Picoliter liquid handling at gas/liquid interface by surface and geometry control in a micro-nanofluidic device

In micro- and nanofluidic devices, highly precise fluidic control is essential. Conventional mechanical valves in microchannels and nanochannels have size limitations, whereas hydrophobic (Laplace) valves are generally difficult to use for low-surface-tension liquids. In the present study, we developed a method for handling picoliter volumes of low-surface-tension liquids in a micro-nanofluidic device. The proposed Laplace valve is based on the pinning effect. A fused silica micro-nanofluidic device that includes a picoliter chamber whose geometry was designed to induce capillary pinning was designed and fabricated. The measured Laplace pressure of a lysis buffer (surfactant) was consistent with the calculated pressure, indicating successful fabrication and hydrophobic surface modification. The working principle of the Laplace valve was verified. The Laplace valve maintained the lysis buffer at the gas/liquid interface for 60 min, which is sufficiently long for cell lysis operations. Finally, replacement of liquids in the picoliter chamber using the valve was demonstrated. The proposed method will contribute to basic technologies for fluidic control in micro- and nanofluidic devices, and the proposed Laplace valve can be used for low-surface-tension liquids. In addition, the developed valve and picoliter chamber can be utilized for the interface in single-cell lysis, which will facilitate the development of single-cell analysis devices.

A Parallelized Nanofluidic Device for High-Throughput Optical DNA Mapping of Bacterial Plasmids

Optical DNA mapping (ODM) has developed into an important technique for DNA analysis, where single DNA molecules are sequence-specifically labeled and stretched, for example, in nanofluidic channels. We have developed an ODM assay to analyze bacterial plasmids—circular extrachromosomal DNA that often carry genes that make bacteria resistant to antibiotics. As for most techniques, the next important step is to increase throughput and automation. In this work, we designed and fabricated a nanofluidic device that, together with a simple automation routine, allows parallel analysis of up to 10 samples at the same time. Using plasmids encoding extended-spectrum beta-lactamases (ESBL), isolated from Escherichia coli and Klebsiella pneumoniae, we demonstrate the multiplexing capabilities of the device when it comes to both many samples in parallel and different resistance genes. As a final example, we combined the device with a novel protocol for rapid cultivation and extraction of plasmids from fecal samples collected from patients. This combined protocol will make it possible to analyze many patient samples in one device already on the day the sample is collected, which is an important step forward for the ODM analysis of plasmids in clinical diagnostics.

A nanofluidic device for rapid and multiplexed SARS-CoV-2 serological antibody detection

The outbreak of COVID-19 has led to a substantial death toll and has hindered the functioning of modern society, sending the world into a medical and economic crisis1,2. This underlined the importance of point-of-care diagnostics, as well as accurate, cost-effective serological antibody tests as well as point-of-care diagnostics to monitor the viral spread and contain pandemics and endemics. Here, we present a three-dimensional (3D) nanofluidic device for rapid and multiplexed detection of viral antibodies. The device is designed to size-dependently immobilize particles from a multi-particle mixture at predefined positions in nanochannels through capillary forces only, resulting in distinct trapping lines. We show that individual lines can be used as an on-chip fluorescence-linked immunosorbent assay for multiplexed detection of serological immunoglobulin antibodies against viral proteins with high sensitivity. Further device versatility is exhibited by on-bead color multiplexing for simultaneous detection of IgG and IgM antibodies in convalescent human serum and by concurrent detection of anti-spike (SARS-CoV-2) and anti-hemagglutinin (Influenza A) antibodies. The device’s applications can be further extended to detect a plethora of diseases simultaneously in a reliable and straightforward manner.

Eco friendly nanofluidic platforms using biodegradable nanoporous materials

Splendid advancement of micro/nanofluidic researches in the field of bio- and chemical-analysis enables various ubiquitous applications such as bio-medical diagnostics and environmental monitoring, etc. In such devices, nanostructures are the essential elements so that the nanofabrication methods have been major issues since the last couple of decades. However, most of nanofabrication methods are sophisticated and expensive due to the requirement of high-class cleanroom facilities, while low-cost and biocompatible materials have been already introduced in the microfluidic platforms. Thus, an off-the-shelf and biodegradable material for those nanostructures can complete the concept of an eco-friendly micro/nanofluidic platform. In this work, biodegradable materials originated from well-known organisms such as human nail plate and denatured hen egg (albumen and yolk) were rigorously investigated as a perm-selective nanoporous membrane. A simple micro/nanofluidic device integrated with such materials was fabricated to demonstrate nanofluidic phenomena. These distinctive evidences (the visualization of ion concentration polarization phenomenon, ohmic/limiting/over-limiting current behavior and surface charge-governed conductance) can fulfill the requirements of functional nanostructures for the nanofluidic applications. Therefore, while these materials were less robust than nano-lithographically fabricated structures, bio-oriented perm-selective materials would be utilized as a one of key elements of the biodegradable and eco friendly micro/nanofluidic applications.

A nanofluidic device for ultrasensitive and label-free detection of tetracycline in association with γ-cyclodextrin and GO

We develop a label-free, sensitive and selective nanochannel sensing platform for detection of TC. The nanosensor provided a low detection limit, a wide detection range and excellent recovery rate in different water samples.