Inductive Piston Position Sensing in Drug Delivery Apparatus
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Solution Overview
Problem
Existing drug delivery apparatuses lack precision in quantifying the amount of substance administered, especially in challenging environments, and are often cumbersome, costly, and impractical for field use due to reliance on electromechanical systems.
Innovation Solution
A drug delivery apparatus utilizing inductance interactions between a piston and a stacked coil antenna to quantify substance delivery externally and non-invasively, independent of substance characteristics, without contact, and compatible with conventional dispensing mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If visual inspection of graduated marks is used to measure substance volume, then the apparatus structure remains simple, but measurement precision deteriorates in challenging environments (transparent substances, lack of luminosity, substance traces)
Solution Approach 1:
The patent replaces the mechanical/optical visual inspection system with an electromagnetic measurement system. A coil antenna generates an electromagnetic field that interacts with the conductive piston, and changes in electrical impedance are measured to determine piston position and substance volume. This substitution eliminates the need for visual inspection of graduated marks, providing precise measurement independent of substance transparency, lighting conditions, or substance traces.
Solution Approach 2:
The patent introduces an electromagnetic field as an intermediary between the measurement system and the piston. The coil antenna generates an electromagnetic field that penetrates the barrel and interacts with the conductive piston without physical contact. This intermediary field enables indirect measurement of piston position through electrical impedance changes, avoiding direct contact with the substance while maintaining measurement precision.
2Measurement precision
If electromechanical measurement systems are used to quantify substance delivery, then measurement precision improves, but device complexity, weight, and cost increase making them impractical for field use
Solution Approach 1:
The patent replaces complex electromechanical measurement systems (such as encoders, potentiometers, or optical sensors) with a simple electromagnetic induction system. The coil antenna and conductive piston create an inductive coupling system where piston position is determined by measuring electrical impedance changes. This simplified system dramatically reduces device complexity, weight, and cost while maintaining measurement precision, making it suitable for portable field use.
Solution Approach 2:
The conductive piston serves a dual function: it is both the actuating element that pushes the substance and the sensing element that interacts with the electromagnetic field for position measurement. This self-service approach eliminates the need for separate measurement components, reducing overall system complexity while enabling precise quantification of substance delivery.
3Measurement precision
If contactless electromagnetic measurement is used, then substance contamination is prevented and measurement precision improves, but device complexity increases due to additional antenna and control systems
Solution Approach 1:
The coil antenna serves multiple functions simultaneously: it generates the electromagnetic field for measurement, acts as the sensing element for detecting piston position through impedance changes, and provides the signal processing interface. This multi-functionality reduces the need for separate components, minimizing the increase in device complexity while achieving contactless measurement and substance contamination prevention.
4Measurement precision
If stacked coil antenna configuration is used, then measurement precision and signal strength improve, but antenna size and weight increase
Solution Approach 1:
The patent employs a stacked coil configuration where multiple coils are arranged concentrically or in layers along the piston course. This nested arrangement allows the coils to share space efficiently, increasing the electromagnetic interaction strength and measurement precision without proportionally increasing the overall antenna volume or weight. The nested structure maximizes the measurement field while minimizing material usage.
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
Provides precise, external, and non-invasive quantification of substance delivery, minimizing resources and weight, while ensuring accurate dosing and preventing contamination, and can be integrated with existing systems without modification.
Implementation Method 1
the antenna being composed of a plurality of coils stacked on top of each other along the piston course, each coil being electrically connected to one another and to a supply circuit configured to provide an input current to the coils
Data Source
Figure 1A
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Figure 2
AI summary
A drug delivery apparatus including a barrel to contain a substance, a piston slidable in the barrel, a supply circuit to provide input currents, an antenna affixed along the barrel to receive the input current, generate inductance with the piston, and provide output currents commensurate with a position of the piston along the piston course, and processing circuitry configured to receive the output currents, and determine a quantity of the substance inside the barrel based on the output currents.