Nanomachines may one day climb along your skin, swim through your bloodstream, and fly through the air we breathe. While the hazards of such miniature machines make rich cautionary science fiction fodder, the benefits may also be great.
While there have been great advances in developing useful nanoparticles and tiny nanodevices, the research into controllable platforms to deliver these devices on lags behind. One such delivery platform is Rice University's nanocar. James Tour a Professor of Chemistry, mechanical engineering and materials science and computer science at Rice, created the nanocar in 2005 spawning much excitement and subsequent research.
The car was made primarily out of carbon and featured buckyball wheels. Later a paddlewheel motor powered by light was added, and the old wheels were swapped out for carboranes, which didn't trap the light energy like the buckyballs did. Rice has created a number of variants including nanotrucks, nanobackhoes and other models.
Now Rice has rolled out the new model of its nanocar with some attractive features. The original nanocars ran very hot -- requiring temps of 200 °C to travel across surfaces. The new car automatically travels across surfaces at room temperature.
The new work is possible thanks in part to an innovation in imaging which saw a switch from imaging the nanocar with a scanning tunneling microscope (STM) to single-molecule fluorescence imaging. The new imaging technique, unlike STM requires no conductive substrate to visualize the car. The improvement was cooked up by Rice associate professor Stephan Link.
The researchers discovered by accident that their new cars were running at room temperature. Describes Professor Link, "We thought, 'We're just going to take an image, and nothing's going to happen'. To my surprise, my students came back and said, 'They moved!'"
Using a new tracking algorithm with time-lapse photography, the team detected the cars, tiny fluorescent dots, zig-zagging over a glass surface at a rate of 4.1 nanometers (or two nanocar lengths) per second. Similar to techniques astronomers use to track moving stars, the new technique identified the nanocar by spotting its movement versus other fluorescing objects.
The new technique used tetramethylrhodamine isothiocyanate dye, which was also polarized, so you could tell which way the car was pointing. Currently the dye is dragged like a trailer, but Professor Link hopes to incorporate it into the frame to speed up the car and cut drag. He also hopes to add an extra pair of wheels to the current four to help the car maintain a straight path. He states, "Now that we see movement, the challenge is to take it to the next level and make it go from point A to point B. That's not going to be easy."
The new research is published in the journal ACS Nano.