Experimental Study on Acoustic Droplet Vaporization in a Microchannel

Acoustic droplet vaporization (ADV) in a microchannel, which is important in medical therapeutic applications such as embolization procedures for tumor treatment, was experimentally investigated using a high-speed camera and a microscope. The phase-change contrast agent (PCCA) consisted of a DDFP droplet with a boiling point of 29 °C, lower than the body temperature, and a phospholipid shell surrounding it. A PDMS microchannel with a cross section of 40μm by 50μm, which simulates a bio-microvessel, was fabricated by soft-lithography. Ultrasound with a center frequency of 5.25 MHz was applied to a phase-change microdroplet in the microchannel. The droplet is vaporized to a 5 times larger bubble, which fills the channel in the form of a vapor slug. Experiments for ADV in Y-channels are also conducted to investigate the dynamic behaviors of phase-change contrast agents. The effects of initial droplet size and channel configuration on the droplet and bubble motion were quantified.