Sensing Skin’s Saturation Level

When people talk about organs the instant thoughts probably go to the heart, liver, stomach and kidneys. The liver is the largest of these internal organs but when it comes to largest organ overall it us outstripped by the skin which is often not thought of as an organ but does contribute to about 15% of a human’s body weight. The skin is, like almost everything else in the human body, made of a lot of water. 64% of the skin is in fact made of water.

This is because one of the main purposes of the skin is to keep the large quantity of water in the the body, in the body. The epidermis is made of a series of keratinised cells held in a lipid which can allow water to either easily diffuse through the skin or bond to water molecules and hold them in suspension when necessary. If these processes fail and the skin does not get hydrated properly the most common sign is eczema but other dermatological problems can also arise. A frequently used tool for making measurements of skin hydration is the corneometer which uses a series of concentric ring electrodes to measure the capacitance of the skin to calculate the amount of water.

The problem is that to apply the electrodes to the skin requires pressure so that the connection is good. This force deforms the skin and so unsurprisingly can then affect the water near the skins surface changing the measured capacitance. Repeatability of these measurements is often difficult as a result. Recently there has been the development of sensing technologies for the thermal and electrical properties of the skin. Rather than hard electrodes that require brutish physical pressure the new materials and concepts lead to sensors that simply require Van der Waals forces to adhere rather than pressure so would be described as “soft” options. These sensors would not be detected even by the human touch and so could easily be applied to any part of the body even where the original pressure based technique would lead to discomfort. Tests on 20 patients have brought back promising results when it comes to the accuracy of these epidermal electronics and so hopefully technology like this could be used in the future for both in hospital and domestic monitoring of many aspects of a persons skin.

Paper links: Multimodal epidermal devices for hydration monitoring


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