SMA Actuated Implantable Pump for MRI Compatibility

Solution Overview

Problem

Implantable drug delivery systems with solenoid-based valve assemblies are susceptible to magnetic fields, causing the metering function to be bypassed during MRI procedures, necessitating patients to empty the pump reservoir before undergoing MRI scans.

Innovation Solution

Replacement of solenoids with Shape Memory Alloy (SMA) wires and associated control electronics, which expand and contract based on temperature changes, allowing the metering assembly to function independently of magnetic fields by using electrical current to actuate the valves.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Extent of automation

If solenoid-based valve assemblies are used in implantable drug delivery systems, then the metering function can be controlled electronically, but the system becomes susceptible to magnetic fields during MRI procedures

Engineering Contradiction:

Improveelectronic control of metering functionVSAvoidsusceptibility to magnetic fields

Core Design Contradiction:

Extent of automationVSObject-affected harmful factors

Solution Approach 1:

The patent replaces solenoid-based electromagnetic valve actuation with a shape memory alloy (SMA) based mechanical actuation system. The SMA wire undergoes phase transformation when heated by electrical current, causing mechanical contraction that directly actuates the valve without relying on electromagnetic fields. This substitution eliminates the harmful interaction with MRI magnetic fields while maintaining electronic control capability through electrical heating of the SMA material.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the actuation mechanism from electromagnetic field-based (solenoid) to thermal field-based (shape memory alloy). By utilizing the temperature-dependent phase transformation properties of SMA materials, the system achieves valve actuation through thermal parameters rather than electromagnetic parameters, thereby avoiding susceptibility to MRI magnetic fields while maintaining programmable electronic control.

Inventive Principle:

Principle #35Parameter changes

2Object-affected harmful factors

If patients empty the pump reservoir before MRI procedures, then the magnetic field susceptibility problem is avoided, but the system loses operational capability during MRI procedures

Engineering Contradiction:

Improvemagnetic field interferenceVSAvoidoperational capability during MRI

Core Design Contradiction:

Object-affected harmful factorsVSAdaptability or versatility

Solution Approach 1:

The patent replaces solenoid-based electromagnetic valve actuation with a shape memory alloy (SMA) based mechanical actuation system. The SMA wire undergoes phase transformation when heated by electrical current, causing mechanical contraction that directly actuates the valve without relying on electromagnetic fields. This substitution eliminates the harmful interaction with MRI magnetic fields while maintaining electronic control capability through electrical heating of the SMA material.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the actuation mechanism from electromagnetic field-based (solenoid) to thermal field-based (shape memory alloy). By utilizing the temperature-dependent phase transformation properties of SMA materials, the system achieves valve actuation through thermal parameters rather than electromagnetic parameters, thereby avoiding susceptibility to MRI magnetic fields while maintaining programmable electronic control.

Inventive Principle:

Principle #35Parameter changes

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 the implantable drug delivery system to remain operational in strong magnetic fields, such as those encountered during MRI procedures, without the need for patients to empty the pump reservoir.

Implementation Method 1

Replacement of solenoids with Shape Memory Alloy (SMA) wires and associated control electronics, which expand and contract based on temperature changes

Methodology Applied

Scientific EffectShape Memory Alloy: Shape Memory Alloy

Implementation Method 2

using electrical current to actuate the valves

Methodology Applied

Scientific EffectJoule Heating: Joule Heating

Data Source

PatentEP2307076B1MRI compatible programmable valve pump

Publication Date: 2019.05.01 FLOWONIX MEDICAL INC

Figure 1
Figure 2
Figure 3

AI summary

An implantable drug delivery system utilizing a non-magnetic valve/accumulator metering assembly is disclosed. The solenoids of the prior art, which respond to magnetic fields, are replaced by Shape Memory Alloy (SMA) wires and associated control electronics. By exploiting the inherent characteristics of SMA wires, which can expand and contract based on their temperature, the movements required to actuate the metering assembly can be achieved. This configuration retains the benefits associated with the prior art, while eliminating the major drawback.