Proof of concept

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Microfluidic and millifluidic systems are increasingly used for chemical and biological analysis. Thermoplastic polymers offer a practical alternative to glass and silicon. They are inexpensive, easy to shape, and suitable for disposable devices. However, most polymer microfluidic chips are still produced in two steps: machining the channels, then bonding a cover plate. This workflow increases alignment constraints, exposes open channels to contamination, and lengthens production time. This study presents a one-step method based on transmission laser welding (TLW) applied to closed-cell thermoplastic foams. The laser heats and collapses the foam locally, causing the cell walls to fuse and form a channel while welding a transparent cover at the same time. The process creates a sealed microchannel without moving the parts between steps. We examine the feasibility of this method and study how laser output power affects channel dimensions. The approach also enables the creation of X and Y junctions by using several fast passes to control melting at the intersections. The channels obtained show smooth internal walls and a near-cylindrical cross-section. Their size can be adjusted through the laser parameters. This method offers a simple and clean way to prototype polymer millifluidic or microfluidic devices.