Design of pH Measuring in Wireless Therapy Capsule Against Helicobacter Pylori Infections

Abstract

A wireless blue light therapy capsule against Helicobacter Pylori infections based on a pH sensor was addressed. A pH measuring circuit module and wireless communication module were designed to pre-process and transmit the pH signal. By measuring the pH value changes, the capsule can identify the locations and trace the pH of the gastrointestinal tract. A micro controller was designed to sample the pH signal and regulate the therapy parameters according the feedback information. Vitro experiments were conducted to show the performances of the pH sensing module. Introduction Helicobacter Pylori (H. pylori) colonizes the mucus layer of the human stomach which causes peptic ulcers and adenocarcinoma [1]. Recently, blue light is widely used in clinic to kill bacteria. It is reported that blue light exhibits bactericidal effects against cultured Helicobacter pylori (H. pylori) and many other microbial bacteria around the wavelength of 405nm [2-3]. Additional tests indicated that the largest reduction in bacterial load was in the antrum (>97%), followed by body (>95%) and fundus (>86%), with treatments by blue light at wavelength of 408nm [4, 5]. These results proved that blue light could be used to kill the H. pylori in clinic to against the H. pylori infections. Advancement in sensor technology and semiconductor technology has prompted highly integrated applications. Endoscopy capsule and physiological parameters detection capsule are just some representatives. As a typical micro medical device, the first endoscopy capsule named M2A provided a noninvasive detection method for digestive tract [6]. Different capsule devices have been designed to suit different purposes in clinical treatments such as non-invasive capsule for targeted drug delivery, capsule robot for local surgery, or monitoring capsule for physiological information collection [7-11]. Combined blue light killing H. pylori with capsule designing, we proposed a blue light therapy capsule based on a pH sensor to against Helicobacter Pylori infections in this study. And pH measurement is the key issue in this paper will be discussed. By measuring the pH value of gastrointestinal tract, it indicates the approximate location of the capsule when it moved along in the digestive tract. For further, the device can mark the places with abnormal pH value and adjust work parameters with feedback information. System Design System architecture. The inner architecture of the proposed capsule, shown in Figure 1. The pH measuring unit consists of a pH sensor and a measuring circuit to detect the pH value. The pH sensor measures the changes of voltage that reflects the changes of pH values. The measuring circuit amplifies the voltage signal from the pH sensor so that the MCU can acquire the analog voltage signal accurately. 4th International Conference on Machinery, Materials and Computing Technology (ICMMCT 2016) © 2016. The authors Published by Atlantis Press 580 pH Sensor Signal Filter Signal Processing MCU LEDs Driver L E D S Power Management DC-DC Cell Battery Wireless Communication Figure 1. Architecture inside the capsule pH Sensor. The pH values range from 1 to 7.5 for the whole digestive tract with a pH value about 7 in the esophagus, 1~4 for the gastric juice, and 6.6~7.5 for the intestinal juice [12]. Clearly, the sensor needs to cover the entire pH range with a resolution less than 2.6. For above considerations, antimony electrode is selected as the pH sensor whose detection range is from 1 to 9. The antimony electrode belongs to the class of oxidation-reduction solid electrode which has two electrodes, one for pH measurement and the other for reference. The change of voltage between the two electrodes is measured, and it scales linearly with the change in pH value at a fixed ambient temperature. The out voltage formula as follow: 0 2.303 (1) RT V V pH F   where V is measuring voltage, R for gas constant 8.314, T as target temperature (K), F for faraday constant 96500. According to the formula, measuring voltage increases with the increase of pH value when the temperature is stable.