Norbert Willenbacher | Karlsruhe Institute of Technology: How can we engineer polymer-free contact regions in metal-polymer composite pastes?

Can adding trace amounts of a secondary fluid fundamentally rewrite the rules of electrical percolation?

Capillary suspensions present a breakthrough ternary fluid-fluid-solid paradigm that challenges conventional binary composite formulations. By introducing trace amounts of an immiscible secondary fluid to a pre-existing suspension, a capillary-driven network is formed. This physical phenomenon abruptly transitions a low-viscosity, fluid-like system into a gelled, cream-like network.

On a microscopic scale, the secondary liquid acts as a physical bridge, capillary-binding the solid conductive particles together. This capillary-induced self-assembly forces the particles into a continuous path, bypassing random spatial distribution and creating an optimized conductive network.

This structural reorganization drastically shifts the percolation threshold to much lower volume fractions. Consequently, manufacturers can achieve superior electrical conductivity with significantly lower filler concentrations, dramatically reducing material costs without sacrificing performance.

In this short video, you can learn:
* The physical mechanism behind ternary fluid-fluid-solid capillary suspensions.
* How trace secondary fluids induce particle network self-assembly.
* The massive impact of capillary bridging on shifting the electrical percolation threshold.

📋 **Clip Abstract** This clip explains the fundamental physics of capillary suspensions and how they restructure particulate networks. It demonstrates how adding trace immiscible liquids shifts the electrical percolation threshold to achieve high conductivity at low filler loadings.

Can we slash silver consumption in conductive adhesives down to 7% without losing electrical pathing?

High silver price volatility is a critical bottleneck for scaling perovskite-silicon tandem solar cells. To address this, researchers are developing low-silver electrically conductive adhesives (ECAs) that systematically replace solid silver flakes. By substituting pure silver with silver-coated glass particles, the silver content can be dropped to 25% while maintaining printability and conductivity.

Stepping down even further, utilizing silver-coated copper cores allows the total silver content of the ECA formulation to plunge to a mere 7%. While these copper-core composites show excellent initial performance comparable to pure silver systems, they suffer from degradation over accelerated thermal cycling due to oxidation issues.

Overcoming these environmental stability issues requires careful optimization of the core-shell coating integrity and resolving chemical interactions between the copper and the epoxy matrix. Successfully mitigating these issues will unlock ultra-low-cost, highly stable metallization pathways for the next generation of PV modules.

In this short video, you can learn:
* Strategies to replace bulk silver flakes with engineered core-shell particles like silver-coated glass.
* The transition to copper-core, silver-shell architectures to achieve 7% silver loadings.
* The degradation and oxidation challenges associated with copper-based conductive fillers in thermal cycling.

📋 **Clip Abstract** This clip investigates the development of ultra-low-silver conductive adhesives using silver-coated glass and copper core-shell particles. It highlights the trade-offs between cost reduction and long-term thermal cycling stability due to copper oxidation.