HotEmbossing

Hot embossing is a replication process that transfers patterns from a rigid mold into a thermoplastic substrate by heating the material above its glass transition or melting temperature and applying pressure to imprint the pattern. The embossed part is then cooled below Tg and the mold is separated. This technique is used for films, sheets, and micro-scale structures in microfluidics and optics.

Equipment typically includes a hot embossing press with heated platens, a patterned mold (often made of steel, nickel, or silicon), and a thermoplastic substrate such as PET, PMMA, PC, or COC. The substrate is heated above Tg or Tm, the mold presses the pattern into the surface with a controlled dwell time, and vacuum can be used to reduce air pockets. The stack is cooled and demolded. Fidelity depends on mold quality, polymer rheology, cooling rate, and surface finish.

Molds are created from masters by electroforming, lithography, or machining. Substrates include PET, PC, PMMA, polystyrene, and fluoropolymers, chosen for Tg, hardness, and optical properties. Feature sizes typically range from micrometers to millimeters; with optimized conditions, sub-micron features may be possible in specialized setups.

Applications span optical films and micro-optics, microfluidic channels and membranes, textured or decorative surfaces, security features in packaging, and patterned electronics or sensors. Hot embossing can be paired with thermal bonding to seal microchannels or assemble multi-layer devices.

Advantages include high-resolution pattern transfer and suitability for large-area and high-volume production, often in roll-to-roll formats. Limitations involve precise temperature and pressure control, potential residual stresses or deformation, mold wear, and restriction to thermoplastics with appropriate Tg or Tm.