The purpose of this study is to design a non-contact capacitive sensor. It will not cause the patient's discomfort due to traditional electrode adhesive, and thus enhance the quality of medical care. The structure of the electrode is concentrical foil on one side and the other surface is the detection circuit which can convert physiological signals. The study purposed the simulation way to confirm the capability of the non-contact capacitive sensor. Two copper plates embedded into two sides of a piece of pork are connected the physiological simulation signal. Then the propsed capacitance electrode measured this signal on the pork separated by the cotton. This study exhibited the way can detect clearly the simulation signals form the phantom.

THE STUDY OF NON-CONTACT SENSOR EXPERIMENT ON PHANTOM

The electrode is made of FR4 board. Its one side surface is concentric foil close to the cotton, and the other side is detection circuit. The radius of the outer ring foil is 20 mm, and the radius of inner circle foil is 9.5 mm. The gap between these two foils is 3 mm (Figure 1). The two foils are respectively connected to the amplifier circuit of Sc shown in Figure 2. Two copper plates embedded into two sides of a piece of pork are connected the physiological simulation signal which is 1 Hz square wave (Figure 3). Then the proposed capacitance electrode measured this signal on the pork separated by cotton shown in Figure 4. Moreover, Vcsupplies 500 Hz sine wave for carrier wave.

Figure 1. The electrode.

When the electric field of simulation signals (square wave) which are 10 mVpp, 100 mVpp, 500 mVpp, 1 V are applied into the pork respectively, the signals measured from the proposed capacitance electrode separated by cotton are shown in Figure 5 respectively. Notice that these signals has been filtered out the 500 Hz carrier wave. it is very clear that the proposed sensor can take out the similar signals from physiological tissue by noncontact method. And the applied voltage does not affect the sensitivity of the output value.

This study proposed an innovative sensor. This sensor is placed on the surface of cotton cloth, and human body electrical signals can be measured. It improves the inconvenience of traditional adhesive electrodes to the patients and increases health human resources. During this study, we figure out that the signal measured by non-contact sensor is easily affected by the electrostatic effect, adhesiveness, and the position of measurement. Overall, the study of non-contact capacitive sensor is able to measure the potential signals of organism and the applied voltage does not affect the sensitivity of the output value.

[1] Y. B. Jing Zhang, D. Shen, L. Wen, C. Ding, Z. Cui, F. Tian, B. Yu, B. Dai, and J. Zhang, “A portable ECG and blood pressure telemonitoring system,” IEEE Engineering in Medicine and Biology Magazine, vol. 18, no. 4, pp. 63-70, 1999.

[2] Akinori Ueno, Yasunao Akabane, Tsuyoshi Kato, Hiroshi Hoshino, Sachiyo Kataoka, and Yoji Ishiyama, “Capacitive Sensing of Electrocardiographic Potential Through Cloth From the Dorsal Surface of the Body in a Supine Position: A Preliminary Study,” IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 54, NO. 4, APRIL 2007.

Hung-Chi Yang*, Tsung-Fu Chien, Rui-An Chang, Yu-Ming Chen

Department of Electrical Engineering, Southern Taiwan University, Tainan, TAIWANE-mail: hugiyang@mail.stut.edu.tw

2012 INTERNATIONAL SYMPOSIUM ON NANO SCIENCE AND TECHNOLOGYTainan, TAIWAN, 8-9 November 2012

Figure 2. Detection circuit.

Abstract

Experimental

Results and Discussion

Conclusion

References

Figure 4. Electrode measurement location.Figure 5. the signals measured by the proposed sensor, as simulation signals (square wave) in pork is

(a)10 mVpp, (b)100 mVpp, (c)500 mVpp, (d)1 Vpp.

(a) (b)

(c) (d)

Figure 3. Pork Size.