Lights, camera, vaporization: Coupling acoustics and microscopy to study acoustic droplet vaporization

Within the Department of Radiology at the University of Michigan, we have integrated mechanics, material science, and biomedical acoustics to develop ultrasound-assisted therapies and diagnostic techniques. What is our approach? Using ultrasound-responsive droplets. These droplets phase-transition from liquid to gas bubbles when exposed to ultrasound, a process termed acoustic droplet vaporization (ADV). We harness this transformation for a wide array of biomedical applications, such as delivering therapeutic payloads, modulating hydrogel properties, and characterizing material properties. In this video, we will demonstrate how to make monodisperse droplets using microfluidic techniques and prepare tissue-mimicking hydrogels containing these droplets for optical characterization. Resolving both the ADV-bubble response in an ultrasound field at clinically relevant frequencies, as well as the associated cellular and biological responses in real-time, requires high temporal and spatial resolution. To achieve this, we couple an ultra-high-speed camera (10 million frames per second) and time-lapse confocal fluorescence microcopy (1 frame per second). We will walk you through the process: aligning optical and ultrasound foci, coupling the transducer with samples on the microscope stage, aligning laser for high-intensity back illumination, synchronizing ultrasound and the camera, and finally, triggering ultrasound to generate ADV-bubbles