New printer uses sound waves to shape ink droplets

sound can be used to print droplets that could not be printed before

Recently, researchers at Harvard University have discovered a new printing technique that uses sound waves to generate droplets from waves, which occur with an unprecedented range of structure and viscosity. This technique can finally enable the creation of many new biopharmaceuticals, cosmetics, and food and expand the possibilities of optical and conductive materials, and this printing method can be used for drop-on-demand printing. In acoustophoretic printing, the sound waves produce a controlled force that pulls each drop out of the nozzle when it reaches a specific size and removes it toward the printing target - like picking apples from a tree!

At present, liquid droplets are used in many applications from printing inks on paper to create microcapsules for drug delivery. Inkjet printing is the most common technique used for liquid droplets of patterns, but it is only suitable for liquids that are nearly ten times more sticky than water. Yet for many researchers, many of the fluids of interest are more sticky. For example, biopolymers and cell-laden solutions, which are important for biopharmaceuticals and bioprinting, are at least 100 times more sticky than water. Some Chinese-based biopolymers can be sticky in the form of honey, which is 25,000 times more sticky than water. The viscosity of these liquids also dramatically changes with temperature and structure, making it even more difficult to optimize printing standards to control the size of the droplets.

"By using the acoustic forces, we have created a new technology that enables the inventory of printing of numerous materials to be printed in a drop-on-demand manner, said Jennifer Lewis, the Hansjorg Wyss Professor of Biologically Inspired Engineering at the Harvard John A. Paulson School of Engineering and Applied Sciences."Our technology should have an immediate effect on the pharmaceutical industry. However, we believe that it will become an important platform for many industries.

"Our goal was to develop viscosity of the picture by developing a printing system which is free, the physical properties of the fluid," said Daniele Foresti, first author of the paper, the Branco Weiss Fellow and Research Associate in Materials Science and Mechanical Engineering at SEAS. "Thanks to gravity, any liquid drip-from water leaking from the tap to the experience of pitch drop throughout the century. With gravity alone, droplets are still large and difficult to control. The temperature, which has a viscosity of nearly 200 billion times the water, makes one drop in each decade. To enhance the formation of projection, the research team relies on generating sound waves. These pressure waves have typically been used to challenge gravity, as is the case in acoustic altitude. Now, used by researchers to help gravity, dubbing this new technique of audio printing".

"Researchers have developed a new printing platform using acoustic forces, which, unlike other methods, are independent of materials, thus providing multiple uses for printing. The application space is limitless. This is a great example of the breadth and reach of collaborative research, said Dan Finotello, director of NSF's MRSEC program. "The researchers built an acoustic resonance with an underwater length that could generate a very limited acoustic field, resulting in a pull force exceeding 100 times the normal gravitational force (G 1) at the tip of the printer nozzle - more than four times the gravitational force on the sun's surface. This controllable force pulls every drop of a nozzle when it reaches a certain size and directs it toward the printing target. The greater the amplitude of sound waves, the fewer droplets, regardless of the viscosity of the liquid. The researchers tested the process on a wide range of materials from honey to stop cell inks, optical resins, biopolymers, and even liquid metals. Most importantly, sound waves do not pass through droplets, making this method safe to use even with sensitive biological charges, such as living cells or proteins. As mentioned above, acoustic waves were previously used to raise liquid droplets. The latest technology uses sound waves to enhance gravity rather than help. The formation of normal low and normal droplets leads to small capsules being very large and high. By pushing droplets more efficiently, scientists can produce smaller, more precise deposits. The greater the sound waves, the smaller the droplets, Dan Finotello explained.

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This story is published in Science Advances, 2018, with the title “Acoustophoretic printing” and distributed by many websites with the title "Sound can be used to print droplets that couldn't be printed before."

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