Method for Characterization of Passive Mechanical Filtration of Particles in Digital Microfluidic Devices

Author(s):  
Peter D. Dunning ◽  
Pierre E. Sullivan ◽  
Michael J. Schertzer

The ability to remove unbound biological material from a reaction site has applications in many biological protocols, such as those used to detect pathogens and biomarkers. One specific application where washing is critical is the Enzyme-Linked ImmunoSorbent Assay (ELISA). This protocol requires multiple washing steps to remove multiple reagents from a reaction site. Previous work has suggested that a passive mechanical comb filter can be used to wash particles in digital microfluidic devices. A method for the characterization of passive mechanical filtration of particles in Digital MicroFluidic (DMF) devices is presented in this work. In recent years there has been increased development of Lab-On-A-Chip (LOAC) devices for the automation and miniaturization of biological protocols. One platform for further research is in digital microfluidics. A digital microfluidic device can control the movement of pico-to nanoliter droplets of fluid using electrical signals without the use of pumps, valves, and channels. As such, fluidic pathways are not hardwired and the path of each droplet can be easily reconfigured. This is advantageous in biological protocols requiring the use of multiple reagents. Fabrication of these devices is relatively straight forward, since fluid manipulation is possible without the use of complex components. This work presents a method to characterize the performance of a digital microfluidic device using passive mechanical supernatant dilution via image analysis using a low cost vision system. The primary metric for performance of the device is particle retention after multiple passes through the filter. Repeatability of the process will be examined by characterizing performance of multiple devices using the same filter geometry. Qualitative data on repeatability and effectiveness of the dilution technique will also be attained by observing the ease with which the droplet disengages from the filter and by measuring the quantity of fluid trapped on the filter after each filtration step.

Micromachines ◽  
2018 ◽  
Vol 9 (8) ◽  
pp. 387
Author(s):  
Carlos Toshiyuki Matsumi ◽  
Wilson José da Silva ◽  
Fábio Kurt Schneider ◽  
Joaquim Miguel Maia ◽  
Rigoberto E. M. Morales ◽  
...  

Microbubbles have various applications including their use as carrier agents for localized delivery of genes and drugs and in medical diagnostic imagery. Various techniques are used for the production of monodisperse microbubbles including the Gyratory, the coaxial electro-hydrodynamic atomization (CEHDA), the sonication methods, and the use of microfluidic devices. Some of these techniques require safety procedures during the application of intense electric fields (e.g., CEHDA) or soft lithography equipment for the production of microfluidic devices. This study presents a hybrid manufacturing process using micropipettes and 3D printing for the construction of a T-Junction microfluidic device resulting in simple and low cost generation of monodisperse microbubbles. In this work, microbubbles with an average size of 16.6 to 57.7 μm and a polydispersity index (PDI) between 0.47% and 1.06% were generated. When the device is used at higher bubble production rate, the average diameter was 42.8 μm with increased PDI of 3.13%. In addition, a second-order polynomial characteristic curve useful to estimate micropipette internal diameter necessary to generate a desired microbubble size is presented and a linear relationship between the ratio of gaseous and liquid phases flows and the ratio of microbubble and micropipette diameters (i.e., Qg/Ql and Db/Dp) was found.


Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 707 ◽  
Author(s):  
Md Mubarak Hossain ◽  
Tanzilur Rahman

Micro-milling is one of the commonly used methods of fabrication of microfluidic devices necessary for cell biological research and application. Commercial micro-milling machines are expensive, and researchers in developing countries can’t afford them. Here, we report the design and the development of a low-cost (<130 USD) micro milling machine and asses the prototyping capabilities of microfeatures in plastic materials. We demonstrate that the developed machine can be used in fabricating the plastic based microfluidic device.


Lab on a Chip ◽  
2015 ◽  
Vol 15 (18) ◽  
pp. 3776-3784 ◽  
Author(s):  
Darius G. Rackus ◽  
Michael D. M. Dryden ◽  
Julian Lamanna ◽  
Alexandre Zaragoza ◽  
Brian Lam ◽  
...  

Nanostructured microelectrodes (NMEs) combined with digital microfluidics (DMF) for automated electroimmunoassays.


BioTechniques ◽  
2021 ◽  
Author(s):  
Vedika J Shenoy ◽  
Chelsea ER Edwards ◽  
Matthew E Helgeson ◽  
Megan T Valentine

3D printing holds potential as a faster, cheaper alternative compared with traditional photolithography for the fabrication of microfluidic devices by replica molding. However, the influence of printing resolution and quality on device design and performance has yet to receive detailed study. Here, we investigate the use of 3D-printed molds to create staggered herringbone mixers (SHMs) with feature sizes ranging from ∼100 to 500 μm. We provide guidelines for printer calibration to ensure accurate printing at these length scales and quantify the impacts of print variability on SHM performance. We show that SHMs produced by 3D printing generate well-mixed output streams across devices with variable heights and defects, demonstrating that 3D printing is suitable and advantageous for low-cost, high-throughput SHM manufacturing.


Micromachines ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1423
Author(s):  
Zhen Gu ◽  
Jing-Jing Luo ◽  
Le-Wei Ding ◽  
Bing-Yong Yan ◽  
Jia-Le Zhou ◽  
...  

Digital microfluidic (DMF) has been a unique tool for manipulating micro-droplets with high flexibility and accuracy. To extend the application of DMF for automatic and in-site detection, it is promising to introduce colorimetric sensing based on gold nanoparticles (AuNPs), which have advantages including high sensitivity, label-free, biocompatibility, and easy surface modification. However, there is still a lack of studies for investigating the movement and stability of AuNPs for in-site detection on the electrowetting-based digital microfluidics. Herein, to demonstrate the ability of DMF for colorimetric sensing with AuNPs, we investigated the electrowetting property of the AuNPs droplets on the hydrophobic interface of the DMF chip and examined the stability of the AuNPs on DMF as well as the influence of evaporation to the colorimetric sensing. As a result, we found that the electrowetting of AuNPs fits to a modified Young–Lippmann equation, which suggests that a higher voltage is required to actuate AuNPs droplets compared with actuating water droplets. Moreover, the stability of AuNPs was maintained during the processing of electrowetting. We also proved that the evaporation of droplets has a limited influence on the detections that last several minutes. Finally, a model experiment for the detection of Hg2+ was carried out with similar results to the detections in bulk solution. The proposed method can be further extended to a wide range of AuNPs-based detection for label-free, automatic, and low-cost detection of small molecules, biomarkers, and metal ions.


Author(s):  
Travis S. Emery ◽  
Anna Jensen ◽  
Koby Kubrin ◽  
Michael G. Schrlau

Three-dimensional (3D) printing is a novel technology whose versatility allows it to be implemented in a multitude of applications. Common fabrication techniques implemented to create microfluidic devices, such as photolithography, wet etching, etc., can often times be time consuming, costly, and make it difficult to integrate external components. 3D printing provides a quick and low-cost technique that can be used to fabricate microfluidic devices in a range of intricate geometries. External components, such as nanoporous membranes, can additionally be easily integrated with minimal impact to the component. Here in, low-cost 3D printing has been implemented to create a microfluidic device to enhance understanding of flow through carbon nanotube (CNT) arrays manufactured for gene transfection applications. CNTs are an essential component of nanofluidic research due to their unique mechanical and physical properties. CNT arrays allow for parallel processing however, they are difficult to construct and highly prone to fracture. As a means of aiding in the nanotube arrays’ resilience to fracture and facilitating its integration into fluidic systems, a 3D printed microfluidic device has been constructed around these arrays. Doing so greatly enhances the robustness of the system and additionally allows for the nanotube array to be implemented for a variety of purposes. To broaden their range of application, the devices were designed to allow for multiple isolated inlet flows to the arrays. Utilizing this multiple inlet design permits distinct fluids to enter the array disjointedly. These 3D printed devices were in turn implemented to visualize flow through nanotube arrays. The focus of this report though, is on the design and fabrication of the 3D printed devices. SEM imaging of the completed device shows that the nanotube array remains intact after the printing process and the nanotubes, even those within close proximity to the printing material, remain unobstructed. Printing on top of the nanotube arrays displayed effective adhesion to the surface thus preventing leakage at these interfaces.


Lab on a Chip ◽  
2015 ◽  
Vol 15 (1) ◽  
pp. 225-236 ◽  
Author(s):  
Steve C. C. Shih ◽  
Philip C. Gach ◽  
Jess Sustarich ◽  
Blake A. Simmons ◽  
Paul D. Adams ◽  
...  

We have developed a new hybrid droplet-to-digital microfluidic platform (D2D) that integrates droplet-in-channel microfluidics with digital microfluidics for performing multi-step single cell assays.


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