Tiny stamps for tiny sensors
Researchers at MIT develop new glass stamp that may make cheaper, more precise biosensors
Story content courtesy of MIT
Researchers at MIT have come up with a simple, precise and reproducible technique that cuts the time and cost of fabricating such sensors. Nicholas Fang, associate professor of mechanical engineering, has developed an engraving technique that etches tiny, nano-sized patterns on metallic surfaces using a small, voltage-activated stamp made out of glass. Fang says the engravings, made of tiny dots smaller than one-hundredth the width of a human hair, act as optical antennae that can identify a single molecule by picking up on its specific wavelength.
The new glass stamp approach may help researchers clear a large hurdle in lab-on-a-chip manufacturing: namely, scale-up. Today scientists fabricate nano-sensors using electron-beam lithography, an expensive and time-consuming technique that uses a focused beam of electrons to slowly etch patterns into metallic surfaces. The process, while extremely precise, is also extremely expensive.
Fang and his colleagues came up with a technique that may solve the cost, precision and reproducibility issues of other technologies. The team took an approach similar to nanoimprint lithography. But instead of polymer, the researchers used glass as a molding material. “I was inspired by glassblowers, who actually use their skills to form bottles and beakers,” Fang says. “Even though we think of glass as fragile, at the molten stage, it is actually very malleable and soft, and can quickly and smoothly take the shape of a plaster mold.
The researchers filled a small syringe with glass particles and heated the needle to melt the glass inside. They then pressed the molten glass onto a master pattern, forming a mold that hardened when cooled. The team then pressed the glass mold onto a flat silver substrate, and applied a small, 90-millivolt electric potential above the silver layer. The voltage stimulated ions in both surfaces, and triggered the glass mold to essentially etch into the metal substrate.
The group was able to produce patterns of tiny dots, 30 nanometers wide, in patterns of triangles, rectangles and, playfully, an ionic column, at a resolution more precise than nanoimprint lithography.