A simulated tip bearing a C60 flake being dragged over C60.A team of scientists from Italy has developed a new theoretical approach to using fullerene spheres to help reduce friction and thereby allow movement in possible future nano machines, devices built from individual atoms first popularized by K. Eric Drexler in the 1980s. Fullerenes, C60 molecules also known as buckyballs, were shown by computer simulation to slide on the nanoscale, and thus possibly act as “nano-bearings” to help the machines work more efficiently. The researchers hope to exploit phase transitions to directly actuate mechanical motion in such devices.
Existing friction control techniques at the nanoscale lack a dynamical way to control friction, and the possibility of tuning, flexibility and reversibility in the friction coefficient of two bodies while they are sliding, limiting the potential lifetime. The coefficient is dependent on material properties that include elasticity, heat conductivity and charging capability, as well as on interface properties such as surface roughness and adhesion. However, two previous studies have yielded conflicting results: one finding that, above a certain temperature, the material was made to slide over a substrate with no significant reduction in friction, while other showed the decrease to be in the order of 100%. This new study investigated the dichotomy.
As reported in the journal Nanoscale [Benassi, et al. Nanoscale (2014) DOI: 10.1039/C4NR04641B], the study simulated
A team of scientists from Italy has developed a new theoretical approach to using fullerene spheres to help reduce friction and thereby allow movement in possible future nano machines, devices built from individual atoms first popularized by K. Eric Drexler in the 1980s. Fullerenes, C60 molecules also known as buckyballs, were shown by computer simulation to slide on the nanoscale, and thus possibly act as “nano-bearings” to help the machines work more efficiently. The researchers hope to exploit phase transitions to directly actuate mechanical motion in such devices.
Existing friction control techniques at the nanoscale lack a dynamical way to control friction, and the possibility of tuning, flexibility and reversibility in the friction coefficient of two bodies while they are sliding, limiting the potential lifetime. The coefficient is dependent on material properties that include elasticity, heat conductivity and charging capability, as well as on interface properties such as surface roughness and adhesion. However, two previous studies have yielded conflicting results: one finding that, above a certain temperature, the material was made to slide over a substrate with no significant reduction in friction, while other showed the decrease to be in the order of 100%. This new study investigated the dichotomy.
As reported in the journal Nanoscale [Benassi, et al. Nanoscale (2014) DOI: 10.1039/C4NR04641B], the study simulated a tip bearing a C60 flake that was dragged over a surface also made of C60. It was found that when the flake was attached and unable to rotate, the friction did not decrease, despite the temperature being raise to over 260°K. When the flake was able to rotate, there was substantial decrease in friction, allowing the flake to move more smoothly. The team questioned if friction and dissipation could be influenced by the occurrence of phase transition in the sliding bodies. The phase transition was demonstrated to reduce friction by a small amount, and trigger a change in the commensurability of the contact between the sliding nano-object and the fullerite underneath with dramatic changes in friction and sliding properties.
As author Andrea Benassi pointed out, the idea of “exploiting phase transitions can be easily implemented into existing mechanical devices, growing small coating layers of the desired materials hosting a specific phase transition directly onto the mobile elements.” They now hope to test their work in real operating conditions by developing prototype devices that are controlled by the promotion/suppression of convenient phase transitions.
that was dragged over a surface also made of C60. It was found that when the flake was attached and unable to rotate, the friction did not decrease, despite the temperature being raise to over 260°K. When the flake was able to rotate, there was substantial decrease in friction, allowing the flake to move more smoothly. The team questioned if friction and dissipation could be influenced by the occurrence of phase transition in the sliding bodies. The phase transition was demonstrated to reduce friction by a small amount, and trigger a change in the commensurability of the contact between the sliding nano-object and the fullerite underneath with dramatic changes in friction and sliding properties.
As author Andrea Benassi pointed out, the idea of “exploiting phase transitions can be easily implemented into existing mechanical devices, growing small coating layers of the desired materials hosting a specific phase transition directly onto the mobile elements.” They now hope to test their work in real operating conditions by developing prototype devices that are controlled by the promotion/suppression of convenient phase transitions.