Creating Precise Patterns from Microscopic Particles Using Sound

Researchers can move microscopic particles and droplets into precise patterns by harnessing the power of sound in air. The implications for printing, especially in the fields of medicine and electronics, are far-reaching.

The scientists from the Universities of Bath and Bristol have shown that it’s possible to create precise, pre-determined patterns on surfaces from aerosol droplets or particles, using computer-controlled ultrasound.

This work could revolutionize printing, improving the speed, cost, and precision of non-contact patterning techniques in air. Their work already shows the potential of sonolithography for biofabrication.

Advanced Materials – Sonolithography: In‐Air Ultrasonic Particulate and Droplet Manipulation for Multiscale Surface Patterning

Acoustic fields are increasingly being used in material handling applications for gentle, noncontact manipulation of particles in fluids. 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. The technique capitalizes on inexpensive, commercially available transducers and electronics. 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.

Acoustophoretic techniques are increasingly recognized for their capabilities in noncontact particle manipulation. Standing acoustic pressure fields generated by one or more transducers contain regular distributions of high‐pressure regions (antinodes) and zero‐pressure regions (nodes).

Acoustic patterning techniques are particularly appealing for biotechnological applications due to the noncontact handling, relatively low power requirements as compared to optical tweezers, and no need for chemical or physical modifications to cells.

Acoustic technologies for handling particles in air typically use frequencies in the low ultrasonic range due to the rapidly increasing attenuation with increasing frequency. In‐air ultrasonic standing wave devices have mainly been used for containerless processing or analysis. Acoustic aerosol concentrators have been developed. Applications for making patterned surfaces have been limited.

Now they introduce basic principles and techniques of sonolithography, an air‐based acoustophoretic method for creating patterned surfaces from both aerosolized droplets and solid particulates. Prospective applications include production of patterned surfaces that can give rise to localized material properties, or convey additional functionality to a substrate, as well as generate hierarchical structuring or form the basis of composites or metamaterials.In biofabrication, precisely positioned proteins and bioactive molecules can mimic the instructional cues of the native extracellular matrix (ECM), which provides both physical support and spatiotemporal regulation of various biophysical signals, thus influencing cellular behaviors. We apply sonolithography to biofabrication, showing its efficacy in providing defined regions for cell adhesion on a substrate, and indicating its potential use as a method for directly positioning mammalian cells. Sonolithography is also shown to pattern a variety of materials and substrates.

SOURCES- Bath University, Advanced Materials
Written by Brian Wang,