What instrumented friction tells you
Friction controls how a medical device slides through tissue, how a coating feels and wears, how a film or label handles, and whether a micro-mechanism moves smoothly. Many of these contacts carry only milli-newtons of load. Instrumented friction testing measures the coefficient of friction at those loads, on the same instrument that measures hardness, modulus and scratch resistance.
How the test works
- The counterbody, a ball, stylus or custom tip, is brought into contact with the sample.
- A constant normal load is applied and held by closed-loop control.
- The sample moves under the counterbody at a set speed and distance, while the friction force is recorded continuously.
- The coefficient of friction is calculated along the path; repeats and different conditions (dry, liquid, humid, hot or cold) are compared.
Low load, real conditions
At low load, accurate force control matters more than raw capacity. In NANOVEA’s pacing lead study, the nano module held 50 mN constant while a 6 mm steel ball slid 10 mm at 20 mm/min over silicone and polyether-polyurethane lead insulation, both dry and in Hanks’ solution. That is the kind of contact the leads see in the body, which a tribometer at higher load could not reproduce.
Friction as a diagnostic in scratch testing
Friction is also recorded in every scratch test. As load increases, friction typically rises steadily, then changes abruptly when the stylus breaks through a coating. In NANOVEA’s TiN study, friction climbed to about 0.3 before the first chipping at about 3.3 N. Combined with depth and acoustic emission, the friction record helps locate failure precisely.
When to use a tribometer instead
For higher loads, long sliding distances, wear rate measurement and standard friction-and-wear methods such as ASTM G99 and G133, NANOVEA tribometers are the right platform. The mechanical tester covers the low-load end of the same range.
