We investigate in this work the formulation of composite resistive pastes based on epoxy resins and graphite for micro-heater manufacturing via thick-film technology. The resistive paste is first screen-printed onto a printed circuit board (PCB) substrate, and then coated with expandable polydimethylsiloxane (PDMS), a composite based on an elastomeric matrix and expandable microspheres, resulting into one-shot thermal actuators allowing pumping and sealing in microfluidic devices. The resistive paste must therefore have controlled properties, such as rheology, resistivity and temperature stability. This paper details the formulation and characterization of suitable epoxy-graphite resistive composites, and the control of their properties through additives