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BACKGROUND: Friction and shear forces are critical factors in the formation of skin injuries such as blisters, abrasions and decubitus. To understand these forces better, an apparatus was constructed for in vivo studies based on DaVinci’s classic sliding sled experiments.
METHODS: The measurement device consists of a supportive structure that maintains a parallel path for a sliding sled connected to a motorized unit via a load cell. The motorized unit and load cell interface with a computer to control sled motion and receive real-time signals from the load cell. These load cell signals measure compression and tension forces that result from movement of the sled sliding across the skin. Three experiments were conducted to validate usefulness of the device in vivo and to understand the effect of barrier films on skin frictional forces.
RESULTS: Experiment #1 measured skin friction at four different hydration levels. The data clearly show sensitivity of the device to measuring changes in skin hydration. Experiment #2 measured triplicate skin friction measurements over two treated sites on a single subject two minutes after application of the barrier films; the device clearly differentiated between residual tackiness of the two films. Experiment #3 measured skin friction on the volar forearms of nine subjects before and two minutes after application of two barrier films. The mean (SD) coefficient of friction for barrier film B was 1062.1 (272) grams, which was 257% higher than barrier film A, 412.4 (98.5) grams (p<0.0001, paired T-test).
CONCLUSIONS: The sliding sled apparatus can be used to compare the effect of application of topically applied products on skin friction. The two barrier films tested produced significantly different skin friction measurements.