Modulating surface stiffness of polydimethylsiloxane (PDMS) with kiloelectronvolt ion patterning

Abstract

This study is to investigate the modulated surface properties of polydimethylsiloxane (PDMS) with kiloelectronvolt ions. By irradiating the PDMS surface with a focused ion beam (FIB, keV Ga+), nano/microscale patterns of controlled stiffness can be fabricated with ion fluence ranging from 0.1–20 pC µm−2. The following nanoindentation measurements with an atomic force microscope (AFM) revealed that Young’s modulus increased exponentially with the increase of ion fluence and reached 2 GPa. The stiffening was found to be less significant with irradiation at a higher ion incident angle and lower accelerating voltage. Raman spectroscopy results also confirmed that disordering caused by cross-linking and hydrogen release occurred on the target PDMS surface. By modelling and experimenting on PDMS-Si3N4 bilayer structures, the volume reduction ratios of PDMS with ion beam and electron beam irradiation were estimated. The proposed site specific modulating method and understanding of detailed governing mechanisms will allow the tuning of the PDMS surface with great accuracy and flexibility towards future applications in tissue engineering and microfabrication.

The Functional Response of Mesenchymal Stem Cells to Electron‐Beam Patterned Elastomeric Surfaces Presenting Micrometer to Nanoscale Heterogeneous Rigidity

“…A similar increase in PDMS crosslinking, accompanied by increased rigidity, as a result of exposure to a Ga+ ion beam, was recently reported by Liu and Fu. [30] Ion beams are typically used to modify the structure of materials (i.e., by sputtering or by ion implantation), and in that work, the resultant mechanical change could be attributed to both modification of the PDMS polymer structure as well as the incorporation of Ga in the polymer. Similarly, a previous study by Bowen et al explored the effect of e-beam exposure on the mechanical properties of uncross linked PDMS with an aim to validating PDMS as a potential e-beam resist.…”

Adhesion and Mechanical Properties of PDMS-Based Materials Probed with AFM: A Review

“…Another situation is when only the small area should be studied, e.g. in vicinity of the filler particle or local area irradiated by focused electron [63] or ion beam [64]. Therefore, in certain cases it may be beneficial to probe the surface of PDMS with atomic force microscope (AFM).…”

Polynomial fitting techniques applied to opto-mechanical properties of PDMS Sylgard 184 for given curing parameters

“…Mechanical properties measurements of PDMS's samples are also detailed for predetermined synthesis parameters; relevant examples are the components´ratio of base mixture: catalyst (ratios varying from 2:1 to 33:1) [9,16,21,28], the curing temperature applied (from room temperature up to 310°C) [30,35], or the curing time (18 min to 48 h) [32,41]. Reports indicate that Young's modulus, compressive and shear moduli vary in the ranges of 12 kPa-3 GPa, 117.8 MPa-186.9 MPa and 100 kPa-3 MPa, respectively [14,18,22,35,37,42,43].…”

“…Recently, a report mentions the combination of PDMS with ZrO 2 providing a refractive index in the range of 1.39 to 1.69 depending on mixture concentration [41]. Furthermore, variations of refractive index have been detected with variation of curing temperature [42], or when PDMS is mixed with another diphenylsiloxane group [48] and when samples are subjected to tension, refractive index undergoes small variations [49].…”