On 3D printed polyvinylidene fluoride composite-based diaphragmatic hernia sensors

Abstract

Diaphragmatic hernia (DH) recurrence is a commonly reported disorder among bovines. Recently, studies have been reported using wireless devices (like ultrasonic and radio-frequency (RF) based pressure sensors) to detect DH. But hitherto, little has been reported on using polyvinylidene fluoride (PVDF)-based sensors mounted on the diaphragm of bovine to detect the recurrence of the DH post-surgery. In this work, the PVDF-hydroxyapatite (HAP)- chitosan (CS) composite in the proportion of 90-8-2 (wt.%) was used as a substrate for sensor fabrication based on microstrip patch antenna (MPA). Based on the results, the parts of the sensor, that is, substrate, patch, and the ground plane, were designed in the high-frequency structural simulation (HFSS) software assigned with the material properties of PVDF-HAP-CS (as substrate) and 17-4 precipitated hardened (PH) stainless steel (SS) alloy (as patch or ground plane). Upon simulation, it was observed that some deviation in resonance frequency occurred with/ without the natural bovine diaphragm, which was verified based on experimental analysis. The parts were 3D printed for validation through material extrusion (MEX) and direct metal laser sintering (DMLS) processes. Upon testing using a vector network analyzer (VNA), it was observed that the sensor without the diaphragm resonated at 3036.57 MHz with a return loss (S11) of −12.81 dB, whereas the sensor with the diaphragm resonated at 2019.35 MHz with an S11 of −21.06 dB. This shift in frequency with/without the diaphragm is measurable in the industrial, scientific, and medical (ISM) frequency band on a Bluetooth device to detect the reoccurrence of DH.