A newly developed micro-sensor can detect dehydration, and can alert the user. In particular, this aid can be extremely useful in the care of the elderly. The new sensor is only 16 millimeters in diameter and 8 millimeters high, but contains everything needed to measure fluid balance in the body according to Dr. Luis André L. Fernandes of the Faculty of Technology, Natural Sciences and Maritime Sciences who defended his doctoral dissertation “The development of a miniaturized hydration sensor based on the principle of osmotic pressure” on Friday 27 January at University College of Southeast Norway (USN). 
“Life originated in the sea, and the salt concentration in the body is a legacy from the time humans lived in the sea. Most of us are a little dehydrated all the time, and coffee promotes the dehydration. Therefore, you should always carry a glass of water and drink a little all the time.”, says Professor Erik Andrew Johannessen at the Department of Microsystems at USN. He has been one of the supervisors for Luis André L. Fernandes.
According to the researcher, the sensor contains a fluid filled pressure chamber with a constant salt concentration, which communicates with the water and salt on the outside through a membrane. When we lose fluid, water disappears while the salts remain. This leads to an increase in the salt concentration on the outside. This then starts a process to draw water out of the pressure chamber on the sensor.
This process is known as osmosis. This results in a pressure drop inside the sensor, which can be reconciled with the salt concentration outside the sensor. The opposite happens when we drink liquid. The salt concentration on the outside of the sensor falls, and the salt inside the pressure chamber ensures that the water flows again and the pressure increases.
This chemical process creates pressure inside the sensor, and this pressure is a direct result of the fluid balance in the body.
“This is one of several examples of technologies that can be important for the elderly living at home. Different types of sensors can help alert when people are not in shape. The challenge is that it can be a complicated road ahead until this technology can be used on humans. There are numerous tests and approvals that must be in place before we get that far”, says Professor Yngvar Berg, director of the Institute for microsystems at USN.
The doctoral work has taken place at the Department of Microsystems at USN and the Department of Informatics at the University of Oslo.
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