Wireless IOP Sensor Readout With Repeater Coil and Ferrite Coupling
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Solution Overview
Problem
Existing intraocular pressure (IOP) sensors have a short working distance and require stringent alignment with external readout circuits, limiting their use in point-of-care applications due to low quality factor of planar spiral inductors and bulky, expensive external readouts.
Innovation Solution
A wireless interrogated MEMS capacitive IOP sensor with a novel readout circuit and soft-magnetic ferrites for improved magnetic coupling, integrated into an oscillator for point-of-care use, and a repeater coil to enhance signal strength and relax alignment tolerances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If planar spiral inductors are used in IOP sensors, then the sensor can be fabricated with standard processes, but the quality factor is low which limits resolution
Solution Approach 1:
The patent changes the inductor geometry from planar spiral to three-dimensional stacked spiral structure, fundamentally altering the physical parameter of inductance realization. This 3D structure provides higher quality factor while maintaining compatibility with standard CMOS fabrication processes, thus resolving the contradiction between ease of manufacture and measurement precision.
2Measurement precision
If external readout circuit is used to measure frequency and phase response, then accurate IOP measurement is achieved, but the equipment is bulky and expensive
Solution Approach 1:
The patent implements self-service by integrating the readout circuit directly into the sensor chip. The sensor becomes self-contained with onboard processing capabilities, eliminating the need for bulky external equipment. The integrated readout circuit performs frequency and phase measurement functions locally, reducing system complexity while maintaining measurement accuracy.
Solution Approach 2:
The patent merges the sensor functionality with the readout circuit functionality into a single integrated chip. By combining what were previously separate components (sensor element and external readout equipment) into one unified device, the system achieves compact form factor while preserving measurement capabilities.
3Reliability
If short working distance is used in IOP sensors, then magnetic coupling is strong, but the sensor requires stringent alignment with external readout
Solution Approach 1:
The patent employs dynamic tuning mechanisms that allow the sensor to adapt its operating characteristics in real-time. This enables the system to maintain optimal magnetic coupling despite variations in positioning, effectively relaxing alignment requirements while preserving coupling strength through active adjustment rather than static precision.
Solution Approach 2:
The patent utilizes variable inductance and capacitance elements that can dynamically adjust their values to optimize the resonant frequency and magnetic coupling conditions. By changing these electrical parameters, the system compensates for positional variations and maintains reliable coupling without requiring stringent mechanical alignment.
4Reliability
If repeater coil is integrated into oscillator for point-of-care readout, then signal strength is enhanced and alignment tolerance is relaxed, but device complexity increases
Solution Approach 1:
The patent designs the integrated oscillator to serve multiple functions: it acts as both the timing reference and the signal generation mechanism for the repeater coil, while also providing the readout functionality. This multi-functionality reduces the need for separate dedicated components, thereby enhancing signal strength without proportionally increasing device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables real-time, continuous IOP monitoring with a detection range of 0 mmHg to 50 mmHg and resolution of 0.1 mmHg, facilitating patient self-testing and reducing the need for bulky external equipment.
Implementation Method 1
a pressure sensor including a sealed or encapsulated parallel-plate capacitor with a deformable membrane... the capacitance changes lead to a change in the amplitude and phase of frequency of the LC-tank circuit
Implementation Method 2
an external reader outside the subject's eye configured to wirelessly interrogate the pressure sensor and detect changes in resonant frequency and phase
Implementation Method 3
soft-magnetic ferrites for improved magnetic coupling... addition of soft-magnetic ferrite materials to enhance magnetic resonance
Implementation Method 4
repeater coil to enhance signal strength... strategically designed to result in improved signal strength while relaxing the needed accuracy in terms of position and angle alignment tolerance
Data Source
AI summary
Disclosed herein are implantable sensors, including intraocular (IOP) pressure sensors suitable for continuous pressure monitoring and point-of-care applications, and methods of manufacture and use. In some implementations, the incorporation of repeater coil(s) as intermediate relays and addition of soft-magnetic ferrite materials to enhance magnetic resonance is strategically designed to result in improved signal strength while relaxing the needed accuracy in terms of position and angle alignment tolerance.