fs- and ns-laser processing of polydimethylsiloxane (PDMS) elastomer: Comparative study

Medical grade polydimethylsiloxane (PDMS) elastomer is a widely used biomaterial as encapsulation and/or as substrate insulator carrier for long term neural implants because of its remarkable properties. Femtosecond (λ = 263 and 527 nm) and nanosecond (266 and 532 nm) laser processing of PDMS-elastomer surface, in air, is investigated. The influence of different processing parameters, including laser wavelength, pulse duration, fluence, scanning speed and overlapping of the subsequent pulses, on the surface activation and the surface morphology are studied. High definition tracks and electrodes are produced. Remarkable alterations of the chemical composition and structural morphology of the ablated traces are observed in comparison with the native material. Raman spectra illustrate well-defined dependence of the chemical composition on the laser fluence, pulse duration, number of pulses and wavelength. An extra peak about ∼512-518 cm−1, assigned to crystalline silicon, is observed after ns- or visible fs-laser processing of the surface. In all cases, the intensities of SiOSi symmetric stretching at 488 cm−1, SiCH3 symmetric rocking at 685 cm−1, SiC symmetric stretching at 709 cm−1, CH3 asymmetric rocking + SiC asymmetric stretching at 787 cm−1, and CH3 symmetric rocking at 859 cm−1, modes strongly decrease. The laser processed areas are also analyzed by SEM and optical microscopy. Selective Pt or Ni metallization of the laser processed traces is produced successfully via electroless plating. The metallization process is not sensitive with respect to the time interval after the laser treatment. DC resistance is measured to be as low as 0.5 Ω mm−1. Our results show promising prospects with respect to use such a laser-based method for micro- or nano-fabrication of PDMS devices for MEMS and NEMS.