Inductively coupled microfluidic pressure meter forin vivomonitoring of cerebrospinal fluid shunt function

A microfluidic pressure sensor with inductively coupled, wireless readout capability has been developed for integration into cerebrospinal fluid shunt valve implants. The sensor consists of a deformable PDMS film that is bonded over a microfluidic reservoir, forming a fluidic capacitor. Deflection of the capacitor membrane is detected remotely through a shift in the resonance frequency of a micro-fabricated LC circuit. Sensors were fabricated by a combination of conventional MEMS technologies and rapid soft lithography. A direct pattern transfer technique was used to pattern the deformable PDMS film with a metal coating for the capacitive readout. The mechanical response of the fluidic capacitor was characterized by measuring the deflection of the PDMS film using an extrinsic Fabry-Perot interferometer (EFPI), and wireless sensing was demonstrated by the shift in resonance frequency of the sensor via an inductively coupled antenna. The sensor transduces pressure into a change in resonant frequency with sensitivity >?3.4?ppm Pa?1 and responsivity 4.6?kHz Pa?1, over a dynamic range of 0 ~ 3 kPa.Keywords CSF shunt, Microfluidic pressure meter, Inductively coupled antenna, Fluidic capacitor, Implantable flowmeter