Biology subjects

Leong, K. M.

Publications and source records attributed to Leong, K. M..

3 recordsLinked to original sources

bioRxiv2025

CandyCollect Open to Closed (O2C) Microfluidic System for Rapid and User-Centric Detection of Group A Streptococcus

We created CandyCollect, a lollipop-inspired, child-friendly saliva sampling device that provides enhanced comfort compared to common throat and mouth swabs. The device has an open microchannel and a functionalized surface that effectively captures and stores the saliva and pathogens. We recently demonstrated the ability to combine the CandyCollect with rapid antigen detection tests (RADTs) for fast and accessible detection of group A streptococcus (GAS). However, the current procedure necessitates manual steps to elute and transfer captured antigens from the lollipop to RADTs, which relies on the user to follow complex instructions, increasing the likelihood of error. In this work, we developed the CandyCollect Open to Closed (O2C) microfluidic system to automate antigen elution and streamline detection with RADTs. The O2C system securely seals the open microchannels of the CandyCollect device to create a continuous closed channel for seamless delivery of elution reagents to release antigens at the press of a button for subsequent lateral flow detection. Our system leverages and combines the unique benefits of both open channel and closed channel microfluidics into one platform, further enhancing the potential of both methods. We performed experiments with GAS bacteria spiked into saliva and compared the manual and O2C elution methods. Both the manual and O2C methods showed clear test lines on the RADT strips at clinically relevant GAS concentrations (between 5 x105 and 109 CFU/mL). The O2C provided comparable or better results than the manual procedure in a more convenient form factor. The O2C platform has the potential to enable user-friendly screening for respiratory pathogens by minimally trained users in decentralized settings.

bioengineering↗

bioRxiv2024

Expanding the capillarics toolbox: 3D-printed microfluidic phaseguides and self-coalescence modules

Capillarics are microfluidic circuits that are assembled from individual fluidic elements, powered by surface tension forces encoded by microchannel geometry and surface chemistry, and enable instrument-free pre-programmed automation of multi-step liquid handling processes. 3D printing has recently transformed capillarics by enabling rapid and cost-effective prototyping, provided addition geometric degrees of freedom in multi-level fabrication, and facilitated new design paradigms with greater capabilities than traditional cleanroom fabrication. Despite widespread interest in 3D printing and development of custom high-resolution stereolithography printers for microfluidic applications, fluidic elements that require precise and tunable control over capillary pinning lines -- such as fluidic phaseguides and self-coalescence modules (SCMs) -- have so far only been manufactured with centralized and expensive cleanroom methods. Not only does this limit access to versatile capillaric features to only well-resourced settings, but it also slows innovation and widespread application of these fluid handling technologies. Here we expand the toolbox of 3D-printed capillarics to include phaseguides and SCMs, demonstrating their potential for precise instrument-free control over multi-step liquid handling and reagent rehydration. We employed benchtop stereolithography printers to prototype (up to 50X) scaled-up phaseguides and SCMs and integrated them into a capillaric circuit for inline reagent reconstitution, dynamic fluid control, and sequential drainage. We showcased scalable designs, customizable geometries, and robust self-coalescing flow for larger liquid volumes -- up to 50 L compared with 1.25 L in cleanroom-fabricated SCMs. This work represents a significant advance in democratizing access to microfluidics, with potential for broad applications in diagnostics, assay automation, and organ-on-chip systems.

bioengineering↗

bioRxiv2023

Democratizing access to microfluidics: Rapid prototyping of capillary microfluidics with a low-cost masked stereolithography 3D printer

Microfluidics offer user-friendly liquid handling for a range of biochemical applications. 3D printing microfluidics is rapid and cost-effective compared to conventional cleanroom fabrication. Typically, microfluidics are 3D printed using digital light projection (DLP) stereolithography (SLA), but many models in use are expensive ([≥]$10,000 USD), limiting widespread use. Recent liquid crystal display (LCD) technology advancements have provided inexpensive (<$500) SLA 3D printers with sufficient pixel resolution for microfluidic applications. However, there are only a few demonstrations of microfluidic fabrication, limited validation of print fidelity, and no direct comparisons between LCD and DLP printers. We compared a 40 {micro}m pixel resolution DLP printer ([~]$18,000 USD) with a 34.4 {micro}m (<$380) LCD-SLA printer. Consistent with prior work, we observed linear trends between designed and measured channel widths [≥] 4 pixels on both printers, so we calculated accuracy above this size threshold. Using a standard IPA wash resin and optimized parameters for each printer, the average error between designed and measured widths was 2.11 {+/-} 1.26% with the DLP printer and 15.4 {+/-} 2.57% with the 34.4 {micro}m LCD printer. The average coefficient of variation [CV] was [~]2% for both printers. Printing with optimized conditions for a low-cost water wash resin designed for LCD-SLA printers resulted in an average error of 2.53 {+/-} 0.94% with the 34.4 {micro}m LCD printer and 5.35 {+/-} 4.49% with a 22 {micro}m LCD printer. We characterized additional parameters including surface roughness, channel perpendicularity, and light intensity uniformity, and as an application of LCD-printed devices, we demonstrated consistent flow rates in capillaric circuits for self-regulated and self-powered delivery of multiple liquids. In conclusion, LCD printers are an inexpensive alternative for fabricating microfluidics, with minimal differences in fidelity and accuracy compared with a 20X more expensive DLP printer.

scientific communication and education↗