Automated Centrifugal-Microfluidic Platform for DNA Purification Using Laser Burst Valve and Coriolis Effect

Microvalves for Applications in Centrifugal Microfluidics

Centrifugal microfluidic platforms (CDs) have opened new possibilities for inexpensive point-of-care (POC) diagnostics. They are now widely used in applications requiring polymerase chain reaction steps, blood plasma separation, serial dilutions, and many other diagnostic processes. CD microfluidic devices allow a variety of complex processes to transfer onto the small disc platform that previously were carried out by individual expensive laboratory equipment requiring trained personnel. The portability, ease of operation, integration, and robustness of the CD fluidic platforms requires simple, reliable, and scalable designs to control the flow of fluids. Valves play a vital role in opening/closing of microfluidic channels to enable a precise control of the flow of fluids on a centrifugal platform. Valving systems are also critical in isolating chambers from the rest of a fluidic network at required times, in effectively directing the reagents to the target location, in serial dilutions, and in integration of multiple other processes on a single CD. In this paper, we review the various available fluidic valving systems, discuss their working principles, and evaluate their compatibility with CD fluidic platforms. We categorize the presented valving systems into either "active", "passive", or "hybrid"-based on their actuation mechanism that can be mechanical, thermal, hydrophobic/hydrophilic, solubility-based, phase-change, and others. Important topics such as their actuation mechanism, governing physics, variability of performance, necessary disc spin rate for valve actuation, valve response time, and other parameters are discussed. The applicability of some types of valves for specialized functions such as reagent storage, flow control, and other applications is summarized.

Fully Automated Lab-On-A-Disc Platform for Loop-Mediated Isothermal Amplification Using Micro-Carbon-Activated Cell Lysis

Fast and fully automated deoxyribonucleic acid (DNA) amplification methods are of interest in the research on lab-on-a-disc (LOD) platforms because of their full compatibility with the spin-column mechanism using centrifugal force. However, the standard procedures followed in DNA amplification require accurate noncontact temperature control as well as cell lysis at a low temperature to prevent damage to the LOD platform. This requirement makes it challenging to achieve full automation of DNA amplification on an LOD. In this paper, a fully automated LOD capable of performing cell lysis and amplification on a single compact disc of DNA samples is proposed. The proposed system uses micro-carbon to heat DNA samples without damaging the LOD as well as a noncontact heating system and an infrared camera sensor to remotely measure the real temperature of the amplification chamber. Compared with conventional DNA amplification systems, the proposed system has the advantage of full automation of the LOD platform. Experimental results demonstrated that the proposed system offers a stable heating method for DNA amplification and cell lysis.

Optical Temperature Control Unit and Convolutional Neural Network for Colorimetric Detection of Loop-Mediated Isothermal Amplification on a Lab-On-A-Disc Platform

Lab-on-a-disc (LOD) has emerged as a promising candidate for a point-of-care testing (POCT) device because it can effectively integrate complex fluid manipulation steps using multiple layers of polymeric substrates. However, it is still highly challenging to design and fabricate temperature measurement and heating system in non-contact with the surface of LOD, which is a prerequisite to successful realization of DNA amplification especially with a rotatable disc. This study presents a Lab-on-a-disc (LOD)-based automatic loop-mediated isothermal amplification (LAMP) system, where a thermochromic coating (<~420 µm) was used to distantly measure the chamber’s temperature and a micro graphite film was integrated into the chamber to remotely absorb laser beam with super high efficiency. We used a deep learning network to more consistently analyze the product of LAMP than we could with the naked eye. Consequently, both temperature heating and measurement were carried out without a physical contact with the surface of LOD. The experimental results show that the proposed approach, which no previous work has attempted, was highly effective in realizing LAMP in LOD.

Non-Contact Temperature Control System Applicable to Polymerase Chain Reaction on a Lab-on-a-Disc

Polymerase chain reaction (PCR) and the visual inspection of fluorescent amplicons for detection are commonly used procedures in nucleic acid tests. However, it has been extremely challenging to incorporate PCR onto a lab-on-a-disc (PCR-LOD) as it involves controlling the complicated and precise heating steps during thermal cycling and the measurement of reagent temperature. Additionally, a non-contact temperature control system without any connecting attachments needs to be implemented to facilitate the rotation of the PCR-LOD. This study presents a non-contact temperature control system to integrate conventional PCR onto an LOD. The experimental results demonstrate that our proposed system provides one-stop detection capabilities for Salmonella with a stable PCR amplification in a single PCR-LOD.

Binary centrifugal microfluidics enabling novel, digital addressable functions for valving and routing

Centrifugal microfluidics or lab-on-a-disc (LOAD) is a promising branch of lab-on-a-chip or microfluidics. Besides effective fluid transportation and inherently available density-based sample separation in centrifugal microfluidics, uniform actuation of flow on the disc makes the platform compact and scalable. However, the natural radially outward centrifugal force in a LOAD system limits its capacity to perform complex fluid manipulation steps. In order to increase the fluid manipulation freedom and integration capacity of the LOAD system, we propose a binary centrifugal microfluidics platform. With the help of Euler force, our platform allows free switching of both left and right states based on a rather simple mechanical structure. The periodical switching of state would provide a "clock" signal for a sequence of droplet binary logic operations. With the binary state platform and the "clock" signal, we can accurately handle the droplet separately in each time step with a maximum main frequency of about 10 S s-1 (switching per second). Apart from droplet manipulations such as droplet generation and metering, we also demonstrate a series of droplet logic operations, such as binary valving, droplet routing and digital addressable droplet storage. Furthermore, complex bioassays such as the Bradford assay and DNA purification assay are demonstrated on a binary platform, which is totally impossible for a traditional LOAD system. Our binary platform largely improves the capability for logic operation on the LOAD platform, and it is a simple and promising approach for microfluidic lab-on-a-disc large-scale integration.

Lab-on-a-Disc Platform for Automated Chemical Cell Lysis

Chemical cell lysis is an interesting topic in the research to Lab-on-a-Disc (LOD) platforms on account of its perfect compatibility with the centrifugal spin column format. However, standard procedures followed in chemical cell lysis require sophisticated non-contact temperature control as well as the use of pressure resistant valves. These requirements pose a significant challenge thereby making the automation of chemical cell lysis on an LOD extremely difficult to achieve. In this study, an LOD capable of performing fully automated chemical cell lysis is proposed, where a combination of chemical and thermal methods has been used. It comprises a sample inlet, phase change material sheet (PCMS)-based temperature sensor, heating chamber, and pressure resistant valves. The PCMS melts and solidifies at a certain temperature and thus is capable of indicating whether the heating chamber has reached a specific temperature. Compared to conventional cell lysis systems, the proposed system offers advantages of reduced manual labor and a compact structure that can be readily integrated onto an LOD. Experiments using Salmonella typhimurium strains were conducted to confirm the performance of the proposed cell lysis system. The experimental results demonstrate that the proposed system has great potential in realizing chemical cell lysis on an LOD whilst achieving higher throughput in terms of purity and yield of DNA thereby providing a good alternative to conventional cell lysis systems.