Design and development of an active Laplacian sensor for non-invasive recordings of the intestinal bioelectrical signal

Abdominal surface recordings of the electroenterogram (EEnG) could be a noninvasive solution to study the intestinal motility. However, surface EEnG is a weak signal (muV) sensitive to physiological interferences such as ECG and respiration. The goal of this work has been to develop a modular Laplacian sensor to enhance the quality of conventional bipolar recordings. This sensor is made up by two parts: the passive part which consist of 3 concentric Ag/AgCl ring electrodes; and the active part which is a battery-powered signal conditioning circuit. Each part is etched in a different printed circuit board (PCB), and they are connected to each other by SMT connectors. So that, the sensing part can be treated independently for its maintenance and replacement, while the active part can be reused. In a preliminary recording session, the slow wave (SW) component of the EEnG was identified in the signal provided by the Laplacian sensor. Moreover, this signal proved to be less affected by respiration and ECG interference.