Capacitance Sensing for Component Positioning Detection Two-Stage Charger Architecture for Wearable Insulin Pump Pistons

This patent covers a wearable drug delivery device that monitors the position of its pump piston by measuring the capacitance between two terminals (one of them mounted on the piston), using a two-stage charger circuit with two capacitors and two switches to deliver accurate position readings for each pump fill-and-dispense cycle.

The Problem

Patch insulin pumps deliver insulin in very small individual doses, often well below a tenth of a unit. A wearable device the size of a matchbox must repeatedly fill and dispense a tiny shuttle of liquid through a precise piston stroke. At those volumes, small positional errors in the piston translate directly into clinically significant dose errors. Conventional position sensors (optical encoders, mechanical limit switches, magnetic Hall sensors) each have drawbacks in a wearable, water-exposed, disposable device: they consume battery, occupy precious internal volume, are sensitive to humidity and stray fields, or only report end-of-travel rather than position throughout the stroke. The clinical and regulatory need is for a low-power, low-volume, robust positional sensor that verifies the piston has actually completed the intended movement on every cycle, so the algorithm can confirm dose delivery and detect mechanical faults.

What This Invention Does

The invention provides a system, a linear volume shuttle pump, and a method for component positioning detection using capacitance. A first terminal and a second terminal are movable relative to one another, with one of them attached to the pump piston (or specifically to a piston grip). A sensor device measures the capacitance between the two terminals, which changes as the piston moves. The novel part is the two-stage charger circuit that drives the measurement: a first capacitor connects through a first switch to a voltage source, and a second capacitor connects through a second switch to the same source. The controller closes the first switch to charge the first capacitor, then opens the first switch and closes the second switch to charge the second capacitor. The two-stage sequence creates a controlled charge transfer between the reference capacitor and the sense capacitor, from which the system can extract a clean capacitance reading even at the very small absolute capacitances available inside a wearable pump. The controller runs the measurement for each filling and dispensing cycle, so position is verified every stroke. The application is a divisional of AU 2022401512, claiming priority from US Provisional 63/284,150 filed 30 November 2021.

Key Features

• Two-stage charger architecture. Two capacitors and two switches are sequenced under controller control so that the second capacitor is charged from the voltage source only after the first has been charged and isolated, supporting accurate small-capacitance readings.
• Piston-mounted terminal. One of the capacitance terminals is connected to the piston (or piston grip). As the piston moves, the gap between the terminals changes, the capacitance changes, and the sensor reports position throughout the stroke, not only at end-of-travel.
• Per-cycle verification. The controller runs the measurement for every fill and dispense cycle, so the system has a fresh position confirmation for each tiny dose, supporting the dose-by-dose accountability that pump algorithms require for closed-loop insulin delivery.
• Low component count for wearable form factor. The sensor reduces to two capacitors, two switches, a controller, and a voltage source. That is compatible with the constrained PCB area, battery, and disposable cost target of a patch pump.
• Pump architecture coverage. The patent claims both the general system and a specific linear volume shuttle pump embodiment with piston grip integration, locking the IP to the form factor used in Insulet’s Omnipod product family.

Who Is Behind It?

The applicant is Insulet Corporation, the Massachusetts-based maker of the Omnipod tubeless insulin patch pump, including the Omnipod 5 automated insulin delivery system. The named inventors are Kepei Sun, Benjamin Lacroix, Steven Cardinali, Kyle Breingan, Jerry Witt, Carolyn Reistad, and Nicholas Conte, a team consistent with Insulet’s hardware and sensors engineering organisation. The Australian patent attorney is Davies Collison Cave in Melbourne. The application is a divisional of AU 2022401512, claiming priority from US provisional 63/284,150 filed 30 November 2021.

Why It Matters

Insulin pumps and automated insulin delivery systems are the dominant non-pancreatic therapy for type 1 diabetes and an increasingly important option in insulin-requiring type 2 diabetes. Approximately 130,000 Australians live with type 1 diabetes; Omnipod competes against Medtronic‘s MiniMed and Tandem‘s t:slim X2 in the local market, with reimbursement available through the National Diabetes Services Scheme. Continuous improvement of pump fidelity, low-cost sensing, and dose accuracy is the engineering battleground that decides regulatory clearance, formulary listing, and patient preference. Patent protection over an accurate, low-power, low-area piston position sensor is operationally central to Insulet’s hardware roadmap and to its ability to defend against competing pumps and closed-loop systems that may converge on similar designs.

Related Concepts

This invention is part of the broader push toward the artificial pancreas, in which an insulin pump and a continuous glucose monitor talk to each other in a closed loop to automate insulin dosing for people with type 1 diabetes.

Underneath the medical use, this is fundamentally a capacitive sensing design problem: getting a clean, low-noise position reading from a tiny capacitor inside a disposable, battery-powered wearable.

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AU 2026201861 was published in the Australian Official Journal of Patents on 2 April 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.