Microfluidic jet impacts on deep pools transition from capillary-dominated cavity closure to gas pressure-dominated closure at higher Weber numbers.

Studying liquid jet impacts on a liquid pool is crucial for various engineering and environmental applications. During jet impact, the free surface of the pool deforms and a cavity is generated. Simultaneously, the free surface of the cavity extends radially outward and forms a rim.

Ultrasound and sonochemistry enhance education outcomes: From fundamentals and applied research to entrepreneurial potential.

With this manuscript we aim to initiate a discussion specific to educational actions around ultrasonics sonochemistry. The importance of these actions does not just derive from a mere pedagogical significance, but they can be an exceptional tool for illustrating various concepts in other disciplines, such as process intensification and microfluidics. Sonochemistry is currently a far-reaching discipline extending across different scales of applicability, from the fundamental physics of tiny bubbles and molecules, up to process plants.

Microfluidic jet impact: Spreading, splashing, soft substrate deformation and injection.

Hypothesis: Needle-free injections using microfluidic jets could be optimized by reducing splashing and controlling injection depth. However, this is impeded by an incomplete understanding on how jet characteristics influence impact outcome. We hypothesise that exploring the relation between microfluidic jet characteristics and substrate shear modulus on impact behavior will assist in predicting and giving insights on the impact outcome on skin and injection endpoints.

Cavity dynamics after the injection of a microfluidic jet onto capillary bridges.

The ballistics of solid and liquid objects (projectiles) impacting on liquids and soft solids (targets) generally results in the creation and expansion of an air cavity inside the impacted object. The dynamics of cavity expansion and collapse depends on the projectile inertia as well as on the target properties. In this paper we study the impact of microfluidic jets generated by thermocavitation processes on a capillary bridge between two parallel planar walls.

Jet injectors: Perspectives for small volume delivery with lasers.

Needle-free jet injectors have been proposed as an alternative to injections with hypodermic needles. Currently, a handful of commercial needle-free jet injectors already exist. However, these injectors are designed for specific injections, typically limited to large injection volumes into the deeper layers beneath the skin.

Mitigating losses: how scientific organisations can help address the impact of the COVID-19 pandemic on early-career researchers.

Scientific collaborations among nations to address common problems and to build international partnerships as part of science diplomacy is a well-established notion. The international flow of people and ideas has played an important role in the advancement of the 'Sciences' and the current pandemic scenario has drawn attention towards the genuine need for a stronger role of science diplomacy, science advice and science communication. In dealing with the COVID-19 pandemic, visible interactions across science, policy, science communication to the public and diplomacy worldwide have promptly emerged.

Correction: Mitigating losses: how scientific organisations can help address the impact of the COVID-19 pandemic on early-career researchers.

[This corrects the article DOI: 10.1057/s41599-021-00944-1.].

Impact of a microfluidic jet on a pendant droplet.

High speed microfluidic jets can be generated by a thermocavitation process: from the evaporation of the liquid inside a microfluidic channel, a rapidly expanding bubble is formed and generates a jet through a flow focusing effect. Here, we study the impact and traversing of such jets on a pendant liquid droplet. Upon impact, an expanding cavity is created, and, above a critical impact velocity, the jet traverses the entire droplet.

Assessment of cytotoxicity and sensitization potential of intradermally injected tattoo inks in reconstructed human skin.

Background: The number of people within the European population having at least one tattoo has increased notably, and with it the number of tattoo-associated clinical complications. Despite this, safety information and testing regarding tattoo inks remain limited.

Objective: To assess cytotoxicity and sensitization potential of 16 tattoo inks after intradermal injection into reconstructed human skin (RHS).

Challenges and opportunities for small volumes delivery into the skin.

Each individual's skin has its own features, such as strength, elasticity, or permeability to drugs, which limits the effectiveness of one-size-fits-all approaches typically found in medical treatments. Therefore, understanding the transport mechanisms of substances across the skin is instrumental for the development of novel minimal invasive transdermal therapies. However, the large difference between transport timescales and length scales of disparate molecules needed for medical therapies makes it difficult to address fundamental questions.

Cavitation intensifying bags improve ultrasonic advanced oxidation with Pd/AlO catalyst.

Advanced oxidation processes can potentially eliminate organic contaminants from industrial waste streams as well as persistent pharmaceutical components in drinking water. We explore for the first time the utilization of Cavitation Intensifying Bags (CIB) in combination with Pd/AlO catalyst as possible advanced oxidation technology for wastewater streams, oxidizing terephthalic acid (TA) to 2-hydroxyterephthalic acid (HTA). The detailed characterization of this novel reaction system reveals that, during sonication, the presence of surface pits of the CIB improves the reproducibility and thus the control of the sonication process, when compared to oxidation in non-pitted bags.

Delivery Strategies for Skin: Comparison of Nanoliter Jets, Needles and Topical Solutions.

Drug diffusion within the skin with a needle-free micro-jet injection (NFI) device was compared with two well-established delivery methods: topical application and solid needle injection. A permanent make-up (PMU) machine, normally used for dermal pigmentation, was utilized as a solid needle injection method. For NFIs a continuous wave (CW) laser diode was used to create a bubble inside a microfluidic device containing a light absorbing solution.

Acoustophoretic focusing effects on particle synthesis and clogging in microreactors.

The handling of solids in microreactors represents a challenging task. In this paper, we present an acoustophoretic microreactor developed to manage particles in flow and to control the material synthesis process. The reactor was designed as a layered resonator with an actuation frequency of 1.

Electrolysis-Driven and Pressure-Controlled Diffusive Growth of Successive Bubbles on Microstructured Surfaces.

Control over the bubble growth rates forming on the electrodes of water-splitting cells or chemical reactors is critical with respect to the attainment of higher energy efficiencies within these devices. This study focuses on the diffusion-driven growth dynamics of a succession of H bubbles generated at a flat silicon electrode substrate. Controlled nucleation is achieved by means of a single nucleation site consisting of a hydrophobic micropit etched within a micrometer-sized pillar.

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.

Is reproducibility inside the bag? Special issue fundamentals and applications of sonochemistry ESS-15.

In this paper we report our most recent attempts to tackle a notorious problem across several scientific activities from the ultrasonics sonochemical perspective: reproducibility of results. We provide experimental results carried out in three different laboratories, using the same ingredients: ultrasound and a novel cavitation reactor bag. The main difference between the experiments is that they are aimed at different applications, KI liberation and MB degradation; and exfoliation of two nanomaterials: graphene and molybdenum disulfide.

Emulsification in novel ultrasonic cavitation intensifying bag reactors.

Cavitation Intensifying Bags (CIBs), a novel reactor type for use with ultrasound, have been recently proposed as a scaled-up microreactor with increased energy efficiencies. We now report on the use of the CIBs for the preparation of emulsions out of hexadecane and an SDS aqueous solution. The CIBs have been designed in such a way that cavitation effects created by the ultrasound are increased.

Synergy of Microfluidics and Ultrasound : Process Intensification Challenges and Opportunities.

A compact snapshot of the current convergence of novel developments relevant to chemical engineering is given. Process intensification concepts are analysed through the lens of microfluidics and sonochemistry. Economical drivers and their influence on scientific activities are mentioned, including innovation opportunities towards deployment into society.

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.

Measuring cavitation and its cleaning effect.

The advantages and limitations of techniques for measuring the presence and amount of cavitation, and for quantifying the removal of contaminants, are provided. After reviewing chemical, physical, and biological studies, a universal cause for the cleaning effects of bubbles cannot yet be concluded. An "ideal sensor" with high spatial and temporal resolution is proposed.

Enhancing acoustic cavitation using artificial crevice bubbles.

We study the response of pre-defined cavitation nuclei driven continuously in the kHz regime (80, 100 and 200 kHz). The nuclei consist of stabilized gaspockets in cylindrical pits of 30 μm diameter etched in silicon or glass substrates. It is found that above an acoustic pressure threshold the dynamics of the liquid-gas meniscus switches from a stable drum-like vibration to expansion and deformation, frequently resulting in detachment of microbubbles.

Cavitation measurement during sonic and ultrasonic activated irrigation.

Introduction: The aims of this study were to quantify and to visualize the possible occurrence of transient cavitation (bubble formation and implosion) during sonic and ultrasonic (UAI) activated irrigation.

Methods: The amount of cavitation generated around several endodontic instruments was measured by sonochemiluminescence dosimetry inside 4 root canal models of human dimensions and varying complexity. Furthermore, the spatial distribution of the sonochemiluminescence in the root canal was visualized with long-exposure photography.