Inductively coupled microfluidic pressure meter for in vivo monitoring of cerebrospinal fluid shunt function

Abstract

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

Acknowledgements

This work was funded in part by the Biomedical Innovation Fund which is sponsored by the University of Virginia’s Department of Biomedical Engineering and the Ivy Foundation, as well as by the National Institute of Health (NIBIB) through grant number 5R01EB011591 - 02.

Declaration of interest: Authors Gillies, Begley, Utz and Broaddus may receive royalties through licensing agreements for the intellectual properties associated with this technology, as negotiated by their institutions.