Printing with the power of ultrasound

Scientists from the Universities of Bath and Bristol have shown that it is possible to create precise, predetermined patterns on surfaces from aerosol droplets or particles, using computer-controlled ultrasound. Dubbed ‘sonolithography’, the technique is expected to have far-reaching implications for printing — especially in the fields of medicine and electronics.

“The power of ultrasound has already been shown to levitate small particles,” said Bath’s Professor Mike Fraser, who served as corresponding author on the study. “We are excited to have hugely expanded the range of applications by patterning dense clouds of material in air at scale and being able to algorithmically control how the material settles into shapes.”

Writing in the journal Advanced Materials Technologies, the study authors explained, “Sonolithography is based on the application of acoustic radiation forces arising from the interference of ultrasonic standing waves to direct airborne particle/droplet accumulation in defined spatial regions. This approach enables reliable and repeatable patterning of materials onto a substrate to provide spatially localized topographical or biochemical cues, structural features, or other functionalities that are relevant to biofabrication and tissue engineering applications.

“Sonolithography is capable of rapidly patterning micrometer to millimeter scale materials onto a wide variety of substrates over a macroscale (cm²) surface area and can be used for both indirect and direct cell patterning,” the authors continued, noting that the technique capitalises on inexpensive, commercially available transducers and electronics.

The researchers believe their work could revolutionise printing, improving the speed, cost and precision of non-contact patterning techniques in air. They are keen to develop the technique for use in printed electronics — with sonolithography being used to arrange conductive inks into circuits and components — as well as in biofabrication.

“Sonolithography enables gentle, non-contact and rapid patterning of cells and biomaterials on surfaces,” said Bristol’s Dr Jenna Shapiro, lead author on the study. “Tissue engineering can use biofabrication methods to build defined structures of cells and materials. We are adding a new technique to the biofabrication toolbox.”

“The objects we are manipulating are the size of water drops in clouds,” added co-author Professor Bruce Drinkwater, also from Bristol. “It’s incredibly exciting to be able to move such small things with such fine control. This could allow us to direct aerosol sprays with unheard of precision, with applications such as drug delivery or wound healing.”

Image caption: Ultrasound and computer algorithms control how material settles into shape.

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