Pressure ulcers (PUs) are injuries of the skin and underlying tissues resulting from prolonged applied pressure. PUs affect 2.5 million patients per year in the US, can develop in four to six hours and range from $2,000 to $70,000 to treat. They affect patients immobilized due to injury, illness, or sedation, patients with decreased sensitivity, commonly due to diabetes or spinal cord injury, or patients using prosthetics. Oklahoma is one of the US states with the highest number of patients suffering from PUs. In addition, Oklahoma ranks third in the country for diabetes-related deaths. Native Americans are twice as likely to have diabetes and, hence, develop the associated complications, including PUs. Finally, military personnel subject to long aeromedical evacuation are particularly vulnerable to PUs. Because PUs affect a large population, their treatment constitutes a tremendous financial burden on the healthcare system, up to $11 billion.
PUs develop under a combination of pressure and shear mechanical loading. To reduce the peak pressure applied on the skin in contact with the support, the pressure is distributed over a larger area. However, this simple mechanical principle is a challenge to implement on human bodies exhibiting a range of shapes and soft tissue properties.
In this study, we propose to develop a smart skin to treat and prevent PUs. The smart skin will act as an adaptive pressure off-loading device by continuously and autonomously redistributing the skin contact pressure. This goal will be achieved by harvesting the unique mechanical properties of liquid crystal elastomers. Pressure triggers a reorientation of their microstructure, which, in turn, leads to a change in shape and in mechanical properties. We will first quantify this change according to pressure levels relevant to PU located on the heel, leading to a model of the mechanical response of the smart skin to local pressure through time. We will then computationally determine the skin contact pressure between subject skins and smart skin from a pressure map measured underneath the smart skin. Finally, the smart skin will be tested on human subjects in quiet lying positions.