Pharmaceutical-grade oral films as substrates for printed medicine

In contact-less printing, such as piezo-electric drop on demand printing used in the study, the drop formation process is independent of the substrate. This means that having developed a printable formulation, printed pharmaceutical dosage forms can be obtained on any pharmaceutical grade substrate, such as polymer-based films. In this work we evaluated eight different oral films based on their suitability as printing substrates for sodium picosulfate. The different polymer films were compared regarding printed spot morphology, chemical stability and dissolution profile. The morphology of printed sodium picosulfate was investigated with scanning electron microscopy and optical coherence tomography. The spreading of the deposited drops was found to be governed by the contact angle of the ink with the substrate. The form of the sodium picosulfate drops changed on microcrystalline cellulose films at ambient conditions over 8 weeks and stayed unchanged on other tested substrates. Sodium picosulfate remained amorphous on all substrates according to small and wide angle X-ray scattering, differential scanning calorimetry and polarized light microscopy measurements. The absence of chemical interactions between the drug and substrates, as indicated by infrared spectroscopy, makes all tested substrates suitable for printing sodium picosulfate onto them

Mapping outcomes of liquid marble collisions

© 2019 The Royal Society of Chemistry. Liquid marbles (LMs) have many promising roles in the ongoing development of microfluidics, microreactors, bioreactors, and unconventional computing. In many of these applications, the coalescence of two LMs is either required or actively discouraged, therefore it is important to study liquid marble collisions and establish parameters which enable the desired collision outcome. Recent reports on LM coalescence have focused on either two mobile LMs colliding, or an accelerating LM hitting a sessile LM with a backstop. A further possible scenario is the impact of a mobile LM against a non-supported static LM. This paper investigates such a collision, using high-speed videography for single-frame analysis. Multiple collisions were undertaken whilst varying the modified Weber number (We∗) and offset ratios (X∗). Parameter ranges of 1.0 0.25, and We∗ 1.55 resulted in 100% non-coalescence. Additionally, observations of LMs moving above a threshold velocity of 0.6 m s -1 have revealed a new and unusual deformation. Comparisons of the outcome of collisions whilst varying both the LM volume and the powder grain size have also been made, revealing a strong link. The results of this work provide a deeper understanding of LM coalescence, allowing improved control when designing future collision experiments

Liquid encapsulation by binary collisions of immiscible liquid drops

International audienceIn this paper, we present binary collisions of immiscible liquid drops as a promising and reliable process for encapsulating liquids in shells of other, immiscible liquids. Our current experimental approach describes the collision outcome according to relevant parameters. Depending on the drop size and the relative velocity, the impact parameter and liquid viscosity, density and surface tension, we observe that either the full drop of encapsulating liquid spreads around the encapsulated one, or part of it separates, while the rest remains attached. We show that the viscosities of the two liquids do not have equal importance for the stability limit of the process, especially for head-on collisions. For separation after the collision, a new mechanism is identified which does not occur with miscible liquid drop collisions. For separated drops, the thickness of the remaining liquid shell was also investigated and turns out to be independent of both liquid viscosities and relative velocity. As a consequence, we can accurately adjust the thickness of the coating layer by simply tuning the impact parameter of the collision.Aninterpretation of this behavior based on a geometric argument is proposed

Transition of liquid marble impacts onto solid surfaces

International audienceLiquid marbles are liquid droplets covered with hydrophobic particles. This particular layer physically isolates them from the substrate on which they are deposited. In this study, we investigate the properties of such liquid marbles when impacting onto a solid substrate. The different behaviors during impact (non-bouncing, bouncing and rupture) are experimentally characterized and scenarios for understanding the transitions between the three regimes are proposed. Eventually, we highlight the importance of particle surface coverage by comparing the impact of a liquid marble on a smooth surface with the impact of a bare water drop on a rough superhydrophobic microtextured surface. Copyright (C) EPLA, 201

Coalescence of armored interface under impact

International audienceArmored interfaces refer to fluid interfaces on which a compact monolayer of particles is adsorbed. In this paper, we probe their robustness under impact. For such an investigation, the impact of a drop (covered or not by particles) on a flat armored interface is considered. Two regimes are observed: small drops impacting at low velocities do not coalesce, while bigger drops falling at higher velocities lead to coalescence. The coalescence which occurs when the impacting drop has just reached its maximum extension directly results from the formation of bare regions within the armor. We therefore propose a geometric criterion to describe this transition. This simple modeling is able to capture the dependence of the measured velocity threshold with particle size and drop diameter. The additional robustness experienced by double armors (both drop and puddle covered) results in an increase of the measured velocity threshold, which is quantitatively predicted. © 2013 AIP Publishing LLC