Microfluidics control the ballistic energy of thermocavitation liquid jets for needle-free injections

Abstract

Illuminating a water solution with a focused continuous wave laser produces a strong local heating of the liquid that leads to the nucleation of bubbles, also known as thermocavitation. During the growth of the bubble, the surrounding liquid is expelled from the constraining microfluidic channel through a nozzle, creating a jet. The characteristics of the resulting liquid jet was imaged using ultra-fast imaging techniques. Here, we provide a phenomenological description of the jet shapes and velocities, and compare them with a Boundary Integral numerical model. We define the parameter regime, varying jet speed, taper geometry and liquid volume, for optimal printing, injection and spray applications. These results are important for the design of energy-efficient needle-free jet injectors based on microfluidic thermocavitation. arXiv:2003.00934v1 [physics.flu-dyn]

Impact of a microfluidic jet on a pendant droplet

“…The red dye enhances the laser energy absorption and facilitates bubble nucleation. The microfluidic device has a tapered channel with an angle α = 15 degrees to avoid swirling of the jet, 17 nozzle diameter d = 120 μm, channel length L = 1050 μm and width W = 600 μm. The thermocavitation bubble is created by focusing a continuous wave laser diode (Roithner LaserTechnik, wavelength Λ = 450 nm and nominal power of 3.5 W), on the microchannel using a 10× microscope objective.…”

Dynamics of pulsed laser-induced cavities on a liquid–gas interface: from a conical splash to a ‘bullet’ jet

“…It is worth mentioning that the impact speeds observed during these trials should be high enough to produce the piercing of a soft material or biological tissue, as discussed in Cu et al (2020), Oyarte Gálvez et al (2020 and Robles et al (2020).…”

“…Jet impact on a solid surface and potential applications As discussed in the previous sections, the bullet jet's evolution is mostly defined by the 'local' dynamics of the splash, instead of the boundary conditions outside of the region where the laser cavitation takes place (for instance a neighbouring solid wall). This, combined with the particularly long distances that the jet can reach (∼12 times R cm ) and the total length of the liquid stream (∼3 times R cm ), make bullet jets potentially useful for certain applications, specifically, applications dealing with the cleaning of millimetric surfaces (Ohl et al 2006), membrane poration (Gonzalez-Avila et al 2020) or even micro-vaccination or drug delivery platforms (Cu et al 2020;Oyarte Gálvez et al 2020;Robles et al 2020). The bullet jet could be particularly useful in systems with limited access, for example one which can only be accessed by optical means.…”

“…Some unique aspects are: the relatively long distances that the liquid stream can reach, and also the amount of fluid transported in the liquid jet. Furthermore, this kind of jet could be of use in diverse applications such as bubble cleaning (Ohl et al 2006), or a drug delivery system that automatically directs the drug to a specific location repeatably, such as micro-vaccination or drug delivery platforms (Cu et al 2020;Oyarte Gálvez et al 2020;Robles et al 2020).…”

Cavity collapse near slot geometries

“…Developing a better understanding of the effects of cavitation collapse can increase the lifespan of components such as ship propellers (van Terwisga et al 2007) and tidal turbines (Kumar & Saini 2010) or determine the effectiveness of ultrasonic cleaning for complex geometries (Verhaagen, Zanderink & Fernández Rivas 2016; Reuter et al 2017). There are also numerous applications in biomedical fields such as reducing tissue damage during surgery (Palanker, Vankov & Miller 2002), investigating mechanisms of cell death in cases where cavitation could be used for drug delivery (Dijkink et al 2008), using cavitation to facilitate needle-free injections (Oyarte Gálvez et al 2020) and studying the contribution of cavitation in traumatic brain injuries (Canchi et al 2017) where cavitation is induced by high accelerations (Pan et al 2017). More novel applications of cavitation include producing high-speed liquid jets at small scales (Karri et al 2012), using cavitation as an ice-breaking mechanism (Cui et al 2018) and understanding biological mechanisms such as those employed by the snapping shrimp (Versluis et al 2000; Shimu et al 2019).…”