Applied physicists and materials scientists from Harvard's School of Engineering and Applied Sciences (SEAS) have discovered a new device capable of identifying an unknown fluid. This palm fitting device utilizes the optical and chemical properties of high-precision nanostructured materials to differentiate fluids through their surface tension without using a power source.
Similar to litmus paper used in labs, this novel device shows a change in color while contacting a fluid with a specific surface tension. Individual chips react in different ways to several substances and can also differentiate between two liquids that are closely related. Ian B. Burgess, a doctoral candidate in Lonèar's lab, stated that the fluidic and optical properties used in this study were unique to the material’s three-dimensional nanostructure. It is possible to actually “write” a secret message on the chip which will be seen only when it is exposed to the right material.
The concept, Watermark Ink or W-Ink used in this study is based on a specifically fabricated material known as an inverse opal, a layered glass structure containing an intricate network of interconnected and ordered air pores. Burgess and his team demonstrated that selective treating of inverse opal parts with oxygen plasma and vaporized chemicals causes changes in channels and pores’ reactive properties, allowing only specific liquids to pass through and preventing the others.
The optical properties of a material changes when liquid is made to pass through its pores, thus the inverse opal’s natural color is visible only in dry places. Each three-dimensional nanostructured chip is regulated to identify only specific liquids, but can be utilized repeatedly during the test process.
This W-Ink technology allows authorities to check gasoline’s fuel grade exactly at the pump. Additionally, this will be helpful to identify chemical spillages rapidly. A W-Ink chip calibrated to identify several toxic agents can be utilized to determine the requirement of special treatment for spill instantly.
Source: http://www.harvard.edu/