Mechanical Engineer at an energy startup -- prototyping, integration, and testing

Mesodyne is a fast-growing, deep-tech startup revolutionizing portable power with our LightCell technology. Originating from MIT research, the LightCell uses thermophotovoltaics (TPV) to convert any fuel into quiet, reliable electricity. By delivering over a 10x improvement in endurance compared to batteries and bridging the gap with legacy engines, Mesodyne is unlocking crucial tactical advantages for defense, aerospace, and remote industrial applications. We are looking for an integration-focused Mechanical Engineer to design, build, and run the advanced experimental systems that allow our core thermophotovoltaic generator—the LightCell—to reach its target performance. Your playground is where thermodynamics, microfluidics, and vacuum physics meet the real world. You will take ownership of designing and building custom high-temperature thermal cycling setups, environmental simulation chambers, and the precision alignment fixtures required to integrate and test our photovoltaic and nanophotonic systems. Responsibilities Prototyping & Assembly: Work extensively with intricate physical assemblies. You will be hands‑on in the lab and machine shop bringing your ideas to life. Hands‑on Machining & Fabrication: Spend substantial time in our machine shop using manual mills, lathes, 3D printers, and hand tools to rapidly iterate, weld, and self‑fabricate your system designs. Able to work many different scales: from tabletop to micro. Design Advanced Testing Systems: Design custom, high‑fidelity mechanical test systems, experimental fluid loops, and automated thermal‑cycling frameworks to push our LightCells to their physical limits. Support System‑Level Integration: Work side‑by‑side with the R&D and pilot line assembly teams, troubleshooting complex mechanical, fluidic, and structural interface challenges. Characterize Prototype Performance: Set up test instrumentation, install sensors (thermocouples, pressure transducers, flow meters), and run physical validation experiments in the lab. Drive Design for Manufacturing and Assembly (DFM + DFA): Translate your hands‑on assembly and testing experiences back into actionable design feedback to the core R&D teams. Qualifications and skills Education & Experience: BS or MS in Mechanical Engineering. We are open to fresh graduates, recent Master's grads, or engineers with a few years of industry experience. Hands‑on Fabrication & Prototyping: A proven ability to build physical prototypes is required (strong extracurricular projects and student project teams count!). Machine shop experience (specifically manual mill and lathe) is a huge plus. Startup Mindset: You must be a "do-er." We are looking for someone who favors of rapid, hands‑on iteration. Communication: Strong written and verbal communication is required. Experience interfacing with vendors is a plus. CAD Proficiency: Good 3D CAD skills are required (we use Onshape, but general CAD competence is more important than platform-specific experience). Eagerness to Learn: A desire to continuously learn new skills on the job is required. You must be eager to learn a completely new set of materials and fabrication processes for high-temperature applications, as well as combustion engineering, vacuum technology, microfabrication, and other fields relevant to the LightCell. Location This position is based at our facility in Somerville, MA. #J-18808-Ljbffr Mesodyne