Single-molecule nanocar developed by the joint collaboration of Rice University and North Carolina State University researchers was finally tested in open air instead of the usual vacuum.

Testing in open air, the researchers have found that these hydrophobic nanocars get stuck and form huge speed bumps, making the "road" unsafe for them.

The research and development is in preparation for the first NanoCar Race in Toulouse, France this coming October. They will join four other international teams in the competition.

Although the race would be in an ultra-cold vacuum environment, the researchers tested the nanocars in a natural setting because they wanted to know the conditions that would affect the movement of the car while in the macro world.

"Our long-term goal is to make nanomachines that operate in ambient environments. That's when they will show potential to become useful tools for medicine and bottom-up manufacturing," said James Tour, a chemist from the Rice University who was among those who conducted the test.

Nanocar Hydrophobicity

The nanocars were built with adamantane wheels, which are naturally water-repellant or hydrophobic because that's the only way for them to stay attached to the surface. This becomes the downside because when there is increased hydrophobicity, the materials are more likely to stick to each other. This reduces the surface area exposed to the water, thus immobilizing the cars. This is in stark contrast with hydrophilic materials that can freely hang in the water.

In the research, the nanocars where placed either on a clean glass substrate or on a polymer polyethylene glycol (PEG)-coated glass. The PEG-coated slides were primarily used for their non-sticky and anti-fouling properties. The clean glass was treated with hydrogen peroxide to prevent the adamantane wheels from sticking together.

Directed diffusion during the tests prevented the car to be driven, but Tour said that was not the main goal of the test drive. The test in the natural setting was carried out to know the kinetics involved in nanocar movement and analyze the surface and vehicle's potential energy interaction. Tour said that it is about finding out the factors that would force the nanocar to stop and the amount of external energy needed to make it move again.

During the test, the cars were observed for 24 hours using embedded fluorescent tags. Researchers noted that there was a gradual decrease in the movement of the car via the Brownian diffusion. Tour explained that this could be due to the slides' absorption of the air molecules that caused the slides to become "dirty."

Since the nanocar is made up of a single and complex molecule, any amount of molecule in its way would serve as an obstacle. As it bumps the obstacles, the car slows down and would eventually stop over time.

The test drive showed that the cars that move on the PEG-coated glass were twice than those in the clean glass. It was also noted that the rate of movement of all cars in the PEG-coated glass was higher.

The researchers used confocal microscopes to monitor the cars instead of scanning tunneling microscopes because the energy emitted by the scanning microscopes affect the car's movements.

Tech Times earlier reported about Penn State researchers' discovery of a silicon non-stick surface that functions better than nature-inspired counterparts.

The study is published online in the American Chemical Society journal, Journal of Physical Chemistry C, on April 29.