Optimization of the replica molding process of PDMS using pennate diatoms

Abstract

Biomimetic fabrication of nanostructured materials has recently attracted the attention of researchers as a cost-effective and easily applicable method of nanotexturing. Different techniques and materials have been used in order to replicate natural patterns, among which polydimethylsiloxane (PDMS Sylgard 184 R ) was recently used to replicate the micro-and nanoscale patterns from centric diatoms. In this paper, we test the reproducibility and precision of this approach using various morphologically different diatom species trying to optimize the molding parameters. The optimization process is focused on immobilization of diatoms on the glass support, which serves as a master for templating, as well as on the parameters of PDMS fabrication such as the ratio of the curing agent and elastomer, use of vacuum, curing time and temperature. The results indicate that higher ratios of curing agent and elastomer, longer curing time and lower temperature are the most favorable conditions to obtain negative diatom replicas of good quality with features of 50 nm. Although this method can give very precise results producing high-resolution molds with all micro-and nanostructures replicated, we revealed some limitations regarding the size and morphology of the species used. These results indicate that large round and flat diatom species seem to be more suitable for the cast molding.

Diatoms: a biotemplating approach to fabricating drug delivery reservoirs

“…Similarly, other diatom replicas have been produced by Sandhage et al via oxidation-reduction gas/solid displacement reactions to form various structural replicas composed of magnesium oxide, zirconium dioxide, titanium dioxide and silicon [45][46][47][48][49]. Furthermore, there are reports of successful generation of a negative replica of the diatom using an imprinting method with polydimethylsiloxane, which can act as a template to produce positive structural replicas in a wide range of materials [50,51]. However, while these inorganic methods have shown efficacy in replicating the diatom skeleton, there is currently a severe lack of organic replication techniques (i.e., oil-in-water emulsion, sol--gel synthesis, layer-by-layer assembly, etc.)…”

On the 3D reconstruction of diatom frustules: a novel method, applications, and limitations

“…Some of its advantages are imaging with minimum sample preparation (a conductive layer is not required), ability to measure structural and micromechanical properties (hardness, adhesivity, and elasticity), and the potential of imaging live diatoms in aqueous medium (Losic et al 2007). Hlúbiková et al (2012), for example, used AFM to characterize the topography and the distance between pores in diatom valves and PDMS replicas. Also Losic et al (2007) used AFM to characterize diatom topography.…”

“…The diatom frustule can also be exploited for several technical applications, such as the direct use of silica structure, biomimicry of silification routes, surface functionalization (i.e., chemical attachment of different molecules on the surface), preparation of nanocomposites and as structures for templating (Townley 2011). These novel applications, summarized by Gordon et al (2008), are already attracting the attention of nanotechnologists (Parkinson and Gordon 1999;Cai et al 2006;Yu et al 2010;Nassif and Livage 2011), and several methods have been proposed to replicate the 3D nanostructure of centric (Losic et al 2005(Losic et al , 2006(Losic et al , 2007 and pennate (Hlúbiková et al 2012) diatoms.…”

Large-scale solvent-swelling-based amplification of microstructured sharkskin

“…Natural evolution provides sophisticated natural surface treasures with the tremendous function of inspiring creative design, such as the drag reduction or antifouling properties of sharkskin and the hydrophobicity of lotuses [1][2][3][4][5]. Considerable research has focused on fabricating microscale/nanoscale biomimetic surface structures [6][7][8][9][10][11][12]. For example, Brennan et al creatively fabricated an impressive biomimetic structure (Sharklet) for preventing the growth of cells on certain surfaces, such as on the bottom of 1 Author to whom any correspondence should be addressed.…”

“…Simplifying the natural surface morphology usually diminishes the surface function. To resolve this problem, a 1:1 accurate bioreplication forming technique that directly uses the natural surface as the molding template has been proposed [9,14,15]. Natural surfaces function optimally only in their living environment; staying far from the living environment impairs or even reverses the function.…”