Microfluidics has achieved integration of analytical processes in microspaces and realized miniaturized analyses in fields such as chemistry and biology. We have proposed a general concept of integration and extended this concept to the 10-1000 nm scale exploring ultimate analytical performances (e.g. immunoassay of a single-protein molecule). However, a sampling method is still challenging for nanofluidics despite its importance in analytical chemistry. In this study, we developed a femtoliter (fL) sampling method for volume measurement and sample transport. Traditionally, sampling has been performed using a volumetric pipette and flask. In this research, a nanofluidic device consisting of a femtoliter volumetric pipette and flask was fabricated on glass substrates. Since gravity, which is exploited in bulk fluidic operations, becomes less dominant than surface effects on the nanometer scale, fluidic operation of the femtoliter sampling was designed utilizing surface tension and air pressure control. The working principle of an 11 fL volumetric pipette and a 50 fL flask, which were connected by a nanochannel, was verified. It was found that evaporation of the sample solution by air flow was a significant source of error because of the ultra-small volumes being processed. Thus, the evaporation issue was solved by suppressing the air flow. As a result, the volumetric measurement error was decreased to ±0.06 fL (CV 0.6%), which is sufficiently low for use in nanofluidic analytical applications. This study will present a fundamental technology for the development of novel analytical methods for femtoliter volume samples such as single molecule analyses.
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http://dx.doi.org/10.1039/c9an02258a | DOI Listing |
Lab Chip
June 2024
Department of Biomechatronics Engineering, National Taiwan University, Taipei, Taiwan, R.O.C.
Microfluidic dispensing technologies often require additional equipment, posing challenges for their integration into point-of-care testing (POCT) applications. In response to this challenge, we have developed a pipette-operable microfluidic device fabricated using 3D printing technology for precise liquid dispensing. This device features three reaction chambers and three distinct hydrophobic valves to control the flow direction of liquids.
View Article and Find Full Text PDFAnalyst
November 2023
School of Chemistry and Chemical Engineering, Ankang University, Quality Supervision and Inspection Centre of Se-enriched Food of Shaanxi Province, Shaanxi University Innovation Research Institute of Advanced Energy Storage Materials and Battery Technology for Future Industrialization, Ankang Research Centre of New Nano-materials Science and Technology Research Centre, Ankang, Shaanxi Province, 725000, P. R. China.
On the basis of the "seeing is believing" concept and the existing theory of Hg coordination chemistry, for the first time, we innovatively designed and synthesized a visual-volumetric sensor platform with fluorescein and uracil functionalized polyacrylamide hydrogel. Without the aid of any complicated instruments and power sources, the sensor-enabled quantitative μM-level Hg detection Hg by reading graduation on a pipette with the naked eye. The sensor undergoes volumetric response and shows a wide linear response range to Hg (1.
View Article and Find Full Text PDFRev Sci Instrum
September 2023
Department of Precision Machinery and Precision Instrumentation, University of Science and Technology of China, Hefei 230027, Anhui, China.
Liquid handling is a necessary act to deal with liquid samples from scientific labs to industry. However, existing pipetting devices suffer from inaccuracy and low precision when dealing with submicroliter liquids, which significantly affect their applications in low-volume quantitation. In this article, we present an automated liquid pipetting device that can aspirate liquid from microplates and dispense nanoliter droplets with high precision.
View Article and Find Full Text PDFLab Chip
March 2023
Biomedical Engineering Department, McGill University, 740 Dr. Penfield Ave, Montreal, QC, H3A 0G1, Canada.
Sandwich immunoassays such as the enzyme-linked immunosorbent assay (ELISA) have been miniaturized and performed in a lab-on-a-chip format, but the execution of the multiple assay steps typically requires a computer or complex peripherals. Recently, an ELISA for detecting antibodies was encoded structurally in a chip thanks to the microfluidic chain reaction (Yafia , 2022, , 464-469), but the need for precise pipetting and intolerance to commonly used surfactant concentrations limit the potential for broader adoption. Here, we introduce the ELISA-on-a-chip with aliquoting functionality that simplifies chip loading and pipetting, accommodates higher surfactant concentrations, includes barrier channels that delay the contact between solutions and prevent undesired mixing, and that executed a quantitative, high-sensitivity assay for the SARS-CoV-2 nucleocapsid protein in 4×-diluted saliva.
View Article and Find Full Text PDFJ Diabetes Sci Technol
May 2024
UTSAAH Lab, Center for Product Design and Manufacturing, Indian Institute of Science, Bangalore, India.
Background: A wide suite of methods are available to evaluate delivery accuracy of insulin pumps. However, these methods do not capture any temporal information, which may be critical for design of artificial pancreas (AP) systems. We propose a novel video microscopy method to understand the delivery accuracy and temporal nature for a new durable pump under development (IFP), and a commercially available pump (Medtronic 722G, M722G).
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