Implantable Sensor Calibration via Multi-Reservoir Mixer
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Solution Overview
Problem
Current continuous analyte monitoring systems, such as continuous glucose monitors, suffer from diminished accuracy and reliability due to foreign body response and contamination, requiring frequent calibration with invasive methods, and existing in situ calibration methods are limited by single-point calibration and fixed reservoirs, leading to potential calibration errors.
Innovation Solution
A subcutaneous sensor system with multiple reservoirs and a controller that allows for programmable calibration solutions, enabling two-point calibration and a safety check, as well as cleaning of the sensor, to improve accuracy and reliability by using a mixer to combine calibration solutions and calculate the sensor's transfer function for precise glucose measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If implantable sensors are used for continuous analyte monitoring, then real-time glucose levels can be monitored, but accuracy and precision diminish over time due to foreign body response and contamination
Solution Approach 1:
The system performs calibration by delivering known concentrations of analyte to the sensor before actual monitoring begins. This preliminary calibration establishes accurate transfer functions that account for sensor characteristics and minimize drift effects during subsequent continuous monitoring operations.
Solution Approach 2:
The system changes the concentration parameter of calibration solutions delivered to the sensor, using multiple different known concentrations to establish a comprehensive transfer function. This allows the system to accurately map sensor responses across the full range of expected analyte levels, improving measurement precision throughout the monitoring period.
2Measurement precision
If frequent calibration is performed to maintain accuracy, then measurement precision improves, but patient convenience deteriorates due to invasive finger stick requirements
Solution Approach 1:
The system performs self-calibration by automatically delivering known calibration concentrations to the implanted sensor and using the sensor's own response to establish accurate transfer functions. This eliminates the need for patients to perform invasive finger stick calibrations, as the system calibrates itself internally using programmable pump delivery of calibration solutions.
Solution Approach 2:
The system uses an intermediary calibration solution delivered through a programmable pump to bridge the gap between known reference values and sensor measurements. This intermediary substance allows calibration without requiring patient blood samples, maintaining accuracy while improving convenience.
3Ease of operation
If single-point calibration is used to simplify the process, then ease of operation improves, but measurement precision deteriorates due to potential calibration errors
Solution Approach 1:
The calibration process is segmented into multiple discrete steps, each delivering a different known concentration of analyte to the sensor. Instead of a single calibration point, the system sequentially presents multiple concentration levels (e.g., low, medium, high) to establish a more robust and accurate transfer function that better captures sensor behavior across the full measurement range.
Solution Approach 2:
The system performs more calibration actions than the minimum single-point requirement by delivering multiple calibration concentrations. This excessive calibration effort ensures accurate transfer function establishment across the entire operating range, compensating for potential non-linearities and improving overall measurement precision without significantly increasing patient burden.
Data Source
AI summary
A subcutaneous sensor system includes a sensor, a plurality of reservoirs, a plurality of pumps, a mixer provided with a plurality of mixer inlets and a mixer outlet, and a controller having an input coupled to the sensor output and a plurality of control outputs coupled to the plurality of pumps and the mixer. In certain embodiments, the system further includes an enclosure for the reservoirs, the pumps, the mixer and the controller, e.g. in the form of a skin patch or in the form of an implantable enclosure. In certain embodiments, the sensor is external to the enclosure and implanted beneath the skin tissue.