On the design and fabrication of polyvinylidene fluoride-based sensors to detect recurrence of diaphragmatic hernia

Polyvinylidene fluoride (PVDF) bio-sensors have gained potential interest in remote health monitoring of patients using Internet of Things (IoT) technologies. But hitherto, limited studies have reported on the fabrication of PVDF-hydroxyapatite (HAP)-chitosan (CS) based sensors processed through two different processing routes from a process suitability viewpoint to determine the recurrence of diaphragmatic hernia (DH). The sensors fabricated in this study comprise three layers, that is, a substrate (dielectric material), a metallic patch, and a ground plane that works on the microstrip patch antenna (MPA). Two manufacturing approaches have been followed in this study for the fabrication of the dielectric substrate: material extrusion (MEX) and gel-casting. Primarily, PVDF (90%) -HAP (8%) -CS (2%) has been selected for the sample preparation, following that different characterizations have been performed on the chosen composition to ensure its suitability for sensor fabrication. The simulated results were extracted in the form of return loss (S11) versus radiating frequency (fr), specific absorption rate (SAR) field, electric (E), and magnetic (H) field variables. Following that, the substrates were fabricated through the MEX and gel-casting approach, and Cu tape was used to make the conducting parts of the sensor. The sensor's radio-frequency (RF) behaviour was tested on a vector network analyser (VNA) to obtain the output of S11 versus fr. The RF-characteristic of the sensors fabricated through MEX and gel-casting approaches represent that the sensors designed for dielectric constant (epsilon r) = 9.61 resonate at 2.72 GHz for MEX and 2.67 GHz for gel-casting while possessing the S11of -14.14 and -28.40 dB respectively.