Nanoliter: The Tiny Volume Driving Advances in Microfluidics and Bioengineering

A nanoliter (nL) is an extremely small unit of volume equal to one billionth of a liter or one thousandth of a microliter. To put this minuscule volume into perspective, a single drop of water contains approximately 50,000 nanoliters. The nanoliter scale is crucial in various fields, including microfluidics, bioengineering, and nanotechnology, where precise control over tiny volumes is essential for applications such as drug delivery, single-cell analysis, and lab-on-a-chip devices.

Working with nanoliter volumes requires specialized devices and techniques capable of precise fluid handling and manipulation. Some key tools and methods used in nanoliter-scale research include:

Microfluidic chips are miniaturized devices that contain micro-channels, valves, and pumps for handling and processing nanoliter-scale fluid volumes. These chips are fabricated using techniques such as soft lithography and can be made from materials like polydimethylsiloxane (PDMS) or glass. Microfluidic chips enable the integration of multiple laboratory functions, such as sample preparation, reaction, separation, and detection, onto a single platform, reducing reagent consumption and analysis time.

Nanoliter dispensing involves the precise delivery of nanoliter-sized droplets using specialized equipment such as piezoelectric or solenoid valve dispensers. These instruments can accurately dispense volumes as low as 0.1 nanoliters, enabling the preparation of high-density microarrays, the spotting of biological samples, and the dosing of drugs or chemicals in miniaturized assays.

Nanoliter-scale compartments, such as droplets, emulsions, or microwells, provide isolated environments for studying individual cells, molecules, or reactions. These compartments can be generated using microfluidic devices or surface patterning techniques and offer several advantages, including high throughput, reduced cross-contamination, and the ability to perform single-cell analysis.

Nanoliter-scale technologies have found widespread applications across various fields, revolutionizing the way we study biological systems, develop new drugs, and perform chemical and biochemical analyses. Some key application areas include:

Nanoliter-scale technologies enable high-throughput drug screening and optimization by minimizing reagent consumption and allowing for the parallel testing of thousands of compounds. Microfluidic devices can be used to generate nanoliter-sized droplets containing different drug candidates and cell samples, facilitating the rapid identification of promising lead compounds and the assessment of drug efficacy and toxicity.

Nanoliter-scale compartments, such as microfluidic droplets or microwells, provide an ideal platform for single-cell analysis, allowing researchers to study cellular heterogeneity and uncover rare cell types or behaviors. By encapsulating individual cells in nanoliter volumes, one can perform high-throughput single-cell RNA sequencing, proteomics, or functional assays, leading to new insights into cellular processes and disease mechanisms.

Nanoliter-scale technologies are playing an increasingly important role in the development of point-of-care diagnostic devices. By integrating sample preparation, reaction, and detection steps onto a single microfluidic chip, it is possible to create portable and low-cost diagnostic platforms that require only nanoliter volumes of patient samples. These devices can be used for the rapid detection of infectious diseases, the monitoring of chronic conditions, or the screening of genetic disorders, improving access to healthcare in resource-limited settings.

Despite the numerous advantages of nanoliter-scale technologies, there are still challenges to be addressed. One of the main challenges is the scalability and manufacturing of microfluidic devices, as current fabrication methods often rely on complex and costly processes. Efforts are being made to develop new materials and fabrication techniques that enable the mass production of nanoliter-scale devices at lower costs.

Another challenge is the integration of nanoliter-scale technologies with other analytical techniques, such as mass spectrometry or optical imaging, to provide comprehensive characterization of biological samples. Researchers are working on developing novel interfaces and coupling strategies to seamlessly combine nanoliter-scale sample handling with advanced detection methods.

As nanoliter-scale technologies continue to evolve, we can expect to see more sophisticated and integrated devices that enable the study of complex biological systems, the discovery of new drugs, and the development of personalized medicine. The convergence of microfluidics, nanotechnology, and bioengineering will likely lead to transformative advances in healthcare, environmental monitoring, and chemical synthesis, with nanoliter volumes playing a central role in driving these innovations.

Small, Nanoliter Scale Parallel Liquid–Liquid Extraction for High-Throughput Purification on a Droplet Microarray

TrAC Trends in Analytical Chemistry, Automated, flexible and versatile manipulation of nanoliter-to-picoliter droplets based on sequential operation droplet array technique

PNAS, Combinatorial drug discovery in nanoliter droplets