coated one. The ultrahigh areal capacitance benefits from the synergistic effect of the good conductive graphene backbone and high pseudocapacitive polyaniline.

Inkjet monitoring technique with quartz crystal microbalance (QCM) sensor for highly reproducible antibody immobilization

We demonstrate that a calibrated amount of a biomolecule can be microdeposited using a commercially available quartz crystal microbalance (QCM) and a piezoelectric inkjet head with a flattened surface surrounding the ejection hole. Covering the QCM with a stainless-steel cover perforated with a precisely-machined hole both significantly decreased background noise due to external sources such as air flow and temperature fluctuations and allowed accurate droplet ejection at a constant temperature. Anti-c reactive protein antibody solution (anti-CRP; 1.0mg/ml) was continuously ejected onto a microchannel target using a piezoelectric injector; its microdeposition was monitored shot-by-shot using a 30MHz QCM. The dispersion of the QCM frequency change per shot decreased from 7.87 to 1.01Hz when a perforated stainless-steel cover was installed. The primary antibody was precisely deposited on the target with high reproducibility. The variation in luminescence measured by enzyme-linked immunosorbant assay (ELISA) decreased from 9.67% to 1.16% when calibrating the amount of primary antibody deposition with this developed technique.

All-Printed Paper Memory

We report the memory device on paper by means of an all-printing approach. Using a sequence of inkjet and screen-printing techniques, a simple metal–insulator–metal device structure is fabricated on paper as a resistive random access memory with a potential to reach gigabyte capacities on an A4 paper. The printed-paper-based memory devices (PPMDs) exhibit reproducible switching endurance, reliable retention, tunable memory window, and the capability to operate under extreme bending conditions. In addition, the PBMD can be labeled on electronics or living objects for multifunctional, wearable, on-skin, and biocompatible applications. The disposability and the high-security data storage of the paper-based memory are also demonstrated to show the ease of data handling, which are not achievable for regular silicon-based electronic devices. We envision that the PPMDs manufactured by this cost-effective and time-efficient all-printing approach would be a key electronic component to fully activate a paper-based circuit and can be directly implemented in medical biosensors, multifunctional devices, and self-powered systems.

An inkjet vision measurement technique for high-frequency jetting.

Inkjet technology has been used as manufacturing a tool for printed electronics. To increase the productivity, the jetting frequency needs to be increased. When using high-frequency jetting, the printed pattern quality could be non-uniform since the jetting performance characteristics including the jetting speed and droplet volume could vary significantly with increases in jet frequency. Therefore, high-frequency jetting behavior must be evaluated properly for improvement. However, it is difficult to measure high-frequency jetting behavior using previous vision analysis methods, because subsequent droplets are close or even merged. In this paper, we present vision measurement techniques to evaluate the drop formation of high-frequency jetting. The proposed method is based on tracking target droplets such that subsequent droplets can be excluded in the image analysis by focusing on the target droplet. Finally, a frequency sweeping method for jetting speed and droplet volume is presented to understand the overall jetting frequency effects on jetting performance.

Interfacial sol–gel processing for preparation of porous titania particles using a piezoelectric inkjet nozzle

The aim of the present work is to apply the liquid–liquid interfacial crystallization using a piezoelectric inkjet nozzle to the sol–gel processing. The instillation process was compared with the batch process to elucidate the effectiveness of the inkjet technique on the liquid–liquid interfacial sol–gel processing. The effect of frequency and water concentration in titanium tetraisopoxide (TTIP) solution on titania particle properties was investigated for sol–gel processing with a piezoelectric inkjet nozzle. Titania particles produced by each process were calcined at 500°C. The crystal structure, morphology, pore size distribution and specific surface area of titania particles were evaluated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen physisorption measurement. The photocatalytic activity of titania particles was evaluated by the photodegradation of methylene blue solution under UVC light irradiation.Monodispersed titania particles could be produced by instillation sol–gel processing of hexane using a piezoelectric inkjet nozzle. Titania particles prepared at 1500Hz were spherical while titania particles prepared at 1000Hz and 3000Hz were non-spherical. The number of particulate fracture increased with water concentration in TTIP solution. The inkjet nozzle-mediated instillation processing was found to be a promising way to create porous titania particles with a high photocatalytic activity.

Direct writing of bio-functional coatings for cardiovascular applications

The surface modification of metallic biomaterials is of critical importance to enhance the biocompatibility of surgical implant materials and devices. This article investigates the use of a direct-write inkjet technique for multilayer coatings of a biodegradable polymer (polyester urethane urea (PEUU)) embedded with an anti-proliferation drug paclitaxel (Taxol). The direct-write inkjet technique provides selective patterning capability for depositing multimaterial coatings on three-dimensional implant devices such as pins, screws, and stents for orthopedic and vascular applications. Drug release profiles were studied to observe the influence of drug loading and coating thickness for obtaining tunable release kinetics. Platelet deposition studies were conducted following ovine blood contact and significant reduction in platelet deposition was observed on the Taxol loaded PEUU substrate compared with the unloaded control. Rat smooth muscle cells were used for cell proliferation studies. Significant reduction in cell growth was observed following the release of anti-proliferative drug from the biopolymer thin film. This research provides a basis for developing anti-proliferative biocompatible coatings for different biomedical device applications.

Morphology control of amino acid particles in interfacial crystallization using inkjet nozzle

The aim of this study is to apply the inkjet technique to liquid–liquid interfacial crystallization. Instillation with an inkjet nozzle was compared with the batch process in order to evaluate the effectiveness of the inkjet technique for controlling particle morphology. The effects of amino acid solution concentration and organic solvent type on particle properties were investigated for instillation with an inkjet nozzle. The morphology of alanine and glycine particles was observed by scanning electron microscopy and X-ray powder diffraction. The inner structure of alanine and glycine particles was investigated by cutting particles with an ion milling machine. Controlling particle size by adjusting the droplet size in the instillation with an inkjet nozzle was found to be feasible. Most alanine and glycine particles produced by instillation were spherical, whereas most particles produced by the batch process were non-spherical. A higher concentration of amino acid in the solution may lead to the generation of solute particles at the spherical interface. It was found that the surface structure of alanine particles changed when using two kinds of organic solvents as anti-solvents. In addition, instillation allowed for β-glycine to be identified and the crystal polymorph of the particles to be controlled.

Assembly of a Versatile Micro Dispenser Using Off-The-Shelf Components for Applications in Microfluidics

AbstractWe designed and constructed a drop-on-demand (DOD) droplet dispenser using the piezo inkjet technique that is simple to construct and operate and makes use of readily available components. The droplet dispenser can be easily fitted with cost effective glass nozzles and can be readily tuned to produce consistent drop sizes. The dynamics of the droplet motion are obtained using a calibrated analog video imaging system. We observed very high accelerations for the ejected droplets that corroborate with the applied drive pulse amplitudes. The acceleration measured, near the ejection nozzle, was many times the acceleration of gravity with the largest value of 34g’s. We successfully dispensed glycol water solutions and aqueous suspensions of titanium oxide nanoparticles, with values greater than 10 in the measured pH. For the inkjet droplets deposited on smooth gold/chromium substrates (±3nm surface roughness variation), we observed the well-known coffee ring effect using optical microscopy and nanoparticle morphology using an atomic force microscope.