Lin Y.-CCai M.-XYang Y.-J.YAO-JOE YANG2021-08-052021-08-0520219601317https://www.scopus.com/inward/record.uri?eid=2-s2.0-85103587554&doi=10.1088%2f1361-6439%2fabea04&partnerID=40&md5=0d70b445765064a996f1392dd17dbe22https://scholars.lib.ntu.edu.tw/handle/123456789/576223This paper presents a novel LC-based passive wireless flexible pressure sensor that employs microstructured ferromagnetic films with tunable effective permeability. The proposed device consists of a micromachined planar spiral coil and a polymer film with cilia arrays (CAs) realized by the ferrofluidic instability principle. The effective permeability of the polymer film can be tuned by deforming the CAs with externally applied pressure, which can be estimated in turn by detecting the resonant frequency of the device using the phase-dip technique. The fabrication parameters for synthesizing different dimensions and densities of CAs were investigated as well. Devices of different CA densities were measured and discussed. The measured results showed that the device quality factor and phase change both increased with applied pressure. Due to this characteristic, the proposed device is advantageous over typical capacitive LC-based devices and performs better in wireless interrogation while maintaining the sensitivity of pressure sensing. ? 2021 IOP Publishing Ltd.Critical currents; Ferromagnetism; Mechanical permeability; Microstructure; Natural frequencies; Polymer films; Pressure sensors; Semiconducting films; Applied pressure; Device quality factor; Effective permeability; Fabrication parameters; Ferromagnetic films; Flexible pressure sensors; Passive pressure sensors; Wireless interrogations; Ferromagnetic materials[SDGs]SDG7journal article10.1088/1361-6439/abea042-s2.0-85103587554