Fig 1.
The proposed solution of a non-absorbent, non-occlusive lubricant film at the PPE-skin interface, resulting in a lower risk of damage when wearing PPE for extended periods of time.
A: Schematic overview of the three main layers of human skin. B: The clinical problem of skin injury occurs because of elevated mechanical shear stresses acting on the skin. C: Skin lubrication leads to reduced friction and lower mechanical stress in the skin.
Fig 2.
Schematic overview of the measurement protocol.
A: Schematic of the interior of the tribometer setup. B: Schematic illustration of the measurement, adapted from Veijgen.16 C: Two typical friction measurements. D: Final processed data.
Fig 3.
Overview of results.
Table 1.
Summary of all lubricating agents tested.
Fig 4.
Mechanisms involved in lubricating the skin.
A: In the unlubricated situation the friction mainly arises mainly from lipids on the skin surface. The exact value varies strongly between people, but in general the coefficient of friction is close to 1. B: Lubricants are highly effective at reducing the shear strength of the interface, resulting in much reduced friction. C: If the lubricating substance occludes the skin, transepidermal water loss is prevented. This hydrates the epidermis from the inside, reducing the stiffness and increasing the contact area thus increasing the coefficient of friction. D: The lubricant may not persist due to absorption, evaporation and/or wear. Lubricant absorbed into the stratum corneum still affects swelling and stiffness, causing the friction to increase. E: The lubricant may absorb into the skin, swelling and plasticising the stratum corneum (SC). This will reduce the stiffness and increase the contact area. The coefficient of friction will increase with time. F: Particulates may reduce the coefficient of friction: a lamellar structure provides low shear strength whilst round particles act as rollers. Some particles absorb moisture, increasing the stiffness of the stratum corneum. The combination of these effects may lead to a strong reduction of the coefficient of friction.
Fig 5.
Examples of various observed friction traces.
A: Friction trace observed for a moisturiser upon application and after 10 minutes: high static friction due to absorption into the skin. B: Friction trace for petrolatum+lanolin 2h after application, followed by removal using an alcohol wipe and a 5-minute wait, indicating occlusion. C: Friction trace before applying and after removal of wax, indicating the friction returns to the initial state and no occlusion occurs.