Freeform Etching of Microchannels in Hydrogels by Ultrasonic Cavitation

With structural similarities to biological tissues, hydrogels offer many potential applications in biomedicine. To improve hydrogel perfusion, simple microchannels can be fabricated using a variety of templating and printing approaches, but the formation of interconnected, winding, and branching channels remains a significant challenge. The cavitation-mediated etching of microchannels in agarose hydrogels is demonstrated. An ultrasonic cavitation transducer coupled with a motorized control system is used to enable the formation of consistent microchannels within the agarose hydrogels with ellipsoid cross-sectional areas and uniform widths on the order of 244 ± 19.5 μm. With increasing transducer voltage, the average microchannel width increases, while higher positional translation speed results in shorter dwell times and, therefore, smaller microchannels. Infusion of fluorescent dyes indicates little turbulence within the microchannels formed by the cavitation etching process. This technique can fabricate branched and complex microchannel paths. Furthermore, the mechanical and swelling properties of hydrogels with internal microchannels formed by cavitation at varying pH support future development in diverse applications including tissue engineering, drug delivery, and biomimetic lab-on-a-chip systems.