A new inexpensive nanoglue that becomes stronger as it heats up could redefine the way computer chips are made and even pave the way for Spiderman-esque web-shooting devices in the near future, according to its creator.
Developed by a group of US researchers led by Rensselaer Polytechnic Institute's materials science and engineering professor, Ganapathiraman Ramanath, the new nanoglue is made from commercially available ultrathin glue materials that when heated to extreme temperatures can bond materials that don't usually stick together.
The underlying technology is known as nanolayers, which in essence are molecular chains with a backbone of carbon molecules, tail-ended with certain elements such as silicon, oxygen or sulfur. These molecules that sit on the end of the nanolayer act as hooks that bind with other surfaces.
Although these nanoylayers can improve adhesion and prevent materials from mixing together, they tend to lose their effectiveness and degrade or completely detach from a surface when heated above 400 degrees Celsius, Ramanath said.
However, after working with the material for over eight years in an attempt to discover new ways to improve the structural integrity of semiconductor devices in computer chips, Ramanath and his team discovered that a new heating process actually improved the adhesive properties of the nanolayers. Like many great inventions, Ramanath and his team happened upon the discovery by fluke.
Knowing that certain materials bonded together better than others, Ramanath sandwiched a nanolayer of commercially available glue between a thin film of copper and silica to strengthen the nanolayer's bonds and make it stickier. But when heated between 400 and 700 degrees Celsius, the nanolayer's molecules, sandwiched in between the copper and silica, formed an unexpectedly strong nanoglue which was much stronger than usual, increasing stickiness by five to seven times.
"The higher you heat it, the stronger the bonds get," said Ramanath. "When we first started out, I had not imagined the molecules behaving this way."
To make sure it wasn't a fluke, his team recreated the test more than 50 times over the past two years and achieved consistent results.
Ramanath said the nanoglue could be used in a number of applications from next-generation computer chip manufacturing to energy production. He even hypothesized that the super-adhesive properties of the nanoglue could be used to one day create a super-sticky web-shooting device much like the comic-book hero Spiderman's, an announcement sure to prick the ears of Peter Parker aficionados the globe over.
"If we can find a way to create threads and/or intertwined bundles using the molecules in a scalable fashion, while retaining the adhesive properties, then creating web-shooters similar to Spiderman's is a real possibility," he said. "There are ways in which molecular threads/bundles can be created in large quantities. The challenge will be, however, to simultaneously engineer adhesion on certain surfaces (and not others, since we want the suit only to form on the desired surface) and also with each other during the thread formation."
Ramanath was hesitant to elaborate further on the specifics of such a device as he and his team are currently experimenting to explore this type of application.
Spiderman schemes aside, Ramanath said the most practical use would be in the production of computer chips, to fortify metal-insulator interfaces in the wiring architectures of integrated circuits.
In such integrated circuits, copper wires are currently used to transport electrons within an insulating material, usually silica. While copper is a good diffuser of electrons, it does not stick well to the insulators used in chips. The problem chipmakers now face, as devices and their respective chip geometries shrink, is that electrons tend to skip from one copper wire to the next, because they are so close together, causing electrical current leakage. This causes the computer to suffer from reduced reliability and performance.
To avert this leakage, chip makers use a layer of tantalum nitrade to stick the copper to the silicon. But because these materials tend to mix together, an additional layer is needed to bind them, which, at about 10 to 15 nanometres, takes up valuable chip real estate.
This is where the Ramathan's nanolayer bonding comes into play. Because the nanoglue forms such a strong bond and also prevents the copper and silica from mixing, the use of tantalum can be eliminated from the equation, effectively shrinking the space between the two materials from about 15 nanometres to one nanometre.
"Nanolayers have properties that obviate all these problems: they can coat surfaces of any shape (they assemble by themselves due to chemistry), they inhibit atomic intermixing, they enhance adhesion and now they can produce remarkable adhesion values upon heating to temperatures previously not anticipated," said Ramanath.
Another bonus for chip makers is that the nanoglue can be made from inexpensive, commercially available products. Ramanath said it's possible to produce the nanoglue for as little as US$35 per 100 grams.
Ramanath and his team have filed a disclosure on their findings and are moving forward towards a patent. The team is also exploring what happens when certain variables of the nanoglue are tweaked, such as making taller nanolayers or sandwiching the layers between substances other than copper and silica.