Achieving superlubricity by placing water on plant oil

Friction at interfaces is a cause of damage, deterioration, and energy loss in automobiles and industrial equipment, etc. Establishment of low-friction technology is an important R&D theme as it leads to drastic increases in energy utilization efficiency and as a result can be expected to effectively reduce CO₂ emissions. Large amounts of lubricating oil or expensive lubricants such as graphene have conventionally been used to obtain low-friction surfaces and in particular superlubric state with a friction coefficient of 0.01 or less. However, applicability is limited due to environmental and cost concerns. In addition, lubricating fluids with low environmental impact such as water and ethanol are attracting attention, and water-based lubricating fluids in particular are considered promising as these are abundant and low-cost resources. However, low viscosity makes it difficult to both retain the fluid at the interface and create a liquid film with sufficient thickness, so it has been a challenge to obtain stable low-friction properties with a small amount.

AIST researchers achieved superlubricated surface with a friction coefficient of 0.01 or less. The surface that retains multiple lubricating fluids was developed by spreading oleic acid, which is a component of plant oil, on a hydrophobic-oleophilic treated material surface and placing water on that oil surface.

Friction has conventionally been reduced by using large amounts of lubricating oil or expensive lubricants such as graphene. However, the developed technology can achieve superlubric state with only plant oil spread thinly over a hydrophobic-oleophilic treated material surface and a small amount of water. This technology achieves a superlubricated fluid surface that is low cost and has low environmental impact simply by adding water on a lubricating oil film at the contact sites of equipment that requires low friction. As such, application is expected to contribute to reduction of CO₂ emissions by reducing energy loss due to friction and promoting efficient use of energy in automobiles and industrial equipment, etc.

More information:
Kengo Manabe et al, Green Superlubricity Enabled by Only One Water Droplet on Plant Oil-Infused Surfaces, Langmuir (2021). DOI: 10.1021/acs.langmuir.1c02689

Provided by Advanced Industrial Science and Technology