Fabrication and optical characterization of microstructures in poly(methylmethacrylate) and poly(dimethylsiloxane) using femtosecond pulses for photonic and microfluidic applications

Abstract

We fabricated several microstructures, such as buried gratings, surface gratings, surface microcraters, and microchannels, in bulk poly(methylmethacrylate) (PMMA) and poly(dimethylsiloxane) (PDMS) using the femtosecond (fs) direct writing technique. A methodical study of the diffraction efficiency (DE) of the achieved gratings was performed as a function of scanning speed, energy, and focal spot size in both PMMA and PDMS. An optimized set of writing parameters has been identified for achieving efficient gratings in both cases. The highest DE recorded in a PDMS grating was ∼10% and ∼34% in a PMMA grating obtained with an 0:65 NA (40X) objective with a single scan. Spectroscopic techniques, including Raman, UV-visible, electron spin resonance (ESR), and physical techniques, such as laser confocal and scanning electron microscopy (SEM), were employed to examine the fs laser-modified regions in an attempt to understand the mechanism responsible for physical changes at the focal volume. Raman spectra collected from the modified regions of PMMA indicated bond softening or stress-related mechanisms responsible for structural changes. We have also observed emission from the fs-modified regions of PMMA and PDMS. An ESR spectrum, recorded a few days after irradiation, from the fs laser-modified regions in PMMA did not reveal any signature of free radicals. However, fs-modified PDMS regions exhibited a single peak in the ESR signal. The probable rationale for the behavior of the ESR spectra in PMMA and PDMS are discussed in the light of free radical formation after fs irradiation. Microchannels within the bulk and surface of PMMA were achieved as well. Microcraters on the surfaces of PMMA and PDMS were also accomplished, and the variation of structure properties with diverse writing conditions has been studied.

Laser Surface Texturing of Polymers for Biomedical Applications

“…These features may be beneficial for the cell attachment and proliferation on PMMA modified surfaces, which make fs lasers a viable alternative to enhance biocompatibility. Deepak et al [73,75,106,107] also explored the utilization of Ti:Sapphire femtosecond lasers to produce microchannels in PMMA, and also in polystyrene (PS) for microfluidic applications (with potential biomedical applications). Peroxide-type free radicals where found along the laser treated areas.…”

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].…”

Conventional elastomers doped with benzophenone derivatives as effective media for all-optical fabrication of tunable diffraction elements

“…Comparing with alternative methods for the production of elastic gratings, e.g. using femtosecond pulses or ion beams, [34][35][36] the proposed approach is non-destructive and, consequently, diffraction elements possess higher optical quality, and moreover, the gratings of large area can be produced by a single-step exposure and also with much higher spatial resolution.…”