Abstract:With the microdroplets of water serving as light scattering particles, the mist flow patterns of round micro-jets can be visualized using the Aerosol Jet ® direct-write system. The visualization images show that the laminar mist jet (with sheath-to-mist ratio Y = 1:1) appears to extend to more than 20 times the diameter of nozzle orifice D for jet Reynolds number Re < 600, especially with D = 0.3 mm and less. For smaller jets (e.g., with D = 0.15 mm), laminar collimated mist flow might be retained to 40xD for … Show more
“…To monitor aerosol density in real time during printing, we designed a printhead with an integrated optical port to enable optical extinction measurements ( Figure a). Previous work to visualize the aerosol stream exiting the print nozzle revealed substantial optical scattering from the micron‐scale droplets, [ 23 ] forecasting the opportunity for quantitative measurements. To test whether this system is sensitive enough to detect variations in the optical density of the aerosol stream, a proof‐of‐concept experiment was performed.…”
Aerosol jet printing is a popular digital additive manufacturing method for flexible and hybrid electronics, but it lacks sophisticated real‐time process control schemes that would enable more widespread adoption in manufacturing environments. Here, an optical measurement system is introduced to track the aerosol density upstream of the printhead. The measured optical extinction, combined with the aerosol flow rate, is directly related to deposition rate and accurately predicts functional materials properties such as the electrical resistance of printed graphene films. This real‐time system offers a compelling solution for process drift and batch‐to‐batch variability, rendering it a valuable tool for both real‐time control of aerosol jet printing and fundamental studies of the underlying process science.
“…To monitor aerosol density in real time during printing, we designed a printhead with an integrated optical port to enable optical extinction measurements ( Figure a). Previous work to visualize the aerosol stream exiting the print nozzle revealed substantial optical scattering from the micron‐scale droplets, [ 23 ] forecasting the opportunity for quantitative measurements. To test whether this system is sensitive enough to detect variations in the optical density of the aerosol stream, a proof‐of‐concept experiment was performed.…”
Aerosol jet printing is a popular digital additive manufacturing method for flexible and hybrid electronics, but it lacks sophisticated real‐time process control schemes that would enable more widespread adoption in manufacturing environments. Here, an optical measurement system is introduced to track the aerosol density upstream of the printhead. The measured optical extinction, combined with the aerosol flow rate, is directly related to deposition rate and accurately predicts functional materials properties such as the electrical resistance of printed graphene films. This real‐time system offers a compelling solution for process drift and batch‐to‐batch variability, rendering it a valuable tool for both real‐time control of aerosol jet printing and fundamental studies of the underlying process science.
“…For a given nozzle diameter, higher sheath-tomist flow rate ratio tends to produce narrower lines. There is an upper limit for the total (sheath plus mist) flow rate through a given nozzle size with a given standoff between nozzle and substrate, due to the requirement of steady laminar mist flow with an impinging jet [6,9]. Therefore, increasing the sheath-to-mist ratio for printing narrower lines would amount to compromising the mass output due to lower mist flow rate, for a fixed mist density generated from the atomizer.…”
Section: Table 1 Parameters Often Used For Producing a Desired Resismentioning
To improve performance and reduce size of printed-circuit board (PCB) in electronics industry, embedding discrete components within a board substrate has been an effective approach by reducing solder joints and their associated impedance mismatching, inductive reactance, etc. With its unique capabilities for non-contact precision material deposition, the Aerosol Jet® direct-write technology has been enabling additive manufacturing of fine-feature electronics conformally onto flexible substrates of complicated shapes. The CAD/CAM controlled relative motions between substrate and print head allows convenient adjustment of the pattern and pile height of deposited material at a given ink volumetric deposition rate. To date in the printed electronics industry, additively printing embedded polymer-thick-film (PTF) resistors has mostly been done with screen printing using carbon-based paste inks. Here we demonstrate results of Aerosol Jet® printed PTF resistors of resistance values ranging from ~50 W to > 1 kW, adjustable (among several variable parameters) by the number of stacked layers (or print passes with each pass depositing a fixed amount of ink) between contact pads of around 1 mm apart with footprint line typically < 0.3 mm. In principle, any ink material that can be atomized into fine droplets of 1 to 5 microns can be printed with the Aerosol Jet® system. However, the print quality such as line edge cleanliness can significantly influenced by ink rheology which involves solvent volatility, solids loading, and so on. Our atomizable carbon ink was made by simply diluting a screen printing paste with a compatible solvent of reasonable volatility, which can be cured at temperatures below 200 oC. We show that Aerosol Jet® printed overlapping lines can be stacked to large pile height (to reduce the resistance value) without significant increase of line width, which enables fabricating embedded resistors with adjustable resistance values in a limited footprint space.
“…top-gated field-effect thin-film transistor 2 . It is specially created for 3D substrates because created narrow aerosol jet ensures printing with nearly identical resolution in the range up to 10 mm from the tip of the nozzle to substrate 3 . This technique enables creating of interconnects of minimal width 8 µm and the same order of magnitude of electrical conductivity as for bulk silver 4 .…”
Section: Introductionmentioning
confidence: 99%
“…It also shows promise for use in various applications, such as coplanar waveguides, antennas, detection electrodes, gates for displays, and collector lines for solar cells 5 – 8 . Due to the development of state of the art in this technique 3 , 9 , 10 , new process modelling approaches 11 and its easy scalability, its application has started not only in research centres but also in commercial production. Figure 1 Aerosol Jet Printing schematics (1) ink atomisation process (2) Mist flow to deposition head caused by atomisation gas flow (3) Jet concentration by sheath gas and deposition on a substrate.…”
Recently, low-cost electronics printed on lightweight, flexible and 3D shaped substrates are gaining importance in the markets of wearables and smart packaging. However, printed electronics do not meet the electrical performance of subtractive techniques because the resistivity of metallic printed patterns is still much higher than that of bulk material. To fulfil this need, low-resistive and easy printable inks for high resolution printed electronics techniques are needed. In this work, parameters of silver nanoparticles ink for micro-scale printed electronics technique, Aerosol Jet Printing, are being enhanced. To increase electrical conductivity and enhance printability, surfactants and dispersing agents were used to increase ultrasonic atomisation efficiency, obtain a uniform structure of printed lines, and narrow the width of printed patterns. Electrical measurements show a decrease in resistivity value in samples enhanced by cationic and non-ionic surfactants, by 95%, compared to initially prepared inks. Surfactant additions to silver nanoparticles Aerosol Jet Printing ink show promising features for application in modern electronics.
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