Rapid prototyping of low-cost digital microfluidic devices using laser ablation

In the last decade microfabrication processes including rapid prototyping techniques have advanced rapidly and achieved a fairly mature stage. These advances have encouraged and enabled the use of microfluidic devices by a wider range of users with applications in biological separations and cell and organoid cultures. Accordingly, a significant current challenge in the field is controlling biomolecular interactions at interfaces and the development of novel biomaterials to satisfy the unique needs of the biomedical applications. Poly(dimethylsiloxane) (PDMS) is one of the most widely used materials in the fabrication of microfluidic devices. The popularity of this material is the result of its low cost, simple fabrication allowing rapid prototyping, high optical transparency, and gas permeability. However, a major drawback of PDMS is its hydrophobicity and fast hydrophobic recovery after surface hydrophilization. This results in significant nonspecific adsorption of proteins as well as small hydrophobic molecules such as therapeutic drugs limiting the utility of PDMS in biomedical microfluidic circuitry. Accordingly, here, we focus on recent advances in surface molecular treatments to prevent fouling of PDMS surfaces towards improving its utility and expanding its use cases in biomedical applications.

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Negligible-cost microfluidic device fabrication using 3D-printed interconnecting channel scaffolds

PLoS ONE ◽

10.1371/journal.pone.0245206 ◽

2021 ◽

Vol 16 (2) ◽

pp. e0245206

Author(s):

Harry Felton ◽

Robert Hughes ◽

Andrea Diaz-Gaxiola

Keyword(s):

Rapid Prototyping ◽

Point Of Care ◽

Low Cost ◽

Microfluidic Channel ◽

Microfluidic Devices ◽

Device Fabrication ◽

Appropriate Technology ◽

Channel Cross Section ◽

Microfluidic Systems ◽

3D Printed

This paper reports a novel, negligible-cost and open-source process for the rapid prototyping of complex microfluidic devices in polydimethylsiloxane (PDMS) using 3D-printed interconnecting microchannel scaffolds. These single-extrusion scaffolds are designed with interconnecting ends and used to quickly configure complex microfluidic systems before being embedded in PDMS to produce an imprint of the microfluidic configuration. The scaffolds are printed using common Material Extrusion (MEX) 3D printers and the limits, cost & reliability of the process are evaluated. The limits of standard MEX 3D-printing with off-the-shelf printer modifications is shown to achieve a minimum channel cross-section of 100×100 μm. The paper also lays out a protocol for the rapid fabrication of low-cost microfluidic channel moulds from the thermoplastic 3D-printed scaffolds, allowing the manufacture of customisable microfluidic systems without specialist equipment. The morphology of the resulting PDMS microchannels fabricated with the method are characterised and, when applied directly to glass, without plasma surface treatment, are shown to efficiently operate within the typical working pressures of commercial microfluidic devices. The technique is further validated through the demonstration of 2 common microfluidic devices; a fluid-mixer demonstrating the effective interconnecting scaffold design, and a microsphere droplet generator. The minimal cost of manufacture means that a 5000-piece physical library of mix-and-match channel scaffolds (100 μm scale) can be printed for ~$0.50 and made available to researchers and educators who lack access to appropriate technology. This simple yet innovative approach dramatically lowers the threshold for research and education into microfluidics and will make possible the rapid prototyping of point-of-care lab-on-a-chip diagnostic technology that is truly affordable the world over.

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

Volume 7: Fluids Engineering Systems and Technologies ◽

10.1115/imece2014-38875 ◽

2014 ◽

Author(s):

Peter D. Dunning ◽

Pierre E. Sullivan ◽

Michael J. Schertzer

Keyword(s):

Microfluidic Device ◽

Vision System ◽

Low Cost ◽

Digital Microfluidics ◽

Microfluidic Devices ◽

Comb Filter ◽

Enzyme Linked Immunosorbent Assay ◽

Reaction Site ◽

Digital Microfluidic

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.

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A cost-effective micromilling platform for rapid prototyping of microdevices

TECHNOLOGY ◽

10.1142/s2339547816200041 ◽

2016 ◽

Vol 04 (04) ◽

pp. 234-239 ◽

Cited By ~ 10

Author(s):

Daniel P. Yen ◽

Yuta Ando ◽

Keyue Shen

Keyword(s):

Rapid Prototyping ◽

Low Cost ◽

Lab On A Chip ◽

Microfluidic Devices ◽

Cost Effective ◽

Multi Scale ◽

Organ On A Chip

Micromilling has great potential in producing microdevices for lab-on-a-chip and organ-on-a-chip applications, but has remained under-utilized due to the high machinery costs and limited accessibility. In this paper, we assessed the machining capabilities of a low-cost 3-D mill in polycarbonate material, which were showcased by the production of microfluidic devices. The study demonstrates that this particular mill is well suited for the fabrication of multi-scale microdevices with feature sizes from micrometers to centimeters.

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Low-cost rapid prototyping of glass microfluidic devices using a micromilling technique

Microfluidics and Nanofluidics ◽

10.1007/s10404-018-2104-y ◽

2018 ◽

Vol 22 (8) ◽

Cited By ~ 7

Author(s):

Xiaoyong Ku ◽

Zongwei Zhang ◽

Xiaolong Liu ◽

Li Chen ◽

Gang Li

Keyword(s):

Rapid Prototyping ◽

Low Cost ◽

Microfluidic Devices

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Comparison of Microscale Rapid Prototyping Techniques for Microfluidic Applications

Volume 1: Materials; Micro and Nano Technologies; Properties, Applications and Systems; Sustainable Manufacturing ◽

10.1115/msec2014-3932 ◽

2014 ◽

Cited By ~ 1

Author(s):

Gordon D. Hoople ◽

David A. Rolfe ◽

Katherine C. McKinstry ◽

Joanna R. Noble ◽

David A. Dornfeld ◽

...

Keyword(s):

Surface Roughness ◽

Laser Ablation ◽

Rapid Prototyping ◽

Microfluidic Devices ◽

Optical Microscope ◽

Microfluidic Channels ◽

Recent Developments ◽

3D Printed ◽

Small Feature ◽

Scanning Electron

Recent developments in microfluidics have opened up new interest in rapid prototyping with features on the microscale. Microfluidic devices are traditionally fabricated using photolithography, however this process can be time consuming and challenging. Laser ablation has emerged as the preferred solution for rapid prototyping of these devices. This paper explores the state of rapid prototyping for microfluidic devices by comparing laser ablation to micromilling and 3D printing. A microfluidic sample part was fabricated using these three methods. Accuracy of the features and surface roughness were measured using a surface profilometer, scanning electron microscope, and optical microscope. Micromilling was found to produce the most accurate features and best surface finish down to ∼100 μm, however it did not achieve the small feature sizes produced by laser ablation. 3D printed parts, though easily manufactured, were inadequate for most microfluidics applications. While laser ablation created somewhat rough and erratic channels, the process was within typical dimensions for microfluidic channels and should remain the default for microfluidic rapid prototyping.

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