Open millifluidics based on powder-encased channels

In situ error analysis in contact angle goniometry

Contact angle goniometry is a valuable tool for characterising surface wetting properties in various application areas such as petrochemistry, coatings, and medicine. The accuracy of goniometer measurements is often unknown and underappreciated, yet the errors can be large enough to affect or invalidate the interpretation of measurement. In addition, goniometer measurement errors are typically estimated after the measurement by the variance of the measured data, without considering the instrumental uncertainties in the analysis or in the setup. Here, we present a method for estimating these intrinsic measurement errors for each frame in situ and validate it against a commercial contact angle goniometer. We evaluate the method using synthetic images of a droplet with set contact angles. Our results highlight the need for in situ error estimates in goniometer measurements, as the errors can be larger than generally estimated ones. The presented in situ error estimation method could be implemented using contact angle goniometer software to aid the user during the tuning of the instrument and analysis of the contact angle data.

Fluid Control on Bionics-Energized Surfaces

Engineered surfaces play a vital role in various fluid applications, serving specific functions such as self-cleaning, anti-icing, thermal management, and water energy harvesting. In nature, biological surfaces, particularly those displaying physiochemical heterogeneity, showcase remarkable fluid behaviors and functionalities, offering valuable insights for artificial designs. In this Review, we focus on exploring the fascinating fluid phenomena observed on natural biological surfaces and the manipulation of fluids on bioengineered surfaces, with a particular emphasis on droplets, liquid flows, and vapor flows. We delve into the fundamental principles governing symmetric fluid motion on homogeneous surfaces and directed fluid motion on heterogeneous surfaces. We discuss surface design strategies tailored to different fluid scenarios, outlining the strengths and limitations of engineered surfaces for specific applications. Additionally, the challenges faced by engineered surfaces in real-world fluid applications are put forward. By highlighting promising research directions, we hope to stimulate advancements in bioinspired engineering and fluid science, paving the way for future developments.

A Simple Route for Open Fluidic Devices with Particle Walls

Open fluidics, allowing liquid in a flow channel to interact with the external environment, is a revolutionary concept. However, fabricating a highly stable open fluidic device of arbitrary complexity, while maintaining reconfigurability, is still a challenge. This is achieved by the use of a patterned substrate and liquids that are covered with functional, readily available hydrophobic particles, providing great flexibility in the construction and use of open fluidic structures. Decorated with a coating of modified carbon nanotubes (CNTs) to encapsulate the fluids, the study capitalizes on the photothermal characteristics of CNTs to fabricate a device to probe the effects of temperature on tumor chemotherapy. The strategy substantially increases the availability and potential use of open fluidic devices.

Rod-Shaped Liquid Plasticine as Cuttable Minireactor for Photodynamic Therapy of Tumors

Photodynamic therapy (PDT) has emerged as a promising non-invasive approach for cancer treatment. Enhancing its efficacy and understanding its absorption-induced attenuation are significant while the solutions are limited, particularly for the latter. In this study, a rod-shaped liquid plasticine (LP), comprised of a tumor cell solution encased by a nanoparticle monolayer, is used to serve as a powerful minireactor for addressing these issues. The channel structure, openness, and cuttability of the LP reactor are exploited for providing benefits to PDT. The resulting PDT efficacy is several times higher than those from droplet reactors with common spherical shapes. The attenuation law, which is fundamental in PDT yet poorly understood due to the lack of experimental approaches, is preliminarily uncovered here from the perspective of in vitro experiments by using the LP's cuttability, affording quantitative understanding on this difficult subject. These findings provide insights into the widely-concerned topics in PDT, and highlight the great potential of an LP reactor in offering innovation power for the biochemical and biomedical arenas.

Quantitative Analysis of a Pilot Transwell Barrier Model with Automated Sampling and Mathematical Modeling

In the preclinical phase of drug development, it is necessary to determine how the active compound can pass through the biological barriers surrounding the target tissue. In vitro barrier models provide a reliable, low-cost, high-throughput solution for screening substances early in the drug candidate development process, thus reducing more complex and costly animal studies. In this pilot study, the transport properties of TB501, an antimycobacterial drug candidate, were characterized using an in vitro barrier model of VERO E6 kidney cells. The compound was delivered into the apical chamber of the transwell insert, and its concentration passing through the barrier layer was measured through the automated sampling of the basolateral compartment, where media were replaced every 30 min for 6 h, and the collected samples were stored for further spectroscopic analysis. The kinetics of TB501 concentration obtained from VERO E6 transwell cultures and transwell membranes saturated with serum proteins reveal the extent to which the cell layer functions as a diffusion barrier. The large number of samples collected allows us to fit a detailed mathematical model of the passive diffusive currents to the measured concentration profiles. This approach enables the determination of the diffusive permeability, the diffusivity of the compound in the cell layer, the affinity of the compound binding to the cell membrane as well as the rate by which the cells metabolize the compound. The proposed approach goes beyond the determination of the permeability coefficient and offers a more detailed pharmacokinetic characterization of the transwell barrier model. We expect the presented method to be fruitful in evaluating other compounds with different chemical features on simple in vitro barrier models. The proposed mathematical model can also be extended to include various forms of active transport.