Abstract: The present disclosure relates to a conductive trace precursor composition comprising a metal salt; 3 to 15 weight % of a reducing solvent selected from a lactam and/or a polyol, and water. Where the reducing solvent is 2-pyrrolidinone, the 2-pyrrolidinone is not present in an amount of 5 weight % or in an amount of 7.5 weight % of the conductive trace precursor composition.

Abstract: The present disclosure relates to a method of 3D printing a 3D printed object. The 5 method comprises printing a layer of a build material composition comprising a solution of a metal salt and a liquid carrier. An interconnected metal network is formed by reducing the metal salt in the printed build material composition. A further layer of the build material composition is printed over the interconnected metal network, and the metal salt in the further layer is reduced to form a further 10 interconnected metal network over the underlying interconnected metal network to provide a porous structure to the 3D printed object. By layering and joining interconnected metal networks one on top of another, porous regions may be constructed within the 3D printed part.