Toward jet injection by continuous-wave laser cavitation

Abstract

This is a study motivated by the need to develop a needle-free device for eliminating major global healthcare problems caused by needles. The generation of liquid jets by means of a continuous-wave laser, focused into a light absorbing solution, was studied with the aim of developing a portable and affordable jet injector. We designed and fabricated glass microfluidic devices, which consist of a chamber where thermocavitation is created and a tapered channel. The growth of a vapor bubble displaces and expels the liquid through the channel as a fast traveling jet. Different parameters were varied with the purpose of increasing the jet velocity. The velocity increases with smaller channel diameters and taper ratios, whereas larger chambers significantly reduce the jet speed. It was found that the initial position of the liquid-air meniscus interface and its dynamics contribute to increased jet velocities. A maximum velocity of 94±3 m/s for a channel diameter of D=120 μm, taper ratio n=0.25, and chamber length E=200 μm was achieved. Finally, agarose gel-based skin phantoms were used to demonstrate the potential of our devices to penetrate the skin. The maximum penetration depth achieved was ∼1 mm, which is sufficient to penetrate the stratum corneum and for most medical applications. A meta-analysis shows that larger injection volumes will be required as a next step to medical relevance for laser-induced jet injection techniques in general.

Repetitive regime of highly focused liquid microjets for needle-free injection

“…Jets were mostly stopped by the reticular dermis and reached the hypodermis with the efficiency of only 12%. With regard to the diagram presented by Rodríguez et al 18 we can claim, that such shallow penetration prevents this technology from delivering a drug aimed to reach the hypodermis or muscle tissue.…”

A Comparison of Drug Delivery into Skin Using Topical Solutions, Needle Injections and Jet Injections

“…The fabrication process and design of these devices were previously described elsewhere. 8,9 The microfluidic devices consisted of two rectangular channels with 100 μm depth:…”

“…16,17 From the different energy sources used to power NFIs, a recent example is based on continuous wave (CW) lasers that cause a phenomenon known as thermocavitation to create liquid jets by heating the injectate above its boiling point with an explosive phase transition. 8,9,27,28,35 This work evaluates a CW-based needle-free micro-jet injector as a possible transdermal delivery alternative with minimal damage to the skin structure. For the purpose of this study, the topical solution delivery will be primarily associated with diffusion processes.…”

Thermocavitation in a Microchannel with a Low Power Light Source

“…Cavitation induced by lasers has been ultimately used for development of technolgies, such as needle free injection [1,2,3] and ink-jet printing [4,5]. Pulsed-laser-based systems produce very fast jets, however they are expensive, noisy, heavy, among others [1,6,7].…”

“…Cavitation induced by lasers has been ultimately used for development of technolgies, such as needle free injection [1,2,3] and ink-jet printing [4,5]. Pulsed-laser-based systems produce very fast jets, however they are expensive, noisy, heavy, among others [1,6,7]. Recently, it has been demonstrated that continuous wave lasers -which are cheaper, lighter, more portable and with lower safety risks than pulsed lasers-are able to induce jets by cavitation with speeds up to ∼100m/s [1,8], becoming a more efficient alternative for the mentioned technologies.…”