In future High Energy Physics detectors, the coverage of large surfaces with silicon pixel chip sensors poses a challenge for the sensors positioning, for their cooling, assembly, and interconnection. The use of a cooling substrate on which the sensors are glued is typically limited by the bulky and complicated hydraulic interconnection between adjacent substrates. In this research, a new type of cooling substrate is presented. Its design is based on microchannels, where additive manufacturing of plastic and ceramic materials has been considered an alternative to the current silicon etching process. A solution to the mechanical and hydraulic interconnection problem is achieved through a modular interlocking concept. Design optimisation was followed having identified three relevant parameters, plug-and-ply, interchangeability and sealing performance, which qualify the substrates interconnection and guaranty their correct positioning. This paper poses the bases to a new substrate category where modularity, re-workability and easy connectivity are the strong points. This concept could find applications also outside High Energy Physics experiments such as hardware cloud computing and medical detectors.