On the development of meta-structure-based conformal sensors for biomedical applications

Abstract

In the past decade, bio-sensors prepared by 3D printing have attracted significant attention from researchers due to their ability to precisely monitor the health of a patient remotely via a wireless device. Also, advancements in the field of sensors have been reported such as conformability, wireless transmission of data (in different bands), shape memory effect, etc. But hitherto little has been reported on the development of meta-structure-based conformal sensors in industrial scientific, and medical radio (ISM) band for biomedical applications. In this work, initially feedstock strands of polylactic acid (PLA) with reinforcements of hydroxyapatite (HAP) and chitosan (CS) were prepared using a twin-screw wire extruder (TSE), for 3D printing of the composite substrates (to be used as a dielectric material for sensor fabrication). The tensile specimens (of prepared PLA composite) were prepared based on the design of experiment (DOE), and different characterizations (i.e., mechanical, electrical, and morphological) of the composite material have been performed to check the suitability of the material for sensor development. Following that, the set of substrates of the sensors has been fabricated as per the DOE to ascertain the effect of different positions of meta-structures on the performance of the sensor. Further, the prepared set of sensors was tested on a vector network analyzer (VNA) and the response has been recorded in the form of insertion loss (S21) vs radiating frequency (fr) while providing the deformation longitudinally (at different deformations i.e., 0 cm, 0.5 cm, and 1 cm) to check the conformability of the sensor. Finally, based on the analysis of variance (ANOVA) the sensor at the best setting was designed and simulated in high-frequency structure simulator software (HFSS) to identify the radio-frequency (R-F) behavior of the sensor.