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As Aerosol Jet® (AJ) printing is becoming more attractive to additive manufacturing, printed electronics, among other applications, reducing or minimizing the amount of ink droplets landing in unintended regions—known as the overspray—has been elevated on the agenda for print quality control and improvement. Many AJ users had discussed the overspray issue associated with AJ printing, while the metrology for quantified evaluation of overspray is still lacking. In this work, the likely physical mechanism for inducing overspray is analyzed along with a set of computational fluid dynamics (CFD) simulations. We then present a 2D image processing method for quantitatively evaluating the severity of overspray in terms of its percent area coverage versus a normalized distance from printed line edge. Our results show that the amount of overspray of AJ printing seems to scale with the printed line width (LW), and usually to become negligible (e.g. percent area coverage of overspray < 1%) beyond 30%–40% of LW from line edges. The overspray is shown to often decrease by increasing the jet velocity and sheath-to-mist ratio. Without loss of generality and for concise illustration, herewith we use only one representative ink to print test samples for the quantitative overspray analysis. The results have been found to bear a resemblance to AJ printed features with many other inks.

Aerosol jet printing offers a versatile, high-resolution digital patterning capability broadly relevant to flexible and printed electronic systems. Despite its promise and numerous demonstrations, the theoretical principles driving process outputs have not been thoroughly explored. Here a custom-built, modular printing system is developed to provide a head-to-head comparison of two print nozzle geometries to better understand the technology. Print resolution data from a range of process parameters are analyzed using a support vector machine framework. The linear deposition rate is identified as a key variable, which can confound careful studies of printing performance. Taking this into account, a clear difference is observed between the printheads, corresponding to a difference in resolution of 57% ± 11% under typical conditions. Models to understand differences in aerodynamic and mass transport effects identify enhanced drying within a large diameter printhead as a likely cause of this difference. Overall, this study provides improved understanding of the aerosol jet printing process, including valuable insight to inform process optimization, robust data analysis, ink formulation, and printer geometric design.

Printing is a promising method to reduce the cost of fabricating biomedical devices. While there have been significant advancements in direct-write printing techniques, non-contact printing of biological reagents has been almost exclusively limited to inkjet printing. Motivated by this lacuna, this work investigated aerosol jet printing (AJP) of biological reagents onto a nonfouling polymer brush to fabricate in vitro diagnostic (IVD) assays. The ultrasonication ink delivery process, which had previously been reported to damage DNA molecules, caused no degradation of printed proteins, allowing printing of a streptavidin-biotin binding assay with sub-nanogram ml-1 analytical sensitivity. Furthermore, a carcinoembryogenic antigen IVD was printed and found to have sensitivities in the clinically relevant range (limit of detection of approximately 0.5 ng ml-1 and a dynamic range of approximately three orders of magnitude). Finally, the multi-material printing capabilities of the aerosol jet printer were demonstrated by printing silver nanowires and streptavidin as interconnected patterns in the same print job without removal of the substrate from the printer, which will facilitate the fabrication of mixed-material devices. As cost, versatility, and ink usage become more prominent factors in the development of IVDs, this work has shown that AJP should become a more widely considered technique for fabrication.

We investigate and optimize the Aerosol Jet Printing of PEDOT:PSS by studying the role of the parameters determining the final quality of the printed features. In fact, printing thin films of organic materials requires a high control in the deposition process to control the morphology/structure of the films that determine the electrical and functional performance of organic devices. We studied aerosol jet printed lines of the PEDOT:PSS semiconductive polymer on flexible Kapton substrates. We choose the focus ratio, defined as the ratio between the sheath and carrier gas flow rates, as the main parameter that best characterizes the process and hence the characteristics of printed lines. A detailed analysis of the line width and thickness, as a function of the focus ratio and carrier gas flow for different nozzle sizes and sheath gas flow rates, is reported. The edge profile definition of printed PEDOT:PSS lines has been found to be affected by a combination of overspray, typical of aerosol deposition, and pinholes due to the Kapton/PEDOT:PSS interaction, while their core profile results to be almost defects free. An optimal printing window for different nozzle sizes has been determined in terms of a minimization of overspray/pinholes effects with respect to the whole line width. Finally, an array of whole-plastic, planar Organic Electrochemical Transistors, having both the channel and the gate electrode made of PEDOT:PSS, has been manufactured using the best combination of process parameters. Transistors have been characterized for different channel/gate area ratios and the transconductance analysed as a function of channel to gate area.

The study on dry aerosol jet printing with simultaneous sintering of deposited Ag nanoparticles 20-80 nm in size on a heated plastic substrate is presented. It is established that to achieve minimal electrical resistivity of microstructures produced of ~200 μΩcm, the recommended temperature of the heated substrate is to be ~200 °C. It is also found that when increasing the heated substrate temperature above 225 °C, formed microstructure electrical resistivity rises abruptly due to plastic substrate deformation. The result obtained is of interest in developing a one-step technology for producing electronic components on a plastic substrate.

Aerosol jet printing (AJP) is a promising microscale additive manufacturing technology for emerging applications in printed and flexible electronics. However, the more widespread adoption of this emerging technique is hindered by a limited fundamental understanding of the process. This work focuses on a critical and underappreciated aspect of the process, the interaction between drying induced by the sheath gas and impaction. Combining focused experiments with support from numerical modeling, it is shown that these effects have a dramatic impact on key outputs of the process, including deposition rate, resolution, and morphology. These effects can amplify minor changes in ink composition or atomization yield, increasing process sensitivity and drift. Moreover, these effects can confound strategies for in-line process monitoring and control based on empirical observables. Strategies to directly manipulate this annular drying phenomenon are presented, providing a viable tool to tailor and study the process. This work clarifies coupled effects of printer design, ink formulation, and print parameters, establishing a more robust theoretical framework for understanding the AJP process and advancing the maturity of this promising technology.

Aerosol jet is an additive manufacturing technique that writes electronic inks directly onto the surface. The process has great potential for printed electronics as it is non-contact method that works well with variety of materials- metals, insulators, semiconductors, epoxy and encapsulation materials for conformal writing. This paper explores the effect of some parameters like ultrasonic power and atomizer flow on overall print quality, thus establishing a process window. Published version