Today, sensors, transducers, and actuators have found several applications in various fields including, engineering, artificial intelligence as well as in medicine. In medicine, for example, they have been used to monitor and detect various body functions and organs such as the changes and variations in the blood flow, which can be detected and recorded by capacitive sensors.
In a bid to address the various health challenges that affect most of the astronauts during their space missions, the potential solution is seen in using wearable sensors and actuators. The human venous system, for instance, is profoundly affected by the absence of gravity especially for astronauts undertaking long-term space missions.
Although various systems have been developed for use in microgravity environmental conditions, they have still experienced challenges here and there. They have not for instance given an in-depth understanding of the physiology of venous return mechanism which may help on preventing the astronauts from he effects of the fluid shifts to the upper body parts from the lower body parts, such as hypovolemia,drainage visual impairment, chronic fatigue among others.
University of Ferrara researchers Professor Angelo Taibi and colleagues, developed a new system that can be effectively used in the microgravitational conditions for aerospace missions, by detecting the variations in the venous blood volume of the human. The plethysmography systems supports inflight operations as well as baseline data collections. Their research work is currently published in the journal, Sensors and Actuators A: Physical.
The system developed by the research team consisted of solid-state strain-gauges of different lengths, signal acquisition and storage circuit in integrated within a well-designed enclosure for safety purposes. The system also uses capacitive sensors based on the principle that the capacitance of the sensors is directly dependent on the stretching magnitude. The capacitive sensors are connected electrically to the portable electronic unit, where changes in the volume of blood are recorded overtime after their measurements from the designated body parts.
From the experiments performed in the microgravity conditions, the authors observed that the system was sensitive enough to accurately detect the blood variations in the neck veins, and other body parts. The sensors also produced capacitance values that were proportional to their respective lengths, with precision of the electronic device within 1 %.
“The success of the experiment, funded by the Italian Space Agency (ASI), has demonstrated that thanks to its easy portability, non-invasiveness, and non-operator dependence, the plethysmography system can be considered as a novel tool for use aboard the ISS. Further trials are now under way to complete the investigation on the drainage function of the neck veins in microgravity.” said Dr. Angelo Taibi, first author on the paper.
The system does not require complicated calculations because the sensor elongation could easily be detected through measurements of the time taken by its capacitance to charge. The strain-gauges devices made this possible as they were supplied by a constant current. As a result, detection of the variations in the cross-sectional areas in the neck was achieved. Due to its sensitivity, the plethysmography system provides accurate data that can further be used for other studies such as those concerning cardiac oscillations. The study will, therefore, advance the operations in microgravity environments, for example by ensuring safety for the astronauts during their space missions.
Taibi, A., Andreotti, M., Cibinetto, G., Cotta Ramusino, A., Gadda, G., & Malaguti, R. et al. (2018) Development of a plethysmography system for use under microgravity conditions. Sensors and Actuators A: Physical, 269, 249-257.Go To Sensors and Actuators A: Physical