used to make electrocatalytic water splitting processes more efficient. Hybrid metal foams may have favorable conductive properties for flexible devices. Through the application of a thin layer of metal onto a porous polymer substrate via gas-phase deposition, researchers have been able to achieve high conductivity while maintaining the flexibility of the polymer matrix. Through cycling testing, it has been shown that hybrid foams are capable of surface deformation sensing. Future efforts seek to characterize the change in cross-linking and porosity of materials as deposition occurs. Additionally, the interaction or compatibility between different polymers and metals in foam ligands can be explored in order to get an improved understanding of their sensitivity to external forces. This would help improve resistance to compressive forces. Manufacturing Open-cell Open cell foams are manufactured by foundry or powder metallurgy. In the powder method, "space holders" are used; as their name suggests, they occupy the pore spaces and channels. In casting processes, foam is cast with an open-celled polyurethane foam skeleton. Closed-cell Foams are commonly made by injecting a gas or mixing a foaming agent into molten metal. Melts can be foamed by creating gas bubbles in the material. Normally, bubbles in molten metal are highly buoyant in the high-density liquid and rise quickly to the surface. This rise can be slowed by increasing the viscosity of the molten metal by adding ceramic powders or alloying elements to form stabilizing particles in the melt, or by other means. Metallic melts can be foamed in one of three ways: by injecting gas into the liquid metal from an external source; by causing gas formation in the liquid by admixing gas-releasing blowing agents with the molten metal; by causing the precipitation of gas that was previously dissolved in the molten metal. To stabilize the molten metal bubbles, high temperature foaming agents (nano- or micrometer- sized solid particles) are required. The size of the pores, or cells, is usually 1 to 8 mm. When foaming or blowing agents are used, they are mixed with the powdered metal before it is melted. This is the so-called "powder route" of foaming, and it is probably the most established (from an industrial standpoint). After metal (e.g. aluminium) powders and foaming agent (e.g. TiH2) have been mixed, they are compressed into a compact, solid precursor, which can be available in the form of a billet, a sheet, or a wire. Production of precursors