Abstract
Purpose :
The recent developments in micro-machining and implantable opto-electronic devices have enabled the integration of flexible sensors and circuits on ophthalmic platforms. This work presents an embedded smart platform based on a capacitive-based flexible pressure sensor for real-time intraocular pressure (IOP) monitoring.
Methods :
The fabrication process of the pyramid-microstructured parallel-plate capacitor involves three main steps: silicon mold preparation, PDMS molding, and lamination of the ITO/PET electrodes. A 10x10 pyramid microstructure array, with a base length of 50 μm and spacing of 100 μm, was simulated, fabricated and tested for a 1.5 mm square area. Using COMSOL Multiphysics, a generalized simulation model was developed to analyze pyramid deformation and capacitance changes within a pressure range of 0-60 mmHg. Pressure sweeps and cycling tests were conducted with two experimental setups: (i) compression using a linear stage and a force gauge and (ii) inflation with a close-loop IOP control system on a synthetic model eye (BIONIKO). Simultaneously, capacitance was measured using an LCR monitor.
Results :
The miniaturized flexible pressure sensor has total dimensions of 1.5x1.5 mm with a thickness of 305±12 μm. The pyramid base and spacing closely align with the design, deviating by less than 2 μm across the entire area. The fabrication process consistently reproduces the final platform configuration with high repeatability. Under increased pressure, the two parallel-plate electrodes approached, resulting in an increase of the sensor’s capacitance. Comparative analysis of simulations and experimental results with the fabricated sensors revealed initial capacitance and sensitivity of 0.47 pF / 0.22 kPa-1 (simulations) and 0.21-0.44 pF / 0.06-0.18 kPa-1 (experimental). Inflation tests showed higher variation in initial capacitance and sensitivity compared to compression tests. Cycle compression measurements demonstrated the pressure sensor's stability in response and relaxation times.
Conclusions :
We have successfully demonstrated the fabrication of a miniaturized smart intraocular platform with a pyramidal microstructure, demonstrating its potential for real-time intraocular pressure (IOP) monitoring. Ongoing research is needed to determine active sensor's lifespan and explore encapsulation materials for its final integration into an intraocular implant.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.