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Speaker 1: Welcome to brain Stuff from How Stuff Works pay brain Stuff.

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Speaker 1: I'm Lauren Vogelbaum, and I'm here today to tell you

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Speaker 1: that Harvard University has announced that its researchers have developed

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Speaker 1: a way to print objects using sound as the delivery system,

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Speaker 1: called acoustophoretic printing. The method, according to their press release quote,

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Speaker 1: could enable the manufacture of many new biopharmaceuticals, cosmetics, and food,

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Speaker 1: and expand the possibilities of optical and conductive materials. Let's

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Speaker 1: unpack all that printing with liquid such as ink has

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Speaker 1: become a way of life thanks to the ink jet

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Speaker 1: printing process. But what if instead of ink, you wanted

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Speaker 1: to print living cells or other biological materials. What if

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Speaker 1: you wanted to print liquid metal with ink jets. The

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Speaker 1: ability of a printer to pull a substance out of

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Speaker 1: a nozzle grinds to a halt as that substance becomes thicker.

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Speaker 1: But now the team of scientists at Harvard has announced

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Speaker 1: significant progress in the creation of sound fields that can

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Speaker 1: pull viscous substances, much as liquid metal or living cells

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Speaker 1: from the nozzle of a printer. It begins with gravity.

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Speaker 1: Simple gravity is what causes liquid to drip. How fast

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Speaker 1: or how often it drips depends on its viscosity, that's,

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Speaker 1: its thickness and its resistance to shearing and tensile stresses. Water,

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Speaker 1: for example, is far less viscous than coin syrup. Coin

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Speaker 1: syrup is far less viscous than honey. The more viscous

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Speaker 1: that a fluid is, the longer it takes for gravity

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Speaker 1: to produce a droplet. Printing systems, such as in chip printing,

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Speaker 1: typically use a droplet method of transferring a liquid material

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Speaker 1: like ink onto a medium like paper. The more viscous

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Speaker 1: a material is, however, the more difficult it is to

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Speaker 1: manipulate for printing. Daniel Feresti, a research associate in material

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Speaker 1: science and mechanical engineering at Harvard, said, our goal was

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Speaker 1: to take viscosity out of the picture by developing a

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Speaker 1: printing system that is independent from the material properties of

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Speaker 1: the fluid. And this is where sound comes in. Foresti

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Speaker 1: and his fellow researchers and experimenting with the pressures of

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Speaker 1: sound waves on liquids. In order to give gravity a boost,

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Speaker 1: They built a sub wavelength acoustic resonator. It's designed to

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Speaker 1: produce tightly controlled acoustic fields that effectively increase the relative

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Speaker 1: gravity at the printing nozzle. According to the release, the

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Speaker 1: researchers have been able to generate pulling forces one times

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Speaker 1: the gravitational forces that a printer nozzle would normally experience

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Speaker 1: here on Earth. That amount of force also happens to

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Speaker 1: be more than four times the gravity that a printer

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Speaker 1: nozzle would experience on the Sun. At that point, the

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Speaker 1: size of the droplet is determined by the amplitude of

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Speaker 1: the sound wave. The higher the amplitude, the smaller the drop. First,

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Speaker 1: he said, the idea is to generate an acoustic field

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Speaker 1: that literally detaches tiny droplets from the nozzle, a much

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Speaker 1: like picking apples from a tree. A wide range of

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Speaker 1: materials have been used to test this new printing method,

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Speaker 1: including honey stem cell inks, biopolymers, optical resins, and liquid metals.

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Speaker 1: Doctor Jennifer Lewis, a professor of biologically inspired engineer RING

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Speaker 1: at Harvard, stated, our technology should have immediate impact on

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Speaker 1: the pharmaceutical industry. However, we believe that this will become

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Speaker 1: an important platform for multiple industries. Today's episode was written

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Speaker 1: by Jared W. Alexander and produced by Tyler Clang. To

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Speaker 1: find brain Stuff merch hoodie for fall. Maybe check out

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Speaker 1: our shop at t public dot com, slash brain stuff,

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Speaker 1: and of course, for more on this and lots of

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Speaker 1: other topics with a lot of gravity, visit our home planet,

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Speaker 1: how stuff works dot com