Flexible Micro-TEG Fabrication via Electroplating
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Solution Overview
Problem
Existing methods for fabricating flexible thermoelectric generators (TEGs) face challenges in achieving high power density due to large electrical resistance and complex production processes, particularly when attempting to create cross-plane structures on flexible substrates without rigid substrates.
Innovation Solution
A method involving electroplating and microfabrication processes on a semi-rigid or rigid substrate, followed by substrate transferring, to form cross-plane flexible micro-TEGs with low internal resistance, using a bottom-up approach with polyimide layers and electroplating of thermoelectric pillars, allowing for high power density and commercial viability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If flexible TEGs are fabricated using printing, evaporation, or sputtering techniques, then mechanical flexibility is achieved, but electrical resistance becomes large and power density becomes low
Solution Approach 1:
The patent replaces conventional mechanical deposition techniques (printing, evaporation, sputtering) with electrochemical electroplating to fabricate thermoelectric legs. This substitution enables precise control of material composition and structure, achieving low electrical resistance while maintaining mechanical flexibility through the use of flexible substrates and thin-film structures.
Solution Approach 2:
The patent changes the fabrication parameters by using electroplating with controlled deposition conditions to achieve optimized thermoelectric material properties. By controlling electroplating parameters such as current density, deposition time, and electrolyte composition, the patent achieves low electrical resistance and high power density while maintaining flexibility.
2Adaptability or versatility
If cross-plane TEG structure is fabricated without rigid substrates, then mechanical flexibility is improved, but fabrication complexity increases and manufacturing difficulty arises
Solution Approach 1:
The patent applies preliminary action by first fabricating the complete cross-plane TEG structure on a rigid substrate using electroplating, then transferring the finished device to a flexible substrate. This preliminary fabrication on a rigid platform simplifies the manufacturing process while achieving the final flexible configuration, avoiding the complexity of direct flexible fabrication.
Solution Approach 2:
The patent uses a rigid substrate as an intermediary platform during fabrication. The rigid substrate facilitates precise electroplating and assembly of the cross-plane structure, after which the completed device is transferred to the flexible substrate. This intermediary approach decouples the fabrication complexity from the final flexible configuration.
3Ease of manufacture
If in-plane TEG structure is used, then fabrication is simplified, but power density becomes low due to low density of thermoelectric pairs and parasitic heat flow
Solution Approach 1:
The patent inverts the conventional in-plane structure by adopting a cross-plane configuration where thermoelectric legs are vertically oriented between hot and cold reservoirs. This inversion increases the density of thermoelectric pairs in the active area and reduces parasitic heat flow through the substrate, thereby achieving high power density while maintaining fabrication simplicity through electroplating.
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 method achieves a high power density for flexible TEGs with low internal resistance, enabling them to maintain performance even when bent, and is scalable for commercial production, suitable for wearable devices.
Implementation Method 1
forming a flexible TEG supported on a flexible substrate by electroplating, at least in part, each of a plurality of bottom interconnectors, a plurality of p-type and n-type thermoelectric pillars, and a plurality of top interconnectors
Implementation Method 2
Thermoelectric generators (TEGs) are promising devices for waste heat recovery by virtue of their ability to directly convert heat to electricity
Data Source
AI summary
A cross-plane flexible micro-TEG with hundreds of pairs of thermoelectric pillars formed via electroplating, microfabrication, and substrate transferring processes is provided herein. Typically, fabrication is conducted on a Si substrate, which can be easily realized by commercial production line. The fabricated micro-TEG transferred to the flexible layer from the Si substrate. Fabrication methods provided herein allow fabrication of main TEG components including bottom interconnectors, thermoelectric pillars, and top interconnectors by electroplating. Such flexible micro-TEGs provide high output power density due to high density of thermoelectric pillars and very low internal resistance of electroplated components. The flexible micro-TEG can achieve a power per unit area of 4.5 mW cm−2 at a temperature difference of ˜50 K, which is comparable to performance of flexible TEGs developed by screen printing. The power per unit weight of flexible TEGs described herein is as high as 60 mW g−1, which is advantageous for wearable applications.