Dispenser Printing Research Articles

Piezoelectric dispenser printing and intense pulsed light sintering of AgNW/PEDOT:PSS hybrid transparent conductive films

A hybrid transparent conductive films (TCFs) combining silver nanowires (AgNWs) and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) was fabricated using a piezoelectric dispenser printing method. The innovation lies in optimizing the ink composition and employing intense pulsed light sintering to enhance the TCF's performance. The optimized AgNW/PEDOT:PSS mixture, with an 8:2 ratio, achieved a figure of merit (FOM) of 28.05 × 10-3Ω-1, corresponding to a sheet resistance of 9.93 Ω sq-1and a transmittance of 88.0%. This represents a significant improvement over the pre-sintering FOM of 24.09 × 10-3Ω-1. Additionally, the hybrid TCFs exhibited outstanding structural stability, maintaining functionality after 7000 mechanical bending cycles. The results enable applications in flexible optoelectronic devices, and highlight the potential of this method to produce high-performance, flexible, and durable transparent electrodes, advancing the development of next-generation optoelectronic devices.

On 3D Dispenser Printing of MnO2 Reinforced PVDF Matrix for Recycling of Dry Cell

On 3D Dispenser Printing of MnO2 Reinforced PVDF Matrix for Recycling of Dry Cell

On the Tertiary Recycling of PVDF Composite Matrix by 3D Dispenser Printing

On the Tertiary Recycling of PVDF Composite Matrix by 3D Dispenser Printing

Flexible low profile UWB antenna on polyimide film based on silver nanoparticle direct-write dispenser printing for wireless applications

Flexible low profile UWB antenna on polyimide film based on silver nanoparticle direct-write dispenser printing for wireless applications

Low Dielectric Constant and Anisotropic Mechanical Properties of Dispenser‐Printed Polyetherimide Films Using Two‐Step Thermal Treatment

Back Cover: In article 2200213 by Jae-Do Nam and co-workers, polyetherimide-based ink is printed using dispenser printing, which is facile and has an advantage in shape flexibility. The randomly distributed polymer chains can be aligned following the printing directions resulting in characteristic anisotropic mechanical properties.

High-Throughput Manufacturing of Flexible Thermoelectric Generators for Low- to Medium-Temperature Applications Based on Nano-Silver Bonding

The melting point of the commercial soldering materials is a limiting factor for the functionality of the thermoelectric generators (TEGs) in medium-temperature ranges higher than 200 °C. Hence, using a proper bonding method which could be formed at lower temperatures and withstand higher temperatures is inevitable to unlock the full potential of the commercial thermoelectric materials. Nano-silver bonding is known as the “low-temperature joining technique” due to its lower processing temperature compared with the other conventional bonding approaches. This study is focused on presenting a fabrication process of flexible TEGs using nano-silver (Ag) paste bonding. The pellets of thermoelectric materials were prepared by wire cutting of bismuth telluride ingots in desired sizes. The electrical interconnects between the thermoelectric legs are nano-silver paste traces printed by a digitally control dispenser printer. Reliability of the thermoelectric module was evaluated from room temperature up to 300 °C as well as conducting the cyclic bending test. The proposed fabrication technique is similar to the flexible hybrid electronics (FHE) concept, which is scalable for high-throughput manufacturing, such as roll-to-roll or sheet-to-sheet printing.

Dispenser Printed Bismuth‐Based Magnetic Field Sensors with Non‐Saturating Large Magnetoresistance for Touchless Interactive Surfaces (Adv. Mater. Technol. 10/2022)

Printed Magnetic Field Sensors In article number 2200227, Mykola Vinnichenk, Denys Makarov, and co-workers present dispenser printing of magnetic field sensors based on bismuth powder. Benefiting from the non-saturating large magnetoresistance effect, this technology enables scalable large-area printing of sensors with broad detection range on flexible and rigid substrates. Touchless interactive surfaces based on dispenser-printed magnetically sensitive devices are demonstrated.

Low Dielectric Constant and Anisotropic Mechanical Properties of Dispenser‐Printed Polyetherimide Films Using Two‐Step Thermal Treatment

AbstractAlthough polyetherimide (PEI) has attracted attention owing to its good dielectric properties, superior mechanical properties, and thermal/chemical stabilities, there is still a lack of methodology to fabricate PEI films in desired shapes directly on devices. In this study, a dispenser printing method to fabricate sophisticated 2D PEI structures is introduced. As dispenser printing is a solution‐based process, PEI ink is prepared by dissolving PEI in N‐methyl pyrrolidone (NMP). The printing conditions are controlled by optimizing the pneumatic pressure and viscosity of the inks with various ratios of PEI and NMP, followed by a two‐step heat treatment to develop fine PEI films. The dielectric constant of the PEI film increases from 2.28 to 2.61 with the corresponding secondary heating time of 1–5 h, which is much lower than the theoretical value owing to the free volume and loosely entangled polymer chains generated from the shear forces in printing and solvent evaporation. Furthermore, the film exhibits anisotropic mechanical properties in different printing directions, stemming from the alignment effect of the polymer molecules. It is believed that the developed PEI films and the facile methodology can be diversely tuned to provide new insights into material utilization, further extending the application fields.

Dispenser Printing with Electrically Conductive Microparticles

Electrically conductive textiles for wearable smart devices are in increasing demand [1]. The advantages of flexible fabric structures are combined with electronic functions, such as sensing or actuating, energy harvesting or illuminating, for the design of a multitude of smart textiles. Those functions are often created by applying conductive layers or patterns onto the textile surface with two-phase systems based on conductive filler particles in polymeric binders. However, those systems alter the textile-typical properties regarding haptic, drape, flexibility or weight, depending on the type of conductive particle used, i.e., metal-or carbon-based ones. Generally, electrical conductivity increases with the increase of conductive filler concentration. The relation between the various factors determining the electrical behavior as well as the percolation threshold for some dispersions and in particular the size and shape of the filler particles were previously assessed for planar coatings [2]. In this research work electrically, conductive patterns were printed with dispenser printing technology using such two-phase dispersions based on polyurethane and polyacrylate binders and various metal microparticle flakes. With this application method linear resistance of approx. 25 to 100 Ohm per 100 cm depending on the textile structure could be realized, which was not even significantly reduced by household washing at 40°C or abrasion by Martindale.

Flexible thermoelectric generators prepared by dispenser printing technology

Flexible thermoelectric generators (f-TEGs) can be used to supply power to wearable electronics or remote wireless sensors. Dispenser printing is an attractive f-TEG fabrication technique due to its direct-writing capability and cost-saving advantage. In this paper, we report the investigations of printing paste rheology, thermoelement sintering process and output performance of dispenser-printed f-TEGs. The sintered p- and n-type thermoelements exhibit high thermoelectric power factors of 23.2 and 19.1 μW/cm·K2, respectively, after optimization of both paste ingredients and sintering temperature. A planar f-TEGs containing 8 pairs of thermoelements can deliver a power of 68 μW under a temperature difference of 33 K. No performance degradation is detected for the f-TEG after 500 cycles of bending on a stainless-steel rod of 20 mm radius. The feasibility of powering a light-emitting-diode and charging a battery with a modular TEG containing seven f-TEGs is demonstrated.

Dispenser Printed Bismuth‐Based Magnetic Field Sensors with Non‐Saturating Large Magnetoresistance for Touchless Interactive Surfaces

AbstractPrinted magnetic field sensors enable a new generation of human‐machine interfaces and contactless switches for resource‐efficient printed interactive electronics. As printed magnetoresistors rely on scarce or hard to manufacture magnetosensitive powders, their scalability and demonstration of printing with industry‐grade technologies are the key material science challenges. Here, the authors report dispenser printing of a commodity scale nonmagnetic bismuth‐based paste processed by large area laser sintering to obtain printed magnetoresistive sensors. The sensors are printed on different substrates including ceramics, paper, and polymer foils. It is validated experimentally that the peculiar quantum large orbital magnetoresistive effect remains effective in printed bismuth sensors, allowing their operation in high magnetic fields. The sensors reveal up to 146% resistance change at 5 T at room temperature with a maximum resolution of 2.8 μT. If printed on flexible foils, these sensors show resilience to bending deformation for more than 2000 bending cycles and withstand even thermal forming, as relevant for smart wearables and in‐mold electronics. The freedom in the substrate choice and sensor design enabled by dispenser printing allows to implement the proposed sensor technology for different applications focused on touchless interactive platforms, such as advertisement materials, interactive wallpapers, and printed security panels.

Fully Printed Flexible Chemiresistors with Tunable Selectivity Based on Gold Nanoparticles

This study presents a method for printing flexible chemiresistors comprising thin film transducers based on cross-linked gold nanoparticles (GNPs). First, interdigitated silver paste electrodes are printed onto polyimide (PI) foil via dispenser printing. Second, coatings of GNPs and dithiol/monothiol blends are inkjet-printed onto these electrode structures. 1,9-Nonanedithiol (9DT) is used as cross-linking agent and a variety of monothiols are added to tune the sensors’ chemical selectivity. When dosing these sensors with different analyte vapors (n-octane, toluene, 4-methyl-2-pentanone, 1-butanol, 1-propanol, ethanol, water; concentration range: 25–2000 ppm) they show fully reversible responses with short response and recovery times. The response isotherms follow a first-order Langmuir model, and their initial slopes reveal sensitivities of up to 4.5 × 10−5 ppm−1. Finally, it is demonstrated that arrays of printed sensors can be used to clearly discern analytes of different polarity.

Performance comparison between rectangular and trapezoidal-shaped thermoelectric legs manufactured by a dispenser printing technique

At present, device engineering has been limited to the rectangular-shaped TE leg. Therefore, a trapezoidal-shaped leg has been proposed for the TE system and prototypes are developed in this work. Performance comparison has been investigated between rectangular and proposed trapezoidal-shaped leg based TE prototypes. The n-type (0.98Bi,0.02Sb)2(0.9Te,0.1Se)3 and p-type (0.25Bi,0.75Sb)2(0.95Te,0.05Se)3 are considered as base material with Durabond-950 binder material to manufacture TE legs by using a cost-effective dispenser printing technology. The current study includes analysis of SEM imaging, characterization of manufactured TE legs, various experimental tests on TE prototypes, comparison between analytical and experimental results, and cost analyses. For the given restricted volume envelope, the trapezoidal-shaped TE prototype generates 1.24 times more voltage and 1.5 times more power when compared to the rectangular-shaped prototype at 30 °C hot side temperature when the cold side is exposed to the surrounding. For a given constant temperature boundary conditions (i.e., ΔT = 10 °C), the rectangular-shaped TE prototype harvests 1.4 times more power than the trapezoidal-shaped one, while the power density for rectangular TE prototype (i.e., 0.37 W/m3) is almost the same as trapezoidal one (i.e., 0.36 W/m3). Furthermore, the proposed trapezoidal-shaped prototype uses 28.6% less material by mass than the rectangular prototype.

Towards 3D-lithium ion microbatteries based on silicon/graphite blend anodes using a dispenser printing technique.

In this work we present for the first time high capacity silicon/carbon–graphite blend slurries designed for application in 3D-printed lithium ion microbatteries (3D-MLIBs). The correlation between electrochemical and rheological properties of the corresponding slurries was systematically investigated with the prospect of production by an automated dispensing process. A variation of the binder content (carboxymethyl cellulose/styrene–butadiene rubber, CMC/SBR) between 6 wt%, 12 wt%, 18 wt% and 24 wt% in the anode slurry proved to be crucial for the printing process. Regarding the rheological properties increasing binder content leads to increased viscosity and yield stress values promising printed structures with high aspect ratios. Consequently, interdigital 3D-printed micro anode structures with increasing aspect ratios were printed with increasing binder content. For printed 6-layer structures aspect ratios of 6.5 were achieved with anode slurries containing 24 wt% binder. Electrochemical results from planar coin cell measurements showed that anodes containing 12 wt% CMC/SBR binder content exhibited stable cycling at the highest charge capacities of 484 mA h g−1 at a current rate of C/4. Furthermore, at 4C the cells showed high capacity retention of 89% compared to cycling at C/4. Based on this study and the given material formulation we recommend 18 wt% CMC/SBR as the best trade-off between electrochemical and rheological properties for future work with fully 3D-printed MLIBs.

A Printable Paste Based on a Stable n-Type Poly[Ni-tto] Semiconducting Polymer

Polynickeltetrathiooxalate (poly[Ni-tto]) is an n-type semiconducting polymer having outstanding thermoelectric characteristics and exhibiting high stability under ambient conditions. However, its insolubility limits its use in organic electronics. This work is devoted to the production of a printable paste based on a poly[Ni-tto]/PVDF composite by thoroughly grinding the powder in a ball mill. The resulting paste has high homogeneity and is characterized by rheological properties that are well suited to the printing process. High-precision dispenser printing allows one to apply both narrow lines and films of poly[Ni-tto]-composite with a high degree of smoothness. The resulting films have slightly better thermoelectric properties compared to the original polymer powder. A flexible, fully organic double-leg thermoelectric generator with six thermocouples was printed by dispense printing using the poly[Ni-tto]-composite paste as n-type material and a commercial PEDOT-PSS paste as p-type material. A temperature gradient of 100 K produces a power output of about 20 nW.

Laser Treatment as Sintering Process for Dispenser Printed Bismuth Telluride Based Paste.

Laser sintering as a thermal post treatment method for dispenser printed p- and n-type bismuth telluride based thermoelectric paste materials was investigated. A high-power fiber laser (600 W, 1064 nm) was used in combination with a scanning system to achieve high processing speed. A Design of Experiment (DoE) approach was used to identify the most relevant processing parameters. Printed layers were laser treated with different process parameters and the achieved sheet resistance, electrical conductivity, and Seebeck coefficient are compared to tube furnace processed reference specimen. For p-type material, electrical conductivity of 22 S/cm was achieved, compared to 15 S/cm in tube furnace process. For n-type material, conductivity achieved by laser process was much lower (7 S/cm) compared to 88 S/cm in furnace process. Also, Seebeck coefficient decreases during laser processing (40–70 µV/K and −110 µV/K) compared to the oven process (251 µV/K and −142 µV/K) for p- and n-type material. DoE did not yet deliver a set of optimum processing parameters, but supports doubts about the applicability of area specific laser energy density as a single parameter to optimize laser sintering process.

P‐67: Printed Reflective Sloped Wall for Enhancing Luminance of ColorConversion Light Source

We present reflective sloped wall for luminance enhancement of color‐conversion light source consisting of silver epoxy cylindrical line structure and hemispherical lens shaped quantum dot/photo‐curable polymer composite. Dispenser printing method was used to fabricate reflective wall that achieving a 17.39% increase in luminance.

Enabling platform technology for smart fabric design and printing

A hardware and software platform is presented enabling the design, and realisation via printing, of smart fabrics. The cultural and creative industries are an important economic area within which designers frequently utilise fabrics. Smart fabrics offer further creative opportunities to the cultural and creative industries, but designers often lack the required specialist knowledge, in electronics, software and materials, to produce smart fabrics. The software platform offers the ability to perform design, layout and visualisation of a smart fabric using a library of standard smart fabric functions (e.g. electroluminescence) so specialist expertise is not needed. Operation of the smart fabric can be simulated, and parameters can be set for smart fabric control electronics, which consists of standard circuit board modules. The software also provides driver code for the hardware platform to print the smart fabric. The hardware platform consists of a bespoke dispenser printer; functional inks are deposited via a pneumatic syringe controlled by the driver software, allowing bespoke rapid prototyped smart fabrics to be printed. Operation of the software and hardware system is demonstrated by the realisation of an interactive smart fabric consisting of electroluminescent lamps controlled by a proximity sensor. The modular electronics are used to control the smart fabric operation using embedded code generated by the software platform. For example, the blink rate of the electroluminescent lamp can be adjusted by the proximity of a hand. This control is achieved by the use of intuitive drop-down menus and input/output selections by the creative user. At present, the platform allows the design, print and implementation of smart fabrics incorporating the functions of colour change, electroluminescence, sound emission and proximity sensing. The platform can be expanded to add additional functions in the future and the printer will be compatible with new inks developed for screen and inkjet printing.

Fatigue Cycling of Electrical Interconnects Dispensed on Flexible Substrate

Abstract In the presented work, electrical traces were directly printed on 2 mil thick polyimide flexible substrate by a dispenser system using two different silver pastes, SW 1400 paste from Asahi Co. and 125-13 HV paste from Creative Materials Co. The dispenser printing parameters were optimized to achieve the finest possible line width and the printing quality of both materials was investigated. The electrical behavior of the dispensed traces was investigated by monitoring the change in the electrical resistance of the test samples during fatigue cycling at different strains, strain percentage of 1.50%, 2.0%, and 2.5% for different number of cycles up to 1000 cycles. The life time of the dispensed traces versus the applied strain was modeled using Coffin-Manson relation setting 20% change in the initial resistance as the failure criteria. Based on the change in the trace resistance during testing, we concluded that the dispensed SW 1400 silver paste traces were less robust than the dispensed 125-13 HV traces. The finer microstructure, smaller particle size, and shorter inter particles distances of the 125-13 HV silver paste enhanced its durability when subject to fatigue cycling. Moreover, 125-13 HV paste presented better and more uniform printed traces.

An Analysis of a Flexible Dry Surface Electrodes

<p>In the medical field, electrodes are commonly used either to retrieve signals or to conduct current. Most of the off-the-shelf surface electrodes are made from metal or rigid substrates. This paper presents a work on designing a new flexible dry electrodes using poly(3,4-ethylenedioxythiophene) polystyrene sulfonate and silver by means of dispenser printing technology. The polyester cotton fabric was selected as the substrate in this electrode designed. To analyse the new proposed composites of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate and silver, different mixtures have been applied. Results from the experiment show that the conductivity of the proposed flexible electrode is comparable with the commercialized pre-gelled electrode when applied to an electrical stimulator device. Eight out of ten subjects under test described no difference in comfort between the proposed electrodes and pre-gelled electrodes.</p>