A thin-film aluminum strain gauges array in a flexible gastrointestinal catheter for pressure measurements

This paper presents an innovative approach to measure the pressure patterns associated with the motility and peristaltic movements in the upper gastrointestinal tract. This approach is based on inexpensive and easy to fabricate thin-film aluminum strain gauge pressure sensors using a flexible polyimide film (Kapton) as substrate and SU-8 structural support. These sensors are fabricated using well-established and standard photolithographic and wet etching techniques. Each sensor has a 3.4 mm2area, allowing a fabrication process with a high level of sensors integration (four sensors in 1.7 cm), which is suitable for placing them in a single catheter. These strain gauges bend when pressure is applied and, consequently, their electrical resistance is changed. The fabricated sensors feature an almost linear response (R2= 0.9945) and an overall sensitivity of 6.4 mV mmHg-1. Their readout and control electronics were developed in a flexible Kapton ribbon cable and, together with the sensors, bonded and wrapped around a catheter-like structure. The sequential acquisition of the different signals is carried by a microcontroller with a 10 bit ADC at a sample rate of 250 Hz per-1sensor. The signals are presented in a user friendly interface developed using the integrated development environment software, QtCreator IDE, for better visualization by physicians.This work has been funded by FEDER funds through the Eixo I do Programa Operacional Fatores de Competitividade (POFC) QREN, project reference COMPETE: FCOMP-01-0124FEDER-020241, and by FCT — Fundação para a Ciência e a Tecnologia, project reference PTDC/EBB-EBI/120334/2010, and project reference UID/EEA/04436/2013, and by FEDER funds through the COMPETE 2020 — Programa Operacional Competitividade e Internacionalização (POCI) with the reference project POCI-01-0145-FEDER-006941. P J Sousa thanks the FCT for the SFRH/BD/81562/2011 PhD grant. V C Pinto thanks the FCT for the SFRH/BD/81526/2011 PhD grant