Graphene Oxide Hydrogel Composites for Infrared-Driven Actuation

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Solution Overview

Problem

Conventional light-responsive hydrogels, such as those incorporating gold nanoparticles, exhibit limited volumetric changes, restricting their potential as actuators in microfluidic and microlens applications due to insufficient responsiveness.

Innovation Solution

Composite hydrogels are developed by dispersing and covalently bonding graphene oxide flakes into thermo-responsive polymers, enhancing their swelling ratio and responsiveness through improved thermal conductivity and photothermal conversion, allowing for remote activation with infrared light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If gold nanoparticles are incorporated into thermo-responsive hydrogels to achieve light responsiveness, then the hydrogels can respond to infrared light stimulation, but the volumetric change is not significantly enhanced, limiting actuator performance

Engineering Contradiction:

Improvelight responsivenessVSAvoidvolumetric change

Core Design Contradiction:

Adaptability or versatilityVSVolume of moving object

Solution Approach 1:

The patent creates a composite hydrogel system combining thermo-responsive polymer chains (PNIPAAm) with infrared-absorbing nanoparticles (graphene oxide, carbon nanotubes, or gold nanoparticles). This composite structure enables dual functionality: the polymer provides temperature-responsive swelling/deswelling behavior while the infrared-absorbing particles enable remote optical control, achieving both light responsiveness and significant volumetric changes (>40% swelling ratio) that neither component could achieve alone.

Inventive Principle:

Principle #40Composite materials

2Volume of moving object

If conventional thermo-responsive hydrogels are used without infrared-absorbing particles, then they exhibit significant volumetric changes with temperature, but they cannot be remotely activated by light

Engineering Contradiction:

Improvevolumetric changeVSAvoidlight responsiveness

Core Design Contradiction:

Volume of moving objectVSAdaptability or versatility

Solution Approach 1:

The patent introduces infrared-absorbing nanoparticles as intermediary agents that convert optical energy into thermal energy, which then triggers the thermo-responsive polymer chains. These nanoparticles act as mediators between the light source and the polymer, enabling remote noninvasive activation without direct thermal contact, thus achieving both significant volumetric changes and light responsiveness.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the hydrogel is swollen to block fluid flow in microfluidic devices, then effective valve control is achieved, but the device requires larger space for the actuator

Engineering Contradiction:

Improvevalve control effectivenessVSAvoidactuator volume

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent exploits the dramatic reversible parameter change in the hydrogel's volume and density in response to temperature changes. By using the composite hydrogel's ability to transition between highly swollen (blocking flow) and collapsed (allowing flow) states, the valve achieves effective control with minimal actuator volume, as the same material provides both the blocking function when swollen and the compact storage state when deswollen.

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

The composite hydrogels demonstrate significantly increased swelling ratios and rapid volumetric changes, making them suitable for actuator applications in micro- and nano-scale devices, such as microfluidic valves and tunable microlenses, with reduced material volume requirements.

Implementation Method 1

The composite hydrogels are characterized by swelling ratios that are larger than the swelling ratios of their hydrogel polymers in the absence of the graphene oxide flakes at temperatures below the LCST. This enhanced swelling ratio renders the composite hydrogels well-suited for use as actuators in micro- and nano-scale devices.

Methodology Applied

Scientific EffectInfrared absorption and photothermal conversion: Absorption (EM radiation)

Implementation Method 2

The light response is realized by combining the reversible hydration-dehydration transition of NIPAAm and the plasmonic absorption band in the near-infrared (IR) region of AuNPs.

Methodology Applied

Scientific EffectHydration-dehydration transition: Phase Change

Implementation Method 3

The composite hydrogels demonstrate significantly higher swelling ratios and rapid volumetric changes in response to temperature changes

Methodology Applied

Scientific EffectThermal expansion and contraction: Thermal Expansion

Implementation Method 4

The light response is realized by combining the reversible hydration-dehydration transition of NIPAAm and the plasmonic absorption band in the near-infrared (IR) region of AuNPs.

Methodology Applied

Scientific EffectPlasmonic absorption: Absorption (EM radiation)

Data Source

PatentUS20130137054A1Infrared light- and thermal-responsive graphene oxide hydrogel polymer composites

Publication Date: 2013.05.30 WISCONSIN ALUMNI RES FOUND

AI summary

Composite hydrogels and methods for making and using the composite hydrogels are provided. The composite hydrogels comprise graphene oxide flakes distributed in, and covalently bonded to, a thermo-responsive hydrogel polymer.