Laser-Ablated LC Humidity Sensor for Low-Cost Food Packaging
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Solution Overview
Problem
Existing humidity sensors for food packaging are economically infeasible due to high component costs and complex manufacturing processes, and they lack sensitivity and flexibility for real-time moisture monitoring, leading to inefficiencies in food spoilage detection.
Innovation Solution
A wireless humidity sensor is fabricated using laser ablation to create an inductive-capacitive resonant circuit directly on a metalized substrate, utilizing a spiral inductor and interdigitated capacitor, which is sensitive to moisture changes and can be produced cost-effectively through scalable manufacturing processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional humidity sensors are used for food packaging, then humidity monitoring capability is provided, but component costs and manufacturing complexity increase significantly
Solution Approach 1:
The patent replaces traditional electronic humidity sensing components with a mechanical resonant circuit fabricated directly on packaging material. The inductive-capacitive resonant circuit uses physical geometric structures (spiral inductor, interdigitated capacitor) whose resonant frequency shifts in response to humidity, eliminating the need for complex electronic sensors while maintaining measurement capability
Solution Approach 2:
The packaging material serves multiple functions simultaneously: it provides structural containment, acts as the substrate for the resonant circuit, and enables humidity sensing through the resonant frequency shift. This multi-functionality integrates the sensing capability into the packaging itself rather than requiring separate sensor components
2Measurement precision
If traditional humidity sensors are used for food packaging, then humidity monitoring capability is provided, but component costs increase
Solution Approach 1:
The resonant circuit is fabricated directly on inexpensive packaging materials using cost-effective techniques such as laser ablation or printing. The entire sensing structure can be produced as a disposable component integrated into single-use packaging, eliminating the need for expensive reusable sensor components
Solution Approach 2:
The patent replaces expensive electronic humidity sensor components with a mechanical resonant circuit that uses the physical properties of the packaging material itself. The resonant frequency detection method requires only simple electromagnetic excitation and measurement equipment, reducing overall system cost
3Ease of manufacture
If laser ablation is used to create the resonant circuit, then manufacturing cost and scalability improve, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes the resonant circuit geometry parameters (spiral inductor dimensions, interdigitated capacitor finger spacing and width) to achieve the desired resonant frequency range. By carefully controlling these geometric parameters during laser ablation, precise resonant frequencies can be achieved even with moderate manufacturing tolerances
Solution Approach 2:
The laser ablation process creates slightly larger features than the minimum required dimensions, then uses subsequent processing steps (such as chemical etching or mechanical trimming) to achieve the final precise dimensions. This approach allows the use of robust, scalable laser ablation while still achieving the necessary manufacturing precision
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 sensor provides high sensitivity to moisture changes, enabling efficient and cost-effective real-time monitoring of humidity levels in food packaging, reducing food spoilage and waste by extending shelf life.
Implementation Method 1
laser ablation to create an inductive-capacitive resonant circuit directly on a metalized substrate
Implementation Method 2
inductive-capacitive resonant circuit... sensitive to moisture changes
Data Source
AI summary
A humidity sensor may include a metalized substrate comprising a laser ablated portion and a remaining metal portion. The remaining metal portion may include a spiral inductor and an interdigitated capacitor. The interdigitated capacitor may be coupled in parallel with the spiral inductor. The interdigitated capacitor may be centrally positioned with respect to the spiral inductor and surrounded by spirals of the spiral inductor. The spiral inductor and interdigitated capacitor may be formed by selectively ablating the metallized substrate to define the inductor and capacitor.