Engineering
Improving Glucose Monitoring Accuracy
Acetaminophen can masquerade as glucose in Medtronic’s continuous glucose monitoring (CGM) sensors, triggering false high readings. I helped develop a novel thin-film membrane that blocks the interferent molecules while letting glucose through, directly boosting sensor reliability.
My Role
Research & Technology Engineering Intern
Duration
3 months
Tools
Spin coating machine, Fourier Transform Infrared Spectroscopy (spectrometer), chronoamperometry and cyclic voltammetry rigs, surface profilometer
Overview
Medtronic Diabetes' Research & Technology team needed a manufacturing-friendly membrane deposition process for their glucose sensors that would selectively reject acetaminophen (interferent), but preserve glucose permeability, minimizing the chance of dangerous false alarms in patient monitoring.
I first screened pure candidate films, then pivoted to polymer composites after fast-fail tests showed brittle films dissolving in glucose. I spin coated varying polymer ratios onto the sensor plate, optimized drying times, and established a rapid 48-sensor test that cycled each sensor through glucose and interferent solutions to evaluate performance in one pass.
Research
Reviewed interference membrane literature and journal articles about materials for interference rejection membranes.
Consulted chemists and engineers to shortlist viable polymers for testing.
Ran small-scale spin coat trials to identify promising composite ratios for full-scale testing.
Design
I tackled the membrane challenge with a structured, end-to-end process: first, I performed quick “fast-fail” spin-coating trials of pure candidate films on clean sensor substrates - cracking or rapid dissolution immediately ruled out brittle formulations. Next, I formulated a matrix of polymer composite blends, applying a simple Design-of-Experiments approach to vary composition and cure times. For each blend, I standardized a spin coating protocol to ensure uniform coverage across all 48 sensors on the test plate. To assess performance, I designed a plate-level sensor test setup that cycled each sensor through glucose and interferent solutions in one run, capturing current responses to measure selective permeability. Using insights from this, I iteratively refined blend ratios, deposition volumes, and surface cleaning steps. Alongside, I used FTIR to confirm film chemistry and voltammetry to validate sensor responses, closing the loop between material formulation, process parameters, and functional performance until the membrane blocked interferents while preserving glucose flux.
Results
Optimized membrane demonstrated reliable interferent rejection and high glucose permeability.
Our in-process test setup accelerated material screening by 180×, enabling rapid iteration and paving the way for pilot scale manufacturing trials.
