Toward jet injection by continuous-wave laser cavitation

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

Continuous-wave laser generated jets for needle free applications

We designed and built a microfluidic device for the generation of liquid jets produced by thermocavitation. A continuous wave (CW) laser was focused inside a micro-chamber filled with a light-absorbing solution to create a rapidly expanding vapor bubble. The chamber is connected to a micro-channel which focuses and ejects the liquid jet through the exit. The bubble growth and the jet velocity were measured as a function of the devices geometry (channel diameter D and chamber width A). The fastest jets were those for relatively large chamber size with respect to the channel diameter. Elongated and focused jets up to 29 m/s for a channel diameter of 250 μm and chamber size of 700 μm were obtained. The proposed CW laser-based device is potentially a compact option for a practical and commercially feasible needle-free injecto

Efficient facemask decontamination via forced ozone convection

Abstract The COVID-19 crisis has taken a significant toll on human life and the global economy since its start in early 2020. Healthcare professionals have been particularly vulnerable because of the unprecedented shortage of Facepiece Respirators (FPRs), which act as fundamental tools to protect the medical staff treating the coronavirus patients. In addition, many FPRs are designed to be disposable single-use devices, creating an issue related to the generation of large quantities of non-biodegradable waste. In this contribution, we describe a plasma-based decontamination technique designed to circumvent the shortages of FPRs and alleviate the environmental problems posed by waste generation. The system utilizes a Dielectric Barrier Discharge (DBD) to generate ozone and feed it through the fibers of the FPRs. The flow-through configuration is different than canonical ozone-based sterilization methods, in which the equipment is placed in a sealed ozone-containing enclosure without any flow through the mask polymer fibers. We demonstrate the rapid decontamination of surgical masks using Escherichia coli (E. coli) and Vesicular Stomatitis Virus (VSV) as model pathogens, with the flow-through configuration providing a drastic reduction in sterilization time compared to the canonical approach. We also demonstrate that there is no deterioration in mask structure or filtration efficiency resulting from sterilization. Finally, we show that this decontamination approach can be implemented using readily available tools, such as a plastic box, a glass tube, few 3D printed components, and the high-voltage power supply from a plasma globe toy. The prototype assembled for this study is portable and affordable, with effectiveness comparable to that of larger and more expensive equipment

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Temporal evolution of liquid columns that emerge from a droplet of 5 µL volume at different x values from the center of the droplet´s base

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Formation and evolution of a liquid column formed by thermocavitation. The time interval between two images is 690 µs

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Formation and evolution of a vapor bubble created inside a droplet (5µL volume) using a CW laser. The laser focus was placed at the position (0,0,0)

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Temporal evolution of liquid columns that emerge from a droplet of 5 µL volume at different x values from the center of the droplet´s base

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Vapor bubble formed within a droplet of 5 µL of volume. The laser focus position was placed at z=0 and x=-400µm

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Temporal evolution of liquid columns that emerge from a droplet of 5 µL volume at different x values from the center of the droplet´s base