The design of a wireless flexible capacitive sensor detection system to detect liquid level in plastic bag intravenous drip sets

Purpose: Intravenous (IV) therapy is extensively used in hospital treatments for infusion of liquid substances directly into a vein. When the medicine has been fully dispensed, an air embolism can be occurred since air in the IV drip bag could enter into the patient's vein, which is hazardous to the patient's safety. To prevent this situation, in this paper, design of a wireless detection system using flexible capacitive sensor to detect liquid level of IV drip set is proposed. Methods: In the conducted research, a simulation model of capacitive sensor technology was shown by using finite elements analysis (FEA), and its proper geometrical dimension of the capacitive sensor was found out. The studied capacitive sensor was used in this proposed wireless detection system. The system consisted of a wireless capacitance detector for liquid level detection, and a wireless receiver for acquiring the measuring data in another place. The flexible capacitive sensor was fixed on one side of the wireless capacitance detector, and the wireless capacitance detector was placed at the bottom surface of the plastic IV drip bag to measure the changing level of the capacitance. The measured signal from flexible capacitive sensor was converted into digital data by a relaxation oscillator circuit. In addition, a 2.4 GHz wireless communication method was used in this system for wireless data transmission. Results: The proposed flexible capacitive sensor was shown a good performance in the basic experiment of liquid level detection in the plastic IV drip bag, and the wireless detector is able to send the measured data to the receiver in other place by the wireless method. The PC which connected with wireless receiver can give an alarm immediately, when the liquid in the plastic IV drip bag is almost used out. Conclusions: The proposed flexible capacitive sensor is able to attach on the plastic IV drip bag completely, and the experiment data shows that the proposed wireless flexible capacitive sensor detection system is possible to detect the liquid level of the plastic IV drip bag. But in the future, further research is needed.