An intelligent monitoring
lubricant is essential for the development
of smart machines because unexpected and fatal failures of critical
dynamic components in the machines happen every day, threatening the
life and health of humans. Inspired by the triboelectric nanogenerators
(TENGs) work on water, we present a feasible way to prepare a self-powered
triboelectric sensor for real-time monitoring of lubricating oils
via
the contact electrification process of oil–solid
contact (O–S TENG). Typical intruding contaminants in pure
base oils can be successfully monitored. The O–S TENG has very
good sensitivity, which even can respectively detect at least 1 mg
mL
–1
debris and 0.01 wt % water contaminants. Furthermore,
the real-time monitoring of formulated engine lubricating oil in a
real engine oil tank is achieved. Our results show that electron transfer
is possible from an oil to solid surface during contact electrification.
The electrical output characteristic depends on the screen effect
from such as wear debris, deposited carbons, and age-induced organic
molecules in oils. Previous work only qualitatively identified that
the output ability of liquid can be improved by leaving less liquid
adsorbed on the TENG surface, but the adsorption mass and adsorption
speed of liquid and its consequences for the output performance were
not studied. We quantitatively study the internal relationship between
output ability and adsorbing behavior of lubricating oils by quartz
crystal microbalance with dissipation (QCM-D) for liquid–solid
contact interfaces. This study provides a real-time, online, self-powered
strategy for intelligent diagnosis of lubricating oils.