Lacunarity properties of nanophotonic materials based on poly(methyl methacrylate) for contact lenses

Abstract

The aim was to develop new materials that would, after appropriate machining processes, improve the surface roughness and wettability of contact lenses. The samples used in this investigation were standard rigid gas-permeable (RGP) SOLEKO contact lenses, made of poly-MMA-co-siloxy silane methacrylate material (known under the commercial name SP40 TM ), and its modifications by adding three nanomaterials: fullerene C60 (designated as SP40-A), fullerol C60(OH)24 (designated as SP40-B) and methformin hydroxylate fullerene C60(OH)12(OC4N5H10)12 (designated as SP40-C). Both atomic force microscopy (AFM) and magnetic force microscopy (MFM) were used to measure the topography and gradient of the magnetic field of the nanophotonic materials and the reference samples. According to the magnetic properties of all the materials yielded by MFM it can be concluded that adding fullerene and its derivatives certainly reduces the spectrum of the phase shifts angle by almost 50 %, which increases the paramagnetic characteristics of the nanophotonic material. The positive result of nanophotonic materials characterization is the fact that the roughness parameter values for all of these materials, are lower than those for the basic material. A surface lacunarity analysis, based on in-house procedures for determining the lacunarity value of contact lens surfaces, confirms the influence of surface topology on the tear film volume distribution and, consequently, the contact lens' surface lubrication. The presence of carbon nanomaterials, according to the surface roughness parameters, are improved for rigid gas-permeable (RGP) contact lenses made from nanophotonic polymer materials compared to those produced from the basic material. Keywords: fullerenes, polymer materials, surface roughness, atomic force microscopy, magnetic force microscopy Namen je bil razviti nov material, ki bi po ustrezni strojni obdelavi zmanj{al hrapavost povr{ine in omo~ljivost kontaktnih le~. Vzorci, uporabljeni v tej raziskavi so bile standardne toge, za plin prepustne (RGP) SOLEKO kontaktne le~e, narejene iz poli-MMA-ko-siloksi silan metakrilatnega materiala (s komercialnim imenom poznanega SP40 TM ) in njihove modifikacije z dodatkom treh nanomaterialov: fulerena C60 (ozna~enega kot SP40-A), fulerola C60(OH)24 (ozna~enega z SP40-B) in metformin hidroksilat fulerena C60(OH)12(OC4N5H10)12 (ozna~enega z SP40-C). Uporabljeni so bili: mikroskopija na atomsko silo (AFM), mikroskopija na magnetno silo (MFM) za merjenje topografije in gradient magnetnega polja nanofotonskih materialov in referen~nih vzorcev. Skladno z magnetnimi lastnostmi vseh materialov, dobljenih z MFM, je mogo~e zaklju~iti, da dodajanje fulerenov in njegovih izpeljank, mo~no zmanj{a spekter kotov faznega premika za skoraj 50 %, kar pove~a paramagnetne zna~ilnosti nanofotonskih materialov. Pozitivni rezultati karakterizacije nanofotonskih materialov so, da so vrednosti parametra hrapavosti pri vseh teh materialih ni`je kot pri osnovnem materialu. Analiza povr{inske razporeditve praznin, na osnovi...

Comparison of a Novel Ultrasonic Scaler Tip vs. Conventional Design on a Titanium Surface

“…Although originally developed for fractal objects, the method is more general and can be readily used to describe nonfractal and multifractal patterns, such as the roughness evaluation of SEM images. The lacunarity analysis was based on studies of Plotnick [27], Mandelbrot [29], and Voss [30], which proved applicability of lacunarity analysis on various machining surfaces [31,32,33]. Group Tests have been performed to analyse the differences between groups.…”

Characterization of surface roughness of new nanophotonic soft contact lenses using lacunarity and AFM method

“…The p-diagram presents topology with regular distributed lower hills and this type of curve was labeled as slanted p-diagram. This type of p-diagram corresponds to machined surface p-diagram from papers [41,42]. P-diagrams for SL38-A and SL38-B had four slopes and this type of curve was labeled as contorted.…”

“…None of the tested SCLs have irregular regions at their convex sides with height differences more than 615 nm. Thus, all irregularities at frontal surface will be smoothed by tear film when the contact lens is set on cornea [30,42]. The positive result of incorporating nanomaterials into basic material for SCL was better quality of the nanophotonic SCLs surfaces due to lower values of roughness parameters for all nanophotonic materials compared to those for basic material.…”

“…Atomic force microscopy (AFM) is a powerful technique that provides detailed surface characteristic information of contact lens materials [30][31][32][33][34][35][36]. Furthermore, the lacunarity analysis based on works of Mandelbrot [37], Voss [38] and Plotnick [39], regarding previous results [40][41][42], proves applicability of lacunarity analysis on various machining surfaces including lubrication aspect of surface functional behavior. Since Mandelbrot introduced the term lacunarity as a gappiness, the lacunarity application that is originally developed for further classification of fractals has become more generally and broadly applicable in natural sciences [43][44][45] as a very useful multi-scaled method for describing patterns of spatial dispersion.…”

“…Based on it, the in-house made procedures in Matlab software were developed. Procedures were applied for various surfaces' topography including tin metal surface [40] and RGP contact lens surfaces [41,42]. Gliding box was a window sliding systematically through the binary image which was obtained as a result of slicing surface topography image on levels.…”