A tool box may be equipped with multi-purpose instruments but their use is restricted to repairing or creating objects that are relatively simpler than nanoparticles. The research team at NIST has surfaced with a miniature multi-tool which is a nanoscale fluidic equipment engineered for working with nanoparticles.
The team first crafted a 3D nanofluidic staircase channel with many depths to separate and calculate a mixture of different-sized fluorescent nanoparticles. The particles that were larger were brighter than the small, dim ones. These particles were then pushed towards the shallow side of the channel which then stopped at the steps of the staircase according to their sizes.
The device is made up of cascading staircase of 30 nanofluidic channels that range from about 80 nanometers at the top to about 620 nanometers at the bottom in depth. Each of these steps functions as a tool of a different size to maneuver nanoparticles. The study shows that the device can carry out nanoscale tasks of separating and measuring a mixture of spherical nanoparticles differing in size and dispersed in a solution.
The team employed electrophoresis to move the charged particles through a solution by pushing them ahead with an applied electric field. This drives the nanoparticles present in the deep end of the chamber across the device into the shallower channels. Additionally, the nanoparticles were assigned fluorescent colors to track them through a microscope.
It was noted that the larger particles stopped on reaching the steps of the staircase with depths that matched their diameters of around 220 nanometers. The smaller particles kept moving till they were restricted from entering shallower channels at depths of around 110 nanometers.
The position of every particle could be mapped to the corresponding channel depth thanks to their fluorescent points of light. The researchers could then gauge the distribution of nanoparticle sizes and assert the utility of the device as a separation tool and reference material. This method would make it easier to separate intricate mixtures when integrated in a microchip.
The researchers believe that this method could be faster and more economical as opposed to conventional methods of nanoparticle sample preparation and characterization. The team plans to design nanofluidic devices for different nanoparticle sorting applications. These devices could be crafted with customized resolution over a particular range of particle sizes and for select materials. Moreover, the team aims to invent a technique to separate mixtures of nanoparticles with similar sizes but different shapes.
The study has been mentioned in a new article in the journal Lab on a Chip.