Aerosol Printing Research Articles

One-step high-speed thermal-electric aerosol printing of piezoelectric bio-organic films for wirelessly powering bioelectronics.

Piezoelectric biomaterials hold a pivotal role in the progression of bioelectronics and biomedicine, owing to their remarkable electromechanical properties, biocompatibility, and bioresorbability. However, their technological potential is restrained by certain challenges, including precise manipulation of nanobiomolecules, controlling their growth across nano-to-macro hierarchy, and tuning desirable mechanical properties. We report a high-speed thermal-electric driven aerosol (TEA) printing method capable of fabricating piezoelectric biofilms in a singular step. Electrohydrodynamic aerosolizing and in situ electrical poling allow instantaneous tuning of the spatial organization of biomolecular inks. We demonstrate TEA printing of β-glycine/polyvinylpyrrolidone films, and such films exhibit the piezoelectric voltage coefficient of 190 × 10-3 volt-meters per newton, surpassing that of industry-standard lead zirconate titanate by approximately 10-fold. Furthermore, these films demonstrate nearly two orders of magnitude improvement in mechanical flexibility compared to glycine crystals. We also demonstrate the ultrasonic energy harvesters based on the biofilms, providing the possibility of wirelessly powering bioelectronics.

Flexible Graphene-Based Sensors for Electrochemical Analysis of Human Saliva and Sweat

Flexible carbon nanomaterial sensors offer a low-cost, facile fabrication approach toward producing sensors at an industrial scale for electrochemical sensing. Graphene and carbon nanotube (CNT) based sensors have been studied, with various fabrication methods available, including producing high-quality thin film graphene and CNTs via chemical vapor deposition (CVD). However, CVD is a high-temperature vacuum process that is low-yielding and consequently costly, hindering its implementation into single-use test strip sensors. Other methods, such as inkjet or aerosol printing, are more cost-effective as they print graphene inks obtained from liquid-phase exfoliation of graphite, which can be performed using large batch processing techniques. Additionally, the laser-induced graphene (LIG) technique directly converts sp3 carbon found in carbon-rich substrates, such as polyimide, into conductive sp2-hybridized carbon found in graphene through a laser scribing technique. Saliva and sweat offer promising biological fluids for precision health monitoring and diagnostics due to the non-invasive nature of their sampling (no need for a blood draw at a laboratory or a fingerstick at home) and due to the abundance of medically relevant analytes. Saliva can also be used for monitoring infections such as COVID-19 infection. Herein, we introduce graphene-based flexible sensors fabricated using scalable manufacturing based on aerosol jet printing (AJP) using custom-formulated graphene inks and laser-induced graphene via direct writing. We report a label-free, high-sensitivity, and rapid-response-time graphene-based electrochemical immunosensor for quantitatively detecting the SARS-CoV-2 Spike Receptor-Binding Domain (RBD) as well as SARS-CoV-2 Spike S1 protein. We demonstrate LIG-based electrochemical sensors for real-time monitoring of glucose, lactate, and sodium in sweat, and potassium and lactate in saliva. Different electrochemical methods are used, including amperometric, potentiometric, coulometric, and impedimetric, to quantify the analytes. All these electrochemical sensors were validated in human saliva and sweat and demonstrated to have limits of detection and linear sensing ranges that are relevant to their sensing applications. Flexibility studies were also performed to evaluate the ability of the sensors to operate under stresses caused by bending, such as those that would be encountered by skin and implanted oral sensors. Results demonstrate the utility of AJP-graphene and LIG for rapid and sensitive measurement of biological analytes and pathogen infection as simple methods for scalable production of non-invasive salivary and perspiration (sweat) health sensors.

Printed and Laser Induced Graphene Electrochemical Biosensors for Rapid Environmental and Biomedical Monitoring

This presentation will demonstrate how low-cost printed and flexible graphene circuits can overcome the challenges associated with conventional electrical circuits to open the door to a highly sensitive monitoring of biochemical threats and toxins including nerve agents/pesticides. The use of inkjet and aerosol printing; spin coating; and laser writing (i.e., laser induced graphene) can be used to create such circuits with high resolution (line widths as low as 20 µm). Moreover, the use of rapid-pulse laser annealing of the printed graphene and/or salt porogens added into graphene inks before printing can be used to further improve the electrical conductivity (< 10 ohms/sq.) and electroactive surface area (nano/micro structuring) of the graphene circuits as well as be used to tune the surface of the printed graphene from one that is hydrophilic (water contact angle (WCA) = 48°) to one that is superhydrophobic (WCA = 158°). More recently we demonstrate how graphene synthesis, patterning and surface wettability can all be controlled through a laser induced graphene (LIG) process that creates a high surface area graphene surface directly from polyimide. Such LIG circumvents the need to create solution-phase graphene inks for printing. These printing and laser fabrication techniques are also amenable for use on flexible and chemically/thermally sensitive surfaces including polymers and paper.Moreover, the laser etched printed graphene and LIG exhibits an inherent 3D morphology that significantly increases the electrode electroactive surface over traditional 2D planar graphene electrodes. This large increase in surface area significantly improves the loading of enzyme onto the electrode surface and subsequently increases the heterogenous charge transport during catalytic pesticide sensing. Such ion sensors displayed near-Nernstian sensitivities, wide sensing ranges over four orders of magnitude extending from the 10–2 M down to detection limits in the 10–6 M range or for fertilizer ions (nitrate, ammonium, potassium, calcium, and magnesium) reaching down to detection limits less than 1 ppm in some cases in soil and water samples. The pesticide sensing capability of the sensor is able to reach an extremely low picomolar detect limit for organophosphates (paraoxon) and to the nanomolar regime for neonicotinoids in surface waters. We also demonstrate how this flexible LIG electrodes can be coupled with polymeric microfluidics and adhered to the body for continuous monitoring of lactate, glucose, and sodium in the sweat. Finally, we demonstrate how such surface wettability patterning of the printed graphene and LIG itself through laser etching can be used to make hydrophilic LIG tracks surrounded by near superhydrophic sidewalls for open microfluidic fluid transport without the need for polymeric microfluidics. Such open microfluidic tracks enable the splitting and transport of fluid samples to distinct electrochemical sensors for multiplexed biosensing of both fertilizer ion and pesticide monitoring from water samples and assist in harvesting sprayed pesticides in the field. Figure 1

Analysis and Modeling of Line Width of Aerosol Printing based on Image Processing

This article proposes a method for calculating the line width of aerosol printing based on image processing and analyzes the line width results obtained using this method, aiming to establish an accurate mathematical model between parameters and line width. This article conducts experiments using carrier gas and sheath gas as parameters in aerosol printing and uses an industrial camera to characterize the printed lines. The line images are processed in MATLAB to obtain high-precision printed line widths. Analyzing the line width data after image processing, it was found that the line width increased with the increase of carrier gas and decreased with the increase of sheath gas. Then, using the discovered regularity, mathematical relationships between sheath gas and line width, and carrier gas and line width are established. The calculation method of print line width used in this article is highly accurate and efficient and establishes a functional relationship analysis model that can accurately describe the relationship between variables and line width, guiding printing-specific line widths.

Analysis of different printing technologies for metallization of crystalline silicon solar cells

Abstract Crystalline silicon solar cells have been the workhorse of the Solar Photovoltaic industry, contributing to &gt;90% of the total installations. The fabrication of solar cells involves multi-process steps i.e. chemical treatment, diffusion, passivation and metallization. Among these process steps of solar cell manufacturing, metallization is the most critical one since it not only influences cell performance but also the cost of manufacturing to a great extent. A proper metallization process essentially helps in reduction of various electrical and optical losses. A lot of research is being carried out on various metallization technologies to arrive at an efficient, cost-effective solution for contact formation. Screen printing, flexographic printing, laser metal sintering and recently developed 3D printing are some of the technologies of interest in this field. While 3D printing, laser metal sintering, etc. are still at lab level, flexographic and gravure printing are in search of a suitable paste which can make the technology production-worthy. It is the screen-printed technology of solar cells that currently dominates the commercial market because of its low production cost and process simplicity. Amongst the several technologies that have been developed till date for cell metallization, the screen-printing technology promises to be the most reliable, rugged and production-worthy technology. In this paper, different metallization technologies viz. screen printing (conventional, knotless), stencil printing, light induced plating, metal sintering, flexographic printing, aerosol printing etc. used for contact formation in high efficiency silicon solar cells have been reviewed.

Atmospheric pressure glow discharge plasma sintering of solvent-free silver lines made by laser ablation dry aerosol printing

Atmospheric pressure glow discharge plasma sintering of solvent-free silver lines made by laser ablation dry aerosol printing

High-Performance Flexible Piezoresistive Pressure Sensor Printed with 3D Microstructures.

Flexible pressure sensors have been widely used in health detection, robot sensing, and shape recognition. The micro-engineered design of the intermediate dielectric layer (IDL) has proven to be an effective way to optimize the performance of flexible pressure sensors. Nevertheless, the performance development of flexible pressure sensors is limited due to cost and process difficulty, prepared by inverted mold lithography. In this work, microstructured arrays printed by aerosol printing act as the IDL of the sensor. It is a facile way to prepare flexible pressure sensors with high performance, simplified processes, and reduced cost. Simultaneously, the effects of microstructure size, PDMS/MWCNTs film, microstructure height, and distance between the microstructures on the sensitivity and response time of the sensor are studied. When the microstructure size, height, and distance are 250 µm, 50 µm, and 400 µm, respectively, the sensor shows a sensitivity of 0.172 kPa−1 with a response time of 98.2 ms and a relaxation time of 111.4 ms. Studies have proven that the microstructured dielectric layer printed by aerosol printing could replace the inverted mold technology. Additionally, applications of the designed sensor are tested, such as the finger pressing test, elbow bending test, and human squatting test, which show good performance.

Process-Recipe Development for Printing of Multilayer Circuitry With Z-Axis Interconnects Using Aerosol-Jet Printed Dielectric Vias

Abstract Flexible electronics is emerging as a new consumer-industry phenomenon. The promise of additively printed flexible electronics has sparked interest in a detailed understanding of the parameters and interactions of the printing process with the realized performance. Aerosol Jet printing technology has garnered increased interest, owing to a noncontact nature of print process and the high standoff allowing for printing on nonplanar surfaces. Prior efforts with aerosol-jet printing have focused on single-layer substrates. The current efforts focus on higher end printed circuit boards designs, which may need multilayers, with multilayer stacking of interconnections and z-axis connections through vias. The results presented in the paper attempt to address the need for process recipes for multilayer circuits and z-axis interconnects. Aerosol printing method has been shown to have wide compatibility with wide array of inks such as silver, copper, and carbon. Realization of high-volume scale-up of the process needs process recipes with statistical assessment of process stability and variance. In this paper, z-axis interconnects have been realized with the help of Aerosol printable silver ink and dielectric polyimide ink. The interaction of the sintering profile and the realized conductivity and shear load value of the printed conductive metal layers has been presented for each of the additional layers. Additive build-up processes may need successive exposure to temperature for the purpose of sintering. The downstream-printed conductive lines would undergo different sintering conditions and would then be tested for parameters such as interconnect resistance and shear load to failure. This paper explores the printing of multilayer up to eight conductive layers. Sintering profile for lower resistance per unit length and higher shear load to failure was tested.

Dry Printing and Additive Nanomanufacturing of Flexible Hybrid Electronics and Sensors

AbstractThe growing demand for flexible and wearable hybrid electronics has triggered the need for advanced manufacturing techniques with versatile printing capabilities. Complex ink formulations, use of surfactants/contaminants, limited source materials, and the need for high‐temperature heat treatments for sintering are major issues facing the current inkjet and aerosol printing methods. Here, the nanomanufacturing of flexible hybrid electronics (FHE) by dry printing silver and indium tin oxide on flexible substrates using a novel laser‐based additive nanomanufacturing process is reported. The electrical resistance of the printed lines is tailored during the print process by tuning the geometry and structure of the printed samples. Different FHE designs are fabricated and tested to check the performance of the devices. Mechanical reliability tests including cycling, bending, and stretching confirm the expected performance of the printed samples under different strain levels. This transformative liquid‐free process allows the on‐demand formation and in situ laser crystallization of nanoparticles for printing pure materials for future flexible and wearable electronics and sensors.

Aerosol Dry Printing for SERS and Photoluminescence-Active Gold Nanostructures Preparation for Detection of Traces in Dye Mixtures.

We proposed a novel method of nanostructure preparation for observation of surface-enhanced Raman spectroscopy (SERS) and metal-enhanced fluorescence (MEF) based on the deposition of gold nanoparticles (GNPs) above the thin dye film by dry aerosol printing. We detected various enhanced SERS and MEF signals of films of malachite green (MG) and rhodamine B (RhB) mixtures, depending on the surface packing density of Au NPs on the strip, and found the optimum one to achieve the 3.5 × 105 SERS enhancement. It was shown that statistical methods of chemometrics such as projection on latent structures provided the opportunity to distinguish SERS of MG from 100 ppm RhB in a mixture, whereas separation of MEF signals are feasible even for a mixture of MG and 1 ppm RhB due to two-photon excitation.

Formation of planar plasmon microstructures by dry aerosol printing

Optical properties and microstructure of samples formed by dry aerosol printing are studied. Silver nanoparticles flat layers of two types were formed on substrates surfaces and were investigated by a spectrophotometer, a scanning electron microscope, and a transmission electron microscope. It is shown that all microstructures support plasmon resonance on individual nanoparticles with the Q factor depending both on the width of the nanoparticles size distribution in the aerosol and on their tendency to agglomeration and aggregation.

Laser sintering of oxidized copper nanoparticles deposited by dry aerosol printing

Sintering of oxidized copper nanoparticles arrays in the form of lines by the local treatment of laser radiation with wavelengths of 527 nm and 980 nm was studied. To form lines with a width equal to 40–150 μm and a thickness equal to 0.5–4 μm focused aerosol jets with average nanoparticle sizes of 110 and 65 nm were used. The production of semiconductor arrays from oxidized copper nanoparticles with a specific electrical resistance of 2⋅10−3 Ω⋅m using laser radiation with a wavelength of 980 nm was demonstrated.

Aerosol printing and flash sintering of conformal conductors on 3D nonplanar surfaces

Printing techniques have been extensively studied as a promising route towards large-scale, low-cost and high-throughput manufacturing process for electronic devices. With the recently emerging applications in wearable electronics and customizable conformal electronics, it calls for the necessity to develop printed electronics that function on complex, 3D nonplanar architectures. In this study, aerosol printing and flash sintering of conformal conductors on nonplanar surfaces are demonstrated. Various printed patterns are fabricated by aerosol printing of conductive ink by copper nanoparticles (Cu NPs) on both planar and nonplanar surfaces. Pulsed flash light introduces rapid sintering of the printed Cu patterns in the ambient environment. For the nonplanar patterns, a back reflector is utilized to improve the uniformity of sintering. As a result, highly conductive customizable nonplanar Cu patterns with conductivity at 10%–12% of that of bulk Cu are obtained. Effects of different sintering conditions, including sintering voltage and mounting distance on the conductivity of sintered patterns are studied. For nonplanar patterns, conductivity values at different localized spots on the nonplanar rod are also investigated to evaluate the uniformity of nonplanar sintering. The processes of aerosol printing and flash sintering have provided a facile manufacturing route for conformal conductors on arbitrary nonplanar objects.

Physicochemical regularities in highly filled polyaluminosilicate applied on aluminum base by 3D aerosol printing

A modified technique has been used to synthesize a highly filled polyaluminosilicate with a controlled supramolecular structure during its applying on an aluminium base by 3D aerosol printing. It has been found how the pH medium affects the polyaluminosilicate ability to form fractal supramolecular formations. Methods to control the highly filled polyaluminosilicate structure directly along the aluminium base surface have been found.

Additive Manufacturing of Sandwich–Structured Conductors for Applications in Flexible and Stretchable Electronics

Additive manufacturing methods have shown great potentials to substitute the costly and time‐consuming conventional subtractive methods in the processing of electronically conductive materials for applications in flexible and stretchable electronics. Herein, additive manufacturing of highly conductive, sandwich‐structured conductors with high‐temperature processibility and versatility in applicable substrates is reported. The sandwich‐structured conductors with silver nanoparticles (Ag NPs) as electronic conductors and polyimide (PI) as encapsulation are layer‐by‐layer deposited by aerosol printing into PI/Ag/PI composites. A high annealing temperature of 250 °C contributes to the high electronic conductivity of the Ag layer at 1.14 × 107 S m−1, which is in the same order of magnitude to the conductivity of bulk Ag at 6.3 × 107 S m−1. The high annealing temperature also significantly improves the interfacial bonding between the Ag and PI layers. For applications in flexible and stretchable electronics, the sandwich‐structured conductors are transferrable to various substrates through a thiol−epoxy bonding process, including polystyrene (PS), polyethylene terephthalate (PET), Kapton, and polydimethylsiloxane (PDMS) thin films. The sandwich‐structured conductors transferred to flexible and stretchable substrates exhibit highly retained electronic conductivity under deformations such as bending and stretching.

Toward all aerosol printing of high-efficiency organic solar cells using environmentally friendly solvents in ambient air

Aerosol-printed organic solar cells based on PTQ10:Y6-BO achieve a power conversion efficiency (PCE) of 15.65%. Three functional layers are printed continuously on a convey belt, and the all-aerosol-printed cells reach a PCE up to 14.78%.

The study of radiation attenuation in disordered silver nanoparticles arrays formed by dry aerosol printing

The interaction processes of continuous laser radiation with wavelengths 527 and 980 nm with disordered arrays of spherical silver nanoparticles formed by dry aerosol printing are studied. The arrays were deposited on a glass substrates in the form of lines of various thickness and differed in the mean sizes of nanoparticles. It is shown that the radiation attenuation by arrays with disordered nanoparticle structure depends on the optical effects both on isolated spherical nanoparticles and on nanoparticle agglomerates.

The influence of the morphology of oxidized copper nanoparticles on the electrical properties of microstructures obtained by dry aerosol printing

The influence of the morphology of oxidized copper nanoparticles on the deposition efficiency, packing density, and resistivity of microstructures obtained by dry aerosol printing was studied. It has been established that the thermal treatment of aerosol nanoparticles allows to vary their morphology from branched submicron agglomerates to compact spherical nanoparticles with a size of 20-50 nm. It is shown that the use of spherical nanoparticles in comparison with agglomerates allows one to obtain densely packed nanoparticles on substrate. Moreover, obtaining of semiconductor microstructures from oxidized copper nanoparticles on a plastic substrate with a resistivity of 0.01 Ohm • m was demonstrated.

Basic laws of filled polyaluminosilicate polycondensation used in printed circuit boards of power electronic spacecraft devices

Filled fractal aluminosilicates have been synthesized by a sol-gel method. Optimal conditions to obtain aluminosilicate gels have been determined. The obtained samples have been studied by IR spectroscopy, X-ray phase analysis, transmission electron microscopy, and the du Nouy method. The studies have shown the presence of chemically unbound –OH groups in the aluminosilicates. The effect of the amount of polymer matrix filled with highly dispersed filler powder and medium acidity on the adhesive strength of the dielectric layers applied on aluminum bases by 3D aerosol printing used in printed circuit boards of power electronic spacecraft devices has been studied by means of the du Nouy method.

Comparison of Laser Sintering of Silver Nanoparticles in Form of Microdroplets of Nanoink and Dry Nanoparticles Obtained in a Gas Discharge

This article presents a comparison of laser sintering of deposited nanoparticles obtained by two methods of aerosol jet printing. The first printing method was based on the use of silver nanoparticles in the form of microdroplets contained in nanoink. In the second method, dry nanoparticles were obtained as a result of gas-discharge synthesis without the use of solvents. The nanoparticles in both experiments were deposited on a glass substrate in the form of a line with a width of about 50 ± 5 μm and a height of about 1.0 ± 0.2 μm. Then, the obtained lines were sintered using laser radiation with a wavelength of 1064 nm. As a result of experiments on the deposition and sintering, it was found that the electrical resistivity of the lines of sintered nanoparticles in the form of nanoink and dry nanoparticles obtained in a gas discharge was 8.1 and 4.9 μΩ·cm, respectively. Thus, it has been demonstrated that laser sintering of nanoparticles obtained in a gas discharge makes it possible to achieve a lower specific resistance of lines than the method of aerosol printing using nanoink. In addition, the electrical resistivity of the lines of sintered nanoparticles obtained in a gas discharge is 3 times greater than the electrical resistivity of bulk silver, which is a sufficient result for the creation of conductive elements of printed electronics.