Efficient Sonochemistry through Microbubbles Generated with Micromachined Surfaces

TL;DR

This paper presents a microfabricated sonochemical reactor with controlled microbubble nucleation sites, significantly improving efficiency and chemical effects in water treatment and synthesis processes.

Contribution

The study introduces a novel microfabrication-based reactor design that precisely controls bubble nucleation, enhancing sonochemical efficiency at industrially relevant scales.

Findings

Increased sonochemical efficiency by controlling bubble nucleation sites.

Significant enhancement of chemical effects at the same power levels.

Microbubbles can be generated continuously for hours without depleting gas content.

Abstract

Sonochemical reactors are used in water treatment, the synthesis of fine chemicals, pharmaceutics and others. The low efficiency of sonoreactors have prevented its massive usage at industrial scales. Controlling the appearance of bubbles in place and time is the most limiting factor. A novel type of sonochemical reactor was designed making use of micro-fabrication techniques to control the nucleation sites of micro-bubbles. The efficiency was increased first by locating the nucleation sites in the most active region of a micro-chamber; additionally the desired chemical effect was significantly higher at the same powers than when not controlled. Silicon substrates were micromachined with "artificial nucleation sites" or pits, and placed at the bottom of the micro-chamber. The pits entrap gas which, upon ultrasonic excitation, sheds off a stream of microbubbles. The gas content of the pits is not depleted but is replenished by diffusion and the emission of microbubbles can continue for hours.