Chemically Driven Auto-Injector Retraction for Viscous Fluids

Solution Overview

Problem

Existing auto-injectors face challenges in delivering high-concentration, high-viscosity protein therapeutics due to structural limitations, energy storage issues, and inability to modify pressure profiles, leading to potential damage and patient anxiety.

Innovation Solution

The use of gas-generating chemical reactions to power auto-injectors, allowing for compact design and adjustable pressure delivery, enabling self-administration of high-viscosity fluids with minimal discomfort.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Force

If spring-driven mechanisms are used to deliver high-viscosity fluids, then delivery force can be achieved, but device footprint becomes large and plastic parts may be damaged due to stored energy

Engineering Contradiction:

Improvedelivery forceVSAvoiddevice footprint

Core Design Contradiction:

ForceVSArea of stationary object

Solution Approach 1:

The patent replaces the traditional spring-driven mechanical system with a pneumatic system that uses gas generation to drive fluid delivery. This substitution eliminates the need for large springs and associated plastic components, reducing device footprint while maintaining delivery capability for high-viscosity fluids.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the energy storage parameter from mechanical spring potential energy to pneumatic pressure energy. By generating gas on-demand and using it to pressurize the fluid, the system achieves force delivery without the structural constraints of spring mechanisms, allowing for more compact design.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If spring energy is stored to deliver high-viscosity fluids, then delivery reliability improves, but plastic parts may be damaged due to creep under stress

Engineering Contradiction:

Improvedelivery reliabilityVSAvoidplastic part strength

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent replaces the spring-driven mechanical system with a pneumatic system that uses gas generation to drive fluid delivery. This substitution eliminates the need for large springs and associated plastic components, reducing device footprint while maintaining delivery capability for high-viscosity fluids.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system uses a compliant membrane or bellows to cushion and regulate the pneumatic pressure, preventing sudden pressure spikes that could damage plastic components. This cushioning element absorbs excess energy and ensures controlled force application to the fluid.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Ease of operation

If conventional spring auto-injectors are used, then injection can be achieved, but patient anxiety increases due to operational sound

Engineering Contradiction:

Improveinjection capabilityVSAvoidpatient anxiety

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the spring-driven mechanical system with a pneumatic system that uses gas generation to drive fluid delivery. This substitution eliminates the need for large springs and associated plastic components, reducing device footprint while maintaining delivery capability for high-viscosity fluids.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The system uses controlled, periodic gas generation rather than continuous spring compression, allowing for quieter operation. The gas is generated in controlled bursts that are less audible than the rapid decompression of springs, reducing patient anxiety.

Inventive Principle:

Principle #19Periodic action

4Force

If spring-driven mechanisms are used, then injection force can be delivered, but pressure profile cannot be modified for fine-tuning delivery

Engineering Contradiction:

Improveinjection forceVSAvoidpressure profile adjustability

Core Design Contradiction:

ForceVSAdaptability or versatility

Solution Approach 1:

The invention changes the energy storage parameter from mechanical spring potential energy to pneumatic pressure energy. By generating gas on-demand and using it to pressurize the fluid, the system achieves force delivery without the structural constraints of spring mechanisms, allowing for more compact design.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The system uses a controllable gas generation mechanism that can dynamically adjust pressure output. By varying the rate and amount of gas generated, the system can fine-tune the pressure profile to match specific delivery requirements, unlike fixed spring mechanisms.

Inventive Principle:

Principle #15Dynamics

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 reliable, self-administration of high-concentration protein therapeutics with reduced anxiety and improved patient compliance through controlled gas generation and needle retraction.

Implementation Method 1

gas-generating chemical reactions to power auto-injectors

Methodology Applied

Scientific EffectGas-generating chemical reaction: Chemical Bonding

Implementation Method 2

pressurizing the first chamber of the barrel with the generated gas

Methodology Applied

Scientific EffectGas pressure: Pressure Increase

Implementation Method 3

a chemical reaction is initiated in a reaction chamber to produce a gas, and the gas acts upon a piston to deliver the fluid

Methodology Applied

Scientific EffectChemical reaction: Chemical Bonding

Data Source

PatentEP3658208B1Chemically driven auto-injector with retraction

Publication Date: 2025.08.27 ELI LILLY & CO

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AI summary

Automatic injection devices (i.e., auto-injectors) and methods are disclosed that use gas-generating chemical reactions for parenteral delivery of therapeutic fluids. The generated gas may place the auto-injector in a punctured configuration to puncture a patient's skin with a needle, an injected configuration to deliver the therapeutic fluid through the needle and into the puncture site, and/or a retracted configuration to withdraw the needle from the puncture site.