Microfluidic systems enable precise control of fluids at the microscale, yet most are designed without consideration of reuse, cleanability, or material sustainability, leading to short device lifetimes and increased waste. Among microfluidic systems, microdroplet generators represent a particularly stringent test case for reusability due to their narrow channels, sensitivity to surface contamination, and widespread use across chemical, biological, and materials processing. Here, we present a scalable and cost-effective microfluidic platform designed explicitly for reuse, demonstrated using a flow-focusing microdroplet generator as a proof of concept. Mass-manufactured microchannel networks are integrated into a reusable housing composed of mechanically compressed polycarbonate and silicone layers, enabling uniform sealing, robust leak-free operation, and rapid disassembly for cleaning. The modular housing supports component-level replacement rather than full device disposal and allows individual microchannel networks to be reused across multiple operational cycles with minimal impact on performance. To demonstrate recoverability under conditions that would conventionally necessitate device disposal, we examine droplet generation using a high-fouling agar dispersed phase during controlled cooling to the point of gelation, where blockages can be readily cleared and the system reused. These results establish a reusable, mass-manufacturable microfluidic platform that applies circular design principles to microscale fluid handling.

This study presents a sustainable surface engineering approach aimed at extending the service life and enabling the restoration of worn 42Cr4 steel components within a circular manufacturing framework. Wear-induced surface degradation is a primary failure mechanism in mechanical systems, leading to increased maintenance costs, energy losses, and excessive consumption of raw materials. In this work, the surface of 42Cr4 steel was modified by Tungsten Inert Gas (TIG) surface remelting assisted by a high-frequency magnetic field. Unlike conventional TIG treatments and post-process magnetic field applications, the proposed method applies the magnetic field in situ during remelting, enabling real-time control of molten pool dynamics. The tribological performance of the treated specimens was evaluated using a ball-on-disc configuration under paraffin lubrication, and friction and wear behavior were systematically quantified. The results indicate that magnetically assisted TIG remelting significantly enhances surface hardness and tribological performance. These improvements are attributed to intensified electromagnetic stirring within the molten pool, which promotes grain refinement, reduces porosity, and ensures a uniform distribution of alloying elements in the remelted layer. As a result, the treated surfaces exhibit improved load-bearing capacity and enhanced resistance to wear under lubricated sliding conditions. From an application perspective, the proposed hybrid process provides an effective and scalable solution for component repair and surface regeneration. Restoring functional surfaces without full component replacement offers clear environmental and economic advantages. In addition, localized surface treatment significantly reduces material consumption and energy demand, thereby supporting resource-efficient and circular economy strategies.