Disclosed herein are a variety of microfluidic devices and solid, typically electrically conductive devices that can be formed using such devices as molds. In certain embodiments, the devices that are formed comprise conductive pathways formed by solidifying a liquid metal present in one or more microfluidic channels (such devices hereinafter referred to as “microsolidic” devices). In certain such devices, in which electrical connections can be formed and/or reformed between regions in a microfluidic structure; in some cases, the devices/circuits formed may be flexible and/or involve flexible electrical components. In certain embodiments, the solid metal wires/conductive pathways formed in microfluidic channel(s) may remain contained within the microfluidic structure. In certain such embodiments, the conductive pathways formed may be located in proximity to other microfluidic channel(s) of the structure that carry flowing fluid, such that the conductive pathway can create energy (e.g. electromagnetic and/or thermal energy) that interacts withy and/or affects the flowing fluid and/or a component contained therein or carried thereby. In other embodiments, a microsolidic structure may be removed from a microfluidic mold to form a stand-alone structure. In certain embodiments, the solid metal structures formed may interact with light energy incident upon a structure or may be used to fabricate a light-weight electrode. Another aspect of the invention relates to the formation of self-assembled structures that may comprise these electrically conductive pathways/connections.