Reconfigurable microfluidic circuits for isolating and retrieving cells of interest

Microfluidic devices are widely used in many fields of biology, but a key limitation is that cells are typically surrounded by solid walls, making it hard to access those that exhibit a specific phenotype for further study. Here, we provide a general and flexible solution to this problem that exploits the remarkable properties of microfluidic circuits with fluid walls - transparent interfaces between culture media and an immiscible fluorocarbon that are easily pierced with pipets. We provide two proofs-of-concept in which specific cell sub-populations are isolated and recovered: i) murine macrophages chemotaxing towards complement component 5a, and ii) bacteria (Pseudomonas aeruginosa) in developing biofilms that migrate towards antibiotics. We build circuits in minutes on standard Petri dishes, add cells, pump in laminar streams so molecular diffusion creates attractant gradients, acquire time-lapse images, and isolate desired sub-populations in real-time by building fluid walls around migrating cells with an accuracy of tens of micrometres using 3D-printed adaptors that convert conventional microscopes into wall-building machines. Our method allows live cells of interest to be easily extracted from microfluidic devices for downstream analyses.

Topographically Controlled Marangoni-Rayleigh-Bénard Convection in Liquid Metals

Convection induced in a layer of liquid with a top free surface by a distribution of heating elements at the bottom can be seen as a variant of standard Marangoni–Rayleigh–Bénard Convection where in place of a flat boundary at constant temperature delimiting the system from below, the underlying thermal inhomogeneity reflects the existence of a topography. In the present work, this problem is investigated numerically through solution of the governing equations for mass, momentum and energy in their complete, three-dimensional time-dependent and non-linear form. Emphasis is given to a class of liquids for which thermal diffusion is expected to dominate over viscous effects (liquid metals). Fixing the Rayleigh and Marangoni number to 104 and 5 × 103, respectively, the sensitivity of the problem to the geometrical, kinematic and thermal boundary conditions is investigated parametrically by changing: the number and spacing of heating elements, their vertical extension, the nature of the lateral boundary (solid walls or periodic boundary) and the thermal behavior of the portions of bottom wall between adjoining elements (assumed to be either adiabatic or at the same temperature of the hot blocks). It is shown that, like the parent phenomena, this type of thermal flow is extremely sensitive to the specific conditions considered. The topography can be used to exert a control on the emerging flow in terms of temporal response and patterning behavior.

Predicting flows through microfluidic circuits with fluid walls

The aqueous phase in traditional microfluidics is usually confined by solid walls; flows through such systems are often predicted accurately. As solid walls limit access, open systems are being developed in which the aqueous phase is partly bounded by fluid walls (interfaces with air or immiscible liquids). Such fluid walls morph during flow due to pressure gradients, so predicting flow fields remains challenging. We recently developed a version of open microfluidics suitable for live-cell biology in which the aqueous phase is confined by an interface with an immiscible and bioinert fluorocarbon (FC40). Here, we find that common medium additives (fetal bovine serum, serum replacement) induce elastic no-slip boundaries at this interface and develop a semi-analytical model to predict flow fields. We experimentally validate the model’s accuracy for single conduits and fractal vascular trees and demonstrate how flow fields and shear stresses can be controlled to suit individual applications in cell biology.

The Visual, Auditory, and Physical Environment of Livestock Handling Facilities and Its Effect on Ease of Movement of Cattle, Pigs, and Sheep

The visual, auditory, and physical environment livestock are handled in will have an effect on the ease of movement through races and corrals that are used for veterinary treatment, loading trucks or at slaughter houses. When livestock refuse to move easily through a handling facility, people are more likely to use electric goads (prods) or other aversive methods to move them forward. This is a major animal welfare concern. Modification of the environment can improve livestock movement and reduce aversive handling methods. In existing facilities used for handling cattle, pigs or sheep, simple changes such as, adding a light to a dark race entrance or reducing loud intermittent noise may improve livestock movement. Eliminating distractions such as, a noisy truck near a lairage can also facilitate cattle movement and reduce stopping or turning back. In an outdoor facility, sharp shadows on the floor were more likely to be associated with cattle stopping compared to no shadows or soft faint shadows. The installation of small solid walls to prevent approaching animals from seeing either moving equipment, vehicles or people in front of them may also improve forward livestock movement. Non-slip flooring is essential to prevent slipping and falling during handling. Rebuilding or completely redesigning an existing facility is often not required. Outcome based indicators should be used to assess continuous improvements in handling. Some of the commonly used measurable of handling are slipping and falling, stopping, turning back, vocalization during handling and electric prod use. Collecting data both before and after an environmental modification can be used to determine its effectiveness.

Determination of Boussinesq and Coriolis coefficients for pipelines operating with discharge connection along the path

Peculiarities of the diagrams of averaged fluid velocities in the cross-sections of pressure collecting perforated pipelines were determined on the basis of the experimental studies conducted by the authors. The most characteristic typical diagrams of averaged velocities in the pipelines cross-sections with their different design characteristics were given. A comparative analysis of the obtained diagrams with the diagrams of velocities that occur during uniform motion in pressure pipelines with solid walls was carried out. It is shown that the main difference between them occurs in the flow zones, which are located near the pipeline walls. It was explained by the connected liquid jets effect on the main flow. The degree of diagrams deformation was estimated by the value of the momentum coefficient α0 (Boussinesq coefficient) and the coefficient of kinetic energy α (Coriolis coefficient). It was determined that in the general case these coefficients will be variable in magnitude along the length of the studied pipes. Nevertheless, these coefficients are recommended to be constant in magnitude in engineering calculations. The limits of the structural characteristics of collecting perforated pipes for which this non-uniformity of the diagrams must be taken into account, and for which it can be neglected were determined on the basis of the analysis of the equation of fluid motion with a variable flow rate.

Material Dissolve: A Poetics Of Spatial Encounters

We are increasingly alienated from the direct sensual and intellectual encounter of space, in an epoch that gradually supplements direct spatial experience with mediated digital experience. This research reprises aspects of Phenomenology. In opposition to Phenomenology’s proponents like Zumthor—that seek to reassert the bodily presence of architecture through a kind of hypermateriality that asserts a material intensity, this thesis investigates a methodology to re-engage humans with physical spatial experience through the de-materialization of the wall. Distinct from the history of Modernist explorations of absolute transparency, and material lightness, this investigation is more akin to what Kengo Kuma calls “ Thesis Statement A spatial poetic can be created through the fusion of light and time with matter. The architectural experience is one where bodies are sensorially and intellectually engaged in moving through a series of articulated spaces. The orchestration of this movement between a series of semi-solid “walls” creates an environment of heightened sensory awareness where boundaries blur between constantly oscillating states of opacity and transparency created by the path of the user. Through literary research, precedent analysis, and a design project that explores and tests these ideas, this thesis asserts the creation of a poetics of space through this new approach to material presence, and its experience as part of a narrative sequence of encounter.

Material Dissolve: A Poetics Of Spatial Encounters

We are increasingly alienated from the direct sensual and intellectual encounter of space, in an epoch that gradually supplements direct spatial experience with mediated digital experience. This research reprises aspects of Phenomenology. In opposition to Phenomenology’s proponents like Zumthor—that seek to reassert the bodily presence of architecture through a kind of hypermateriality that asserts a material intensity, this thesis investigates a methodology to re-engage humans with physical spatial experience through the de-materialization of the wall. Distinct from the history of Modernist explorations of absolute transparency, and material lightness, this investigation is more akin to what Kengo Kuma calls “ Thesis Statement A spatial poetic can be created through the fusion of light and time with matter. The architectural experience is one where bodies are sensorially and intellectually engaged in moving through a series of articulated spaces. The orchestration of this movement between a series of semi-solid “walls” creates an environment of heightened sensory awareness where boundaries blur between constantly oscillating states of opacity and transparency created by the path of the user. Through literary research, precedent analysis, and a design project that explores and tests these ideas, this thesis asserts the creation of a poetics of space through this new approach to material presence, and its experience as part of a narrative sequence of encounter.