Electro-actuated valves and self-vented channels enable programmable flow control and monitoring in capillary-driven microfluidics.
Ontology highlight
ABSTRACT:
SUBMITTER: Arango Y
PROVIDER: S-EPMC7250678 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:Small volume fluid handling in single and multiphase microfluidics provides a promising strategy for efficient bio-chemical assays, low-cost point-of-care diagnostics and new approaches to scientific discoveries. However multiple barriers exist towards low-cost field deployment of programmable microfluidics. Incorporating multiple pumps, mixers and discrete valve based control of nanoliter fluids and droplets in an integrated, programmable manner without additional required external components has remained elusive. Combining the idea of punch card programming with arbitrary fluid control, here we describe a self-contained, hand-crank powered, multiplex and robust programmable microfluidic platform. A paper tape encodes information as a series of punched holes. A mechanical reader/actuator reads these paper tapes and correspondingly executes operations onto a microfluidic chip coupled to the platform in a plug-and-play fashion. Enabled by the complexity of codes that can be represented by a series of holes in punched paper tapes, we demonstrate independent control of 15 on-chip pumps with enhanced mixing, normally-closed valves and a novel on-demand impact-based droplet generator. We demonstrate robustness of operation by encoding a string of characters representing the word "PUNCHCARD MICROFLUIDICS" using the droplet generator. Multiplexing is demonstrated by implementing an example colorimetric water quality assays for pH, ammonia, nitrite and nitrate content in different water samples. With its portable and robust design, low cost and ease-of-use, we envision punch card programmable microfluidics will bring complex control of microfluidic chips into field-based applications in low-resource settings and in the hands of children around the world.
| S-EPMC4349784 | biostudies-literature
Project description:The differential migration of ions in an applied electric field is the basis for separation of chemical species by capillary electrophoresis. Axial diffusion of the concentration peak limits the separation efficiency. Electromigration dispersion is observed when the concentration of sample ions is comparable to that of the background ions. Under such conditions, the local electrical conductivity is significantly altered in the sample zone making the electric field, and therefore, the ion migration velocity concentration dependent. The resulting nonlinear wave exhibits shock like features, and, under certain simplifying assumptions, is described by Burgers' equation (S. Ghosal and Z. Chen Bull. Math. Biol. 201072, pg. 2047). In this paper, we consider the more general situation where the walls of the separation channel may have a non-zero zeta potential and are therefore able to sustain an electro-osmotic bulk flow. The main result is a one dimensional nonlinear advection diffusion equation for the area averaged concentration. This homogenized equation accounts for the Taylor-Aris dispersion resulting from the variation in the electro-osmotic slip velocity along the wall. It is shown that in a certain range of parameters, the electro-osmotic flow can actually reduce the total dispersion by delaying the formation of a concentration shock. However, if the electro-osmotic flow is sufficiently high, the total dispersion is increased because of the Taylor-Aris contribution.
| S-EPMC3563067 | biostudies-literature
Project description:Characterizing the thermal behavior of dispersed droplets within microfluidic channels is crucial for different applications in lab-on-a-chip. In this paper, the physics of droplets volume during their transport over a heater is studied experimentally and numerically. The response of droplets to external heating is examined at temperature ranges of 25-90 °C and at different flow rates of the dispersed phase respect to the continuous flow. The results present a reliable prediction of the droplet volume and stability when heating is applied to the droplets at the downstream channel in a quite far distance from the droplets' ejection orifice. Increasing the ratio of flow rate resulted in larger droplets; for instance, the flow ratio of 0.25 produced drops with 40% larger diameter than the flow rate of 0.1. For every 10 °C increase in temperature of the droplets, the droplet diameter increased by about 5.7% and 4.2% for pure oil and oil with a surfactant, respectively. Also, the droplets showed a degree of instability during their transport over the heater at higher temperatures. Adding SPAN 20 surfactant improved the stability of the droplets at temperatures higher than 60 °C. The experimentally validated numerical model helped for systemic analysis of the influence of key temperature-dependence parameters (e.g. surface tension, density and viscosity of both phases) on controlling the volume and stability of droplets. Our findings supported to develop highly functional systems with a predetermined droplets performance under high temperatures up to 90 °C. This report provides a preliminary basis for enhancing the performance of droplet microfluidic systems for digital droplet polymerase chain reaction (ddPCR), continuous flow digital loop-mediated isothermal PCR (LAMP), and droplet-based antibiotic susceptibility testing.
| S-EPMC6405956 | biostudies-literature
Project description:Droplet manipulations are fundamental to numerous applications, such as water collection, medical diagnostics, and drug delivery. Structure-based liquid operations have been widely used both in nature and in artificial materials. However, current strategies depend mainly on fixed structures to realize unidirectional water movement, while multiple manipulation of droplets is still challenging. Here, we propose a magnetic-actuated robot with adjustable structures to achieve programmable multiple manipulations of droplets. The adjustable structure redistributes the resisting forces from the front and rear ends of the droplets, which determine the droplet behaviors. We can transport, split, release, and rotate the droplets using the robot. This robot is universally applicable for manipulation of various fluids in rough environments. These findings offer an efficient strategy for automated manipulation of droplets.
| S-EPMC7021501 | biostudies-literature
Project description:The artificial ciliary motion has been known not to be hydrodynamically optimal, limiting their associated applications in the microscale flow domain. One of the major hurdles of contemporary artificial cilia is its structural rigidity, which restricts their flexibility. To address this issue, this work proposed a shape-programmable artificial cilia design with distinctive polydimethylsiloxane (PDMS) and magnetic segments distributed throughout the structure, which provided precise control for time-spatial modulation of the whole artificial cilia structure under external magnetic actuation. For the fabrication of the proposed multi-segment artificial cilia, a facile microfabrication process with stepwise mold blocking followed by the PDMS and magnetic composite casting was adopted. The hydrodynamic analysis further elucidated that the proposed artificial cilia beating induced significant flow disturbance within the flow field, and the associated application was demonstrated through an efficient mixing operation.
| S-EPMC8605101 | biostudies-literature
Project description:Capillary electrochromatography (CEC) is a micro-scale separation technique which is a hybrid between capillary electrophoresis (CE) and liquid chromatography (LC). CEC can be performed in packed, monolithic and open-tubular columns. In recent three years (from 2016 to 2018), enormous attention for CEC has been the development of novel stationary phases. This review mainly covers the development of novel stationary phases for open-tubular and monolithic columns. In particular, some biomaterials attracted increasing interest. There are no significant breakthroughs in technology and principles in CEC. The typical CEC applications, especially chiral separations are described.
| S-EPMC6702421 | biostudies-literature
Project description:The programmable CSF shunt valve has become an important tool in hydrocephalus treatment, particularly in the NPH population and in pediatric patients with complex hydrocephalus. The purpose of this study is to provide a single reference for the identification of programmable shunt valves and the interpretation of programmable shunt valve settings. Four major manufacturers of programmable shunts agreed to participate in this study. Each provided radiographic images and legends for their appropriate interpretation. Issues of MR imaging compatibility for each valve are also discussed.
| S-EPMC7965480 | biostudies-literature
Project description:An inexpensive, disposable, integrated, polymer-based cassette for loop-mediated isothermal amplification (LAMP) of target nucleic acids was designed, fabricated, and tested. The LAMP chamber was equipped with single-use, thermally actuated valves made with a composite consisting of a mixture of PDMS and expandable microspheres. The effect of the composite composition on its expansion was investigated, and the valve's performance was evaluated. In its closed state, the valve can hold pressures as high as 200 kPa without any significant leakage. Both the LAMP chamber and the valves were actuated with thin film heaters. The utility of the cassette was demonstrated by carrying out LAMP of Escherichia coli DNA target and reverse transcribed loop meditated isothermal amplification (RT-LAMP) of RNA targets. The amplicons were detected in real time with a portable, compact detector. The system was capable of detecting as few as 10 target molecules per sample in well under 1 h. The portable, integrated cassette system described here is particularly suited for applications at the point of care and in resource-poor countries, where funds and trained personnel are in short supply.
| S-EPMC7088409 | biostudies-literature
Project description:We propose a new class of magnetically actuated pumps and valves that could be incorporated into microfluidic chips with no further external connections. The idea is to repurpose ferromagnetic low Reynolds number swimmers as devices capable of generating fluid flow, by restricting the swimmers' translational degrees of freedom. We experimentally investigate the flow structure generated by a pinned swimmer in different scenarios, such as unrestricted flow around it as well as flow generated in straight, cross-shaped, Y-shaped and circular channels. This demonstrates the feasibility of incorporating the device into a channel and its capability of acting as a pump, valve and flow splitter. Different regimes could be selected by tuning the frequency and amplitude of the external magnetic field driving the swimmer, or by changing the channel orientation with respect to the field. This versatility endows the device with varied functionality which, together with the robust remote control and reproducibility, makes it a promising candidate for several applications.
| S-EPMC5772482 | biostudies-literature
Project description:Cell culture systems are often static and are therefore nonphysiological. In vivo, many cells are exposed to dynamic surroundings that stimulate cellular responses in a process known as mechanotransduction. To recreate this environment, stretchable cell culture substrate systems have been developed, however, these systems are limited by being macroscopic and low throughput. We have developed a device consisting of 24 miniature cell stretching chambers with flexible bottom membranes that are deformed using the computer-controlled, piezoelectrically actuated pins of a Braille display. We have also developed efficient image capture and analysis protocols to quantify morphological responses of the cells to applied strain. Human dermal microvascular endothelial cells (HDMECs) were found to show increasing degrees of alignment and elongation perpendicular to the radial strain in response to cyclic stretch at increasing frequencies of 0.2, 1, and 5 Hz, after 2, 4, and 12h. Mouse myogenic C2C12 cells were also found to align in response to the stretch, while A549 human lung adenocarcinoma epithelial cells did not respond to stretch.
| S-EPMC2386516 | biostudies-literature