Thin Film Biofuel Cathode for RFID Power
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Solution Overview
Problem
There is a need for lightweight, cost-effective power supplies for RFID tags that can be used in various applications, including data measurement and storage, without increasing the size or weight of the tag, and for electrochemical cells that can be stored in an inactive state and activated quickly when needed.
Innovation Solution
A thin film structure comprising a conductive layer with an oxidative enzyme and electron transfer mediator, protected against wetting to allow storage in dry conditions, which becomes active upon contact with an aqueous solution, enabling immediate generation of electric current and suitable for use in biofuel cells and RFID tags.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the thin film layer is made porous to allow immediate enzyme activation, then the activation speed improves, but the storage stability deteriorates due to moisture absorption
Solution Approach 1:
The thin film layer is pre-formed with the oxidizing enzyme and electron transfer mediator in a dry, protected state before use. The porous structure is prepared in advance but kept sealed or protected from moisture until activation, allowing immediate enzyme function upon contact with aqueous solution while maintaining storage stability
Solution Approach 2:
A thin film protective layer is used to seal the porous cathode layer during storage, preventing moisture absorption while allowing the underlying porous structure to remain intact. This thin film barrier protects the enzyme-containing porous layer until activation when the barrier is removed or penetrated, enabling immediate enzyme activation upon aqueous solution contact
2Speed
If the thin film layer is made sufficiently thin for immediate activation, then the activation speed improves, but the enzyme loading capacity decreases
Solution Approach 1:
The cathode layer is designed with a porous structure that provides high surface area and volume for enzyme loading within a thin film configuration. The porosity allows aqueous solution to rapidly penetrate and activate the enzyme throughout the layer while the high surface area maintains sufficient enzyme loading capacity despite the reduced thickness
Solution Approach 2:
The thin film layer is formed as a composite material combining the oxidizing enzyme, electron transfer mediator, and porous matrix structure. This composite approach allows the thin layer to achieve both rapid activation through the porous network and sufficient enzyme capacity through the integrated multi-component structure
3Use of energy by moving object
If conventional power supplies are used for RFID tags, then the power supply capability is sufficient, but the weight and size increase
Solution Approach 1:
The invention employs a disposable biofuel cell with a thin film cathode layer containing oxidizing enzyme and electron transfer mediator. This single-use power source provides sufficient capability for RFID tag operation without the need for rechargeable battery management systems, significantly reducing weight and size while maintaining adequate power supply function
Solution Approach 2:
The power supply is transformed from conventional heavy batteries to a lightweight biofuel cell system. The cathode layer parameters are optimized with specific porosity (40-80%), thickness (1-50 µm), and enzyme-mediator composition to achieve the required power density in a minimal weight and volume configuration suitable for RFID tags
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 thin film structure allows for efficient and immediate activation of enzymes, achieving up to 70-85% of maximum activity within seconds, extending the effective lifetime of electrochemical cells to three weeks and shelf life to one year, while being environmentally friendly and suitable for mass production using printing technology.
Implementation Method 1
a thin layer of a conductive material containing an oxidizing enzyme
Implementation Method 2
an electron transfer mediator mixed with the oxidizing enzyme
Implementation Method 3
The thin layer should be porous enough to allow for an aqueous solution to wick into the layer and efficiently to wet most of the cathode layer
Implementation Method 4
the thin layer is being protected against wetting to allow for its storage in dry conditions
Data Source
Figure 1
Figure 2a~3
Figure 4
AI summary
A thin film structure, which comprises a substrate with a thin conductive layer containing an oxidizing enzyme mixed with an electron transfer mediator. The mixture of the enzyme and the mediator contains a conductive ink which comprises an electrically conductive component selected from the group consisting of carbon nanotubes, metal particles, carbon particles and inherently conductive polymers and mixtures thereof and, optionally, a binder. The thin layer is protected against wetting to allow for its storage in dry conditions, and it is sufficiently porous to allow for immediate activation of the oxidizing enzyme when contacted with an aqueous solution.