Implantable micromechanical parylene-based pressure sensors for unpowered intraocular pressure sensing

Abstract

This paper presents the first implantable, unpowered, parylene-based microelectromechanical system (MEMS) pressure sensor for intraocular pressure (IOP) sensing. From in situ mechanical deformation of the compliant spiral-tube structures, this sensor registers pressure variations without electrical or powered signal transduction of any kind. Micromachined high-aspect-ratio polymeric hollow tubes with different geometric layouts are implemented to obtain high-sensitivity pressure responses. An integrated device packaging method has been developed toward enabling minimally invasive suture-less needle-based implantation of the device. Both in vitro and ex vivo device characterizations have successfully demonstrated mmHg resolution of the pressure responses. In vivo animal experiments have also been conducted to verify the biocompatibility and functionality of the implant fixation method inside the eye. Using the proposed implantation scheme, the pressure response of the implant can be directly observed from outside the eye under visible light, with the goal of realizing convenient, direct and faithful IOP monitoring in glaucoma patients.

A microscale optical implant for continuous in vivo monitoring of intraocular pressure

“…Such large implants have damaged surrounding 1 tissues and led to medical complications 66,67 . Previously investigated optical sensing approaches include a fiber-tip-based interferometry for hydrostatic pressure sensing [68][69][70][71][72][73][74] , a visualidentification-based method applied to pressure-sensitive microfluidic or micromechanical structures 75,76 , and laser-excited fluorescence measurements for ICP and IOP monitoring 77,78 . These approaches are promising, and with more improvements in terms of miniaturization and readout techniques, they may become practical approaches for IOP monitoring.…”

Pressure sensor based on flexible photonic crystal membrane

“…Furthermore, they are not transparent and need to be placed far enough outside of the optical axis to not impair the patient. Other implantable devices without power supply have been suggested for camera read out [3,4], but due to their exclusively transparent nature their contrast for pressure indication is rather low. We previously demonstrated a pressure sensor based on pressing a flexible membrane against a rigid photonic crystal waveguide [5].…”

Flexible Distributed Pressure Sensing Strip for a Urethral Catheter

“…The top and bottom electrodes are fabricated separately and then assembled together using a channeled-PDMS dielectric. A custom-designed aligner to render the sensor layers to be optically transparent and enable alignment of the layers for assembly is used. Biomedical pressure sensors have previously been developed in literature for cardiac, eye and brain applications ([24], [25], [26]). However, all of these applications involve only a single sensor, and not a series of pressure sensors on a flxible substrate for distributed force measurement.…”