Femtosecond laser-fabricated microstructures in bulk poly(methylmethacrylate) and poly(dimethylsiloxane) at 800 nm towards lab-on-a-chip applications

Abstract

Laser direct writing technique is employed to fabricate microstructures, including gratings (buried and surface) and two-dimensional photonic crystal-like structures, in bulk poly(methylmethacrylate) (PMMA) and poly(dimethylsiloxane) (PDMS) using ∼100 femtosecond (fs) pulses. The variation of structure size with different writing conditions (focussing, speed and energy) was investigated in detail. Diffraction efficiencies of the gratings were calculated and the changes in diffraction efficiency (DE) as a function of period, energy and scanning speed were evaluated. Highest diffraction efficiencies of 34% and 10%, for the first order, were obtained in PMMA and PDMS respectively. Heat treatment of these gratings demonstrated small improvement in the diffraction efficiency. Several applications resulting from these structures are discussed. Fs modification in PMMA and PDMS demonstrated emission when excited at a wavelength of 514 nm. We attempted to prepare buried waveguides in PMMA with higher refractive index at the core. We have successfully fabricated branched and curved structures in PMMA and PDMS finding impending applications in microfluidics.

Direct Writing in Polymers with Femtosecond Laser Pulses: Physics and Applications

“…We could clearly observe pseudo-green color from the fs laser modified regions which is an indication of emission. Similar results were obtained in case of other polymers also, details of which are summarized in references [35][36][37][38][39][40][41]. By combining the formation of micro-craters (which took place at high scan speed >3 mm/s and low energies of ~nJ) and the emission coming from the modified regions we establish the possibility of using the fluorescent micro-craters towards memory based applications.…”

High-Repetition-Rate Femtosecond Laser Processing of Acrylic Intra-Ocular Lenses

“…Among polymers, acrylic polymers have become one of the most popular materials due to its excellent properties, including optical transparency from the UV to the NIR spectral region, flexibility, elasticity, tunable mechanical properties, oxygen permeability, hydrophobicity, biocompatibility, biostability, durability and low cost [1,7,13]. This versatility has allowed acrylic polymers to be used as micro total analysis systems (µ-TAS), micro-electro-mechanical systems (MEMS), microfluidic channels, waveguides, as well as in numerous pharmaceutical and medical applications as neural implants or intraocular lenses [12][13][14][15][16][17][18][19][20][21].…”

“…In this technique, ultra-short laser pulses are tightly focused inside transparent materials inducing nonlinear absorption processes in the focal volume and leading to permanent weak local refractive index variations, formation of nano-voids, crystallization processes or even chemical transformations. This technique has been widely used to modify crystalline and glassy matrices as well as polymers to produce passive and active photonic devices, to create 2D/3D micro/nanostructures or to activate and functionalize the surface [15][16][17][18][19][20][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. Nevertheless, despite laser ablation of polymers is a well stablished process for industrial applications the contribution of the main mechanisms which may take part in the laser-polymer interaction process, i.e., photo-chemical and photo-thermal decomposition processes, are not clearly solved and the discussion is still controversial.…”

Femtosecond Laser Direct Writing and Spectroscopic Characterization of Microstructures, Craters, and Gratings in Bulk∕Thin Films of Polystyrene

“…We have fabricated such several structures in other polymers such as PMMA, PDMS, and PVA. In all these polymers we observed the formation of free radicals that exhibit emission upon fs laser irradiation and paramagnetic behavior (except for PVA) [10][11][12][13][14].…”