Navigation Links
'Heftier' atoms reduce friction at the nanoscale, study led by Penn researcher reveals
Date:11/1/2007

PHILADELPHIA - A research team led by a University of Pennsylvania mechanical engineer has discovered that friction between two sliding bodies can be reduced at the molecular, or nanoscale, level by changing the mass of the atoms at the surface. Heavier atoms vibrate at a lower frequency, reducing energy lost during sliding.

The study appears in the November issue of the journal Science.

Penn researchers, along with colleagues at the University of Houston and the University of Wisconsin now at IBMs Zurich Research Laboratory and the Argonne National Laboratory, used atomic force microscopy like an old-fashioned record needle, sliding it along single-crystal diamond and silicon surfaces to measure the force of friction. Before doing so, researchers coated each crystal surface with one of two adsorbates designed to best exhibit variations in the mass of the atoms at the surface without changing the chemistry. The first adsorbate was a single layer of hydrogen atoms. The second was its chemically similar but heavier cousin, deuterium, a hydrogen atom with a neutron stuffed inside its nucleus.

Our study found that the larger mass of the terminating atoms at the surface, in this case deuterium, led to less energy lost to heat in the system, Robert Carpick, associate professor of mechanical engineering and applied mechanics at Penn, said. The larger atomic mass of deuterium results in a lower natural vibration frequency of the atoms. These atoms collide less frequently with the tip sliding over it, and thus energy is more slowly dissipated away from the contact.

The single layer of atoms at the surface of each crystal acts as an energy transfer medium, absorbing kinetic energy from the tip of the atomic force microscope. The tips were less than 50nm in radius at their ends. How much energy is absorbed is dependent, researchers found, on the adsorbates natural atomic vibration frequencies. The heavier an atom, the lower its vibrational frequency. The lighter an atom, the faster the vibrations and thus the faster the dissipation of energy from the contact in the sample. Keeping the atoms chemically similar avoided any changes arising from chemical bonding.

The Penn findings provide a better understanding of the nature of friction, which lacks a comprehensive model at the fundamental level.

We know how some properties -- adhesion, roughness and material stiffness for example -- contribute to friction over several length scales, but this work reveals how truly atomic-scale phenomena can and do play a meaningful role, Matthew Brukman, a contributor to the research, said.

Industry has long been concerned with ways to reduce friction between objects, both to maintain the energy of the system as well as to reduce heat-generation and wear, which can weaken machinery and materials to the breaking point. The authors note that improved friction models can be used for the opposite effect; makers of some mechanical components such as automobile clutches may be interested in techniques to increase friction without changing the wear or adhesion of materials.

Even in the absence of rough edges or wear between sliding bodies, friction between the atoms at the surface causes vibrations which dissipate energy, but the exact mechanisms of this process remain unresolved. Scientists continue to explore the details of friction, and other open questions include the effects of environmental variables such as temperature and atmosphere.


'/>"/>

Contact: Jordan Reese
jreese@upenn.edu
215-573-6604
University of Pennsylvania
Source:Eurekalert

Related biology news :

1. Male circumcision reduces risk of HIV transmission from women to men
2. Deficiency of growth hormone and IGF-1 reduces cancer and kidney disease, but creates other problems
3. Use of PET can reduce, may eliminate more strenuous drug development trials with animals
4. Solutions that reduce death of marine life reeled in by International Smart Gear Competition
5. Physiological effects of reduced gravity on bacteria
6. New strategies to reduce hospital-aquired infections
7. New miniaturised chip dramatically reduces time taken for DNA analysis
8. Scalpel-free surgery could reduce risk of HIV and hepatitis exposure for health care workers
9. Newly recognized gene mutation may reduce seeds, resurrect plants
10. New processing method reduces peanut allergenicity
11. Blocking the nerve receptor EP1 in mouse models reduces brain damage caused by stroke
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:2/8/2016)... 2016 Worldcore is ... innovation for clients, comfort and unbeatable security, with ... --> Worldcore is the first EU-regulated ... comfort and unbeatable security, with a Voice Biometrics ... Worldcore is the first EU-regulated global payment ...
(Date:2/4/2016)... -- The field of Human Microbiome research and ... hubs of the biotechnology industry. While the Human ... human microbiota, have garnered a lot of attention ... has literally exploded in terms of both basic ... on biomedical aspects of research, development, and commercial ...
(Date:2/3/2016)... February 3, 2016 --> ... research report "Automated Fingerprint Identification System Market by Component ... Application (Banking & Finance, Government, Healthcare, and Transportation) and ... the market is expected to be worth USD 8.49 ... between 2015 and 2020. The transformation and technology evolution ...
Breaking Biology News(10 mins):
(Date:2/10/2016)... 10, 2016 Early-career researchers from ... Peru , Uganda and Yemen ... health and nutrition   Indonesia , ... and Yemen are being honored for their ... are also celebrated for mentoring young women scientists who are pursuing careers ...
(Date:2/10/2016)... -- ASAE is introducing a hybrid membership model which ... option of joining or renewing through an organizational purchasing ... size, every employee in any size association or AMC ... available member benefits.   John H. Graham, ... will allow organizations of any size and their employees ...
(Date:2/10/2016)...  Allergan plc (NYSE: AGN ) a leading ... , Allergan,s CEO and President, will be featured as ... the RBC Capital Markets Healthcare Conference on Tuesday, February ... York Palace Hotel in New York, NY ... can be accessed on Allergan,s Investor Relations web site ...
(Date:2/10/2016)... ... 10, 2016 , ... HOLLOWAY AMERICA, a leading custom stainless ... Mountain Chapter 21st Annual Vendor Exhibition on Thursday, February 18, 2016. The Rocky ... its annual event, which will run from 3:00 p.m. - 8:30 p.m. at ...
Breaking Biology Technology: