Design and Fabrication of a pH Sensor-Coated Microreactor System

This study utilizes additive manufacturing to fabricate a transparent microreactor with customizable internal structures, integrating optical sensors for pH detection. A sol-gel method was employed to prepare the pH sensor film, using tetraethoxysilane (TEOS) and phenyltrimethoxysilane (PTMS) as precursors and methyl red (MR) as a pH indicator. The real-time response of the pH sensor film within the microreactor channels was assessed. The fabricated sensor films underwent initial functionality testing on 3-D printed substrates. Subsequently, these sensor films were applied to the microreactor channels. pH testing within the microreactor channels was executed by alternately exposing the system to acidic and basic solutions. Over a 5-min period, the sensor exhibited color changes corresponding to the pH values. A simple method of using handheld portable detector such as a smartphone camera with dedicated red, green, blue (RGB) software was used for comprehensive color analysis. The swelling test findings show the inclusion of sensor films demonstrates a mitigated degree of swelling in substrates, enhancing operational stability by safeguarding polyacrylate against deleterious swelling effects. The analysis of contact angles revealed that the pH sensor film amplifies hydrophobicity in contrast to the polyacrylate. The pH sensors demonstrate a broad dynamic range (pH 2–11) and high reversibility.