A team of scientists has made valves which can operate on tiny channels of fluid the width of 3 human hairs! This paper, published in the Journal of Biomedical Microdevices, represents a step forward in lab technology. Creating a tiny valve like this could have important implications for cancer research, where fluids need to be controlled on a small scale. But what kinds of fluids?

Tumors, or clumps of cancer cells, are identified by using a special chemical fluid, known as a stain, so that they are easier to see. There are many different types of stains that test for different types of cancers. Traditionally, in the lab, in order to stain a cell with many different stains, someone has to manually add small amounts of each individual stain. Humans tend to make errors, so the scientists wondered how they could identify cancer cells more quickly, accessibly, and with greater accuracy than current methods.

This is what we mean by “cell stain.” Cells are normally clear. To be seen, they have to be colored and viewed under a microscope. The red in this photo is a type of cancer cell, photographed under a microscope. Source: Ed Uthman, Squamous Cell Carcinoma, Bronchial Washing, Pap Stain

To answer these questions, they designed and built an automatic dispenser system that could dispense each stain individually. This automatic dispenser is where the tiny valves come in.

The microvalve design consists of two pieces of glass with a thin silicone membrane in between. On one side of the membrane, the surface of the glass has many channels for holding fluid. The other side of the membrane contains corresponding channels for air. The air channels are aligned over the fluid channels such that pressing down on the membrane through the air channel would push the membrane into the fluid channel, creating a valve. Since the channels are independent of one another, each one can be filled with a different stain. 

The valve is operated by filling the air channels with pressurized air. Like blowing in a balloon, the membrane stretches and fills the space of the fluid channel. Just like turning a valve at a sink all the way off, this effectively blocks off fluid from flowing out to the piece of cancer sample. When the pressure is released, the membrane will snap back to its original position, opening the channel back up again.

The team of scientists wrote a computer program so that the computer could communicate with the equipment and open and close the valves individually. By automating the process of opening and closing the fluid channels, the staining process was sped up dramatically. Many stains could be applied at the same time, rather than having a person manually add each stain after the other.

Once the staining process was complete, the scientists looked at the stains through a fluorescent microscope. The stains that were stuck on cancer cells lit up, successfully identifying which type of cancer they were.

The authors concluded that the use of this automatic stain dispenser system can cheaply, quickly, successfully, and efficiently be used for tumor identification. This invention may lead to more advances  in tiny parts for fluid systems.