**6. Results**

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Picture of surface that is taken by classical optical microscope is based on electromagnetic property of light, while OMF is based on difference between diffuse white light (like that of daily light) and reflected polarized light. Reflected polarized light is produced when source of diffuse light irradiates the surface of matter under certain angle (Brewster's angle, see figure 5). Each type of matter has different angle value of light polarization. Since reflected polarized light contains electrical component of light-matter interaction, taking the difference between white light (electromagnetic) and reflected polarized light (electrical) yields magnetic properties of matter based on light-matter interaction. Because such measurement can identify the conformational state and change in tissue on molecular level we named this method the

Fig. 5. Incident white light can give different information about thin layer of matter (surface) properties of sample depending on the angle of light incidence. When the incident white light is diffuse, the reflected white light is then composed of electrical and magnetic

components, whereas diffuse incident light that is inclined under certain angle will produce reflected light which contains only electrical component of light. For each type of matter there is a characteristic angle of incidence (Bandi´c et al., 2002) for obtaining the appropriate

We used digital images in RGB (R-red, G-green, B-blue) system in our analysis, therefore we chose basic pixel data in red and blue channels for white diffuse light (W) and reflected polarized white light (P). Algorithm for data analysis is based on chromaticity diagram called "Maxwell's triangle"and spectral convolution operation according to ratio of (R-B)& (W-P) (Koruga et al., 2008). The abbreviated designation means that Red minus Blue wavelength of White light and reflected Polarized light are used in spectral convolution algorithm to calculate data for opto-magnetic fingerprint of matter. Therefore, method and algorithm for creating a unique spectral fingerprint are based on the convolution of RGB color channel spectral plots generated from digital images that have captured single and multi-wavelength light-matter interaction (Koruga et al., 2008). Preparation of digital pictures for OMF was made by usage of dermoscopic imaging device (MySkin, USA) that has previously been successfully used in biophysical skin characterization (skin photo type,

The final purpose of our research in applying OMF is the construction of quality control method which would be purely optical and able to, on the basis of digital image analysis and processing, detect both the morphology and functionality parameters in a quicker and more accurate manner. In order to do so we need to construct quantification parameters but, in this stage of research, primarily integrate results from morphological research and opto-magnetic

opto-magnetic fingerprint of matter (OMF).

reflected polarized light.

properties.

moisture, conductivity, etc) (Bandi´c et al., 2002).

### **6.1 Topography measurement using Atomic Force Microscope – AFM**

Topography measurements were routinely conducted in tapping mode in ambient air using uniform scanning surface of 5 × 5*μm*. The CL inner surface has been examined as shown in figure 6. The curvature of the surface prevents the AFM probe to reach its center, unless the sample is destroyed. Nevertheless, a good approach was able to the area that is approximately on the half distance of CLs radii. A total of four points were selected for scanning on each CL in two perpendicular directions. In each point two scans were conducted: one with 60 × 60*μm* surface size and the other with the 5 × 5*μm* surface size. The purpose of larger area scans were to confirm the uniform character of surface morphology while smaller scans were further analysed by fractal analysis.

Fig. 6. Experimental setup used in AFM imaging of CL surfaces.

### **6.2 Phase-contrasted AFM**

Phase contrast images are combined with topography images since these two measurements are performed simultaneously. Topography image yields information about surface shape and relative positions and dimensions. Phase contrast image enrichens that information by differentiating between different force gradients which in turn point to different conformational states of polymers, under the assumption that material constituents are homogenously distributed throughout the sample. Phase-Contrasted image of the CL is shown on figure 7.

### **6.3 Magnetic force microscopy**

The AFM/MFM measurements display the features of surface morphology and magnetism on the nanometer scale and are shown on two images in figure 8. Since the sensitivity of

Fig. 7. Phase-Contrasted Atomic Force Microscopy: scan size is 5 × 5*μm*. Left: topography image with maximum profile height of 150.9 nm. Right: phase contrasted image for the same portion of the sample that is shown on the left image. Phase contrast image shows granular inhomogeneity in the sample that is synthesized as homogenous (on the nano-scale). The inhomogeneities may originate only as a consequence of processing, showing that certain parts of surface have polymers with altered conformation states, thereby expressing different slope of intermolecular interactions.

forces measured by cantilever go well below nanonewton range, this means that we are able to record paramagnetic and diamagnetic behavior of material. The brighter image areas mark more highly responsive magnetic behavior or paramagnetic areas while than darker areas correspond to diamagnetic areas of the sample.

Fig. 8. Magnetic Force Microscopy: scan size is 5 × 5*μm*. Left: topography image with maximum profile height of 150.9 nm. Right: the magnetic force gradient image of the same area. This image shows changes in magnetic force gradient, exhibiting that magnetic behaviour exist on the para- and diamagnetic levels and that they are inhomogenous in our samples (that are chemically homogenous).

### **6.4 Opto-magnetic fingerprint and UV-vis spectroscopy**

Digital images of contact lenses were analyzed in terms of their separate color channels (red, blue and green color components) and subsequently processed by spectral convolution algorithm to give the final result – OMF diagram – which shows the intensity values of paramagnetic (positive) and diamagnetic (negative), properties in comparison to wavelength 12 Will-be-set-by-IN-TECH

Fig. 7. Phase-Contrasted Atomic Force Microscopy: scan size is 5 × 5*μm*. Left: topography image with maximum profile height of 150.9 nm. Right: phase contrasted image for the same portion of the sample that is shown on the left image. Phase contrast image shows granular inhomogeneity in the sample that is synthesized as homogenous (on the nano-scale). The inhomogeneities may originate only as a consequence of processing, showing that certain parts of surface have polymers with altered conformation states, thereby expressing different

forces measured by cantilever go well below nanonewton range, this means that we are able to record paramagnetic and diamagnetic behavior of material. The brighter image areas mark more highly responsive magnetic behavior or paramagnetic areas while than darker areas

Fig. 8. Magnetic Force Microscopy: scan size is 5 × 5*μm*. Left: topography image with maximum profile height of 150.9 nm. Right: the magnetic force gradient image of the same area. This image shows changes in magnetic force gradient, exhibiting that magnetic behaviour exist on the para- and diamagnetic levels and that they are inhomogenous in our

Digital images of contact lenses were analyzed in terms of their separate color channels (red, blue and green color components) and subsequently processed by spectral convolution algorithm to give the final result – OMF diagram – which shows the intensity values of paramagnetic (positive) and diamagnetic (negative), properties in comparison to wavelength

slope of intermolecular interactions.

correspond to diamagnetic areas of the sample.

samples (that are chemically homogenous).

**6.4 Opto-magnetic fingerprint and UV-vis spectroscopy**

difference. The diagrams on figure 9 show comparison of OMF diagrams with classical UV-Vis-NIR for two samples with different surface qualities.

Fig. 9. Opto-Magnetic Fingerprint: comparisons of OMF (upper two diagrams) and UV-Vis spectras (lower two diagrams) for differently surface-treated contact lenses that were produced from the same, standard, material. The characteristic diagrams for lathe processed (left) and polished (right) CL surfaces. UV-Vis spectras show almost identical patterns of absorption while OMF diagrams show visible differences in the wavelength difference range between 100 and 150 nm. These differences are due to different processing and can be quantized by ratio of paramagnetic to diamagnetic properties.

The OMF diagrams show the distribution of energies of reflected light that are distributed over a wavelength difference range. We can observe a qualitatively same pattern, except in the subregion between 100–150 nm, which shows variations in wavelengths and intensities. These diagrams show very high sensitivity of OMF imaging and software analysis, which is the exact purpose this method was intended to achieve.

Moreover, we have tested the OMF response for two inner surfaces of RGP CLs of type *BostonTM* with respect to changes in the surface qualities. One pair of lenses was processed differently (one was while the other was not polished) while the other pair was processed identically (same polishing times).

### **6.5 Fractal analysis of contact lenses' roughness profiles**

Currently we have no clear answer to the question what surface standard parameter should be used for critical limit determination. The result of the study, reported in (Bruinsma et al., 2003), also confirms the need for quantitatively establishing the replacement schedule of RGP CL. The water contact angle, percentage of elemental surface composition and deposit rate of bacteria was related to standard average roughness parameter *Ra*. It was stated in (Kim et al., 2002) that surface roughness was the most influential lens surface property after 10 days of wear.

Our research has utilized fractal analysis of roughness profiles to quantify the texture properties of CL inner surface. Standard surface parameters (roughness descriptors) fails

Fig. 10. Opto-Magnetic Fingerprint diagrams. Image on the left: overlapped OMF diagrams of two differently processed CLs that show different behaviour in the wavelength difference range of 130–150nm and sensitivity to changes in surface qualities. Image on the right: overlapped OMF diagrams of two identically processed CLs that show minor change in diagrams and surface qualities.

to describe functional nature of the surface. Moreover, use of more than one roughness parameter exhibits more shortcomings. This is mainly due to the partial information contained in each descriptor.

Fractal analysis of biomedical surface topography is influenced by growing interest in biomaterials surface technology. Fractal geometry provides a useful tool for the analysis of complex and irregular structures such as biomedical surface topography based on image analysis methods that consider an image as a 3D surface.

Fractal dimension calculation is based on "slit-island"and "skyscrapers"methods that were proposed in (Bojovi´c, 2008). This method stipulates that surface recording data is obtained as an image, by using scanning probe microscope. Fractal analysis consists of the following steps:


$$A(\varepsilon) = \sum \varepsilon^2 + \sum \varepsilon [|z(\mathbf{x}, y) - z(\mathbf{x} + 1, y)| + |z(\mathbf{x}, y) - z(\mathbf{x}, y + 1)|] \tag{2}$$

3. According to (Bojovi´c, 2008), the fractal dimension D can be generated from relation 3 for Hausdorff-Besicovitch dimension where N(*ε*) is the number of self-similar structures of linear size *ε* needed to cover the entire structure. Number N(*ε*) can be represented as shown in 4 and used for the area vs. square size relationship 5 resulting in equation 6. Using of logarithmic rules on relation 6 result in a linear equation, expressed as 7. Fractal dimension D is obtained as the slope of fitted line, determined by using relation 7 in the custom-made procedure for calculation 11.

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Fig. 10. Opto-Magnetic Fingerprint diagrams. Image on the left: overlapped OMF diagrams of two differently processed CLs that show different behaviour in the wavelength difference range of 130–150nm and sensitivity to changes in surface qualities. Image on the right: overlapped OMF diagrams of two identically processed CLs that show minor change in

to describe functional nature of the surface. Moreover, use of more than one roughness parameter exhibits more shortcomings. This is mainly due to the partial information

Fractal analysis of biomedical surface topography is influenced by growing interest in biomaterials surface technology. Fractal geometry provides a useful tool for the analysis of complex and irregular structures such as biomedical surface topography based on image

Fractal dimension calculation is based on "slit-island"and "skyscrapers"methods that were proposed in (Bojovi´c, 2008). This method stipulates that surface recording data is obtained as an image, by using scanning probe microscope. Fractal analysis consists of the following

1. Conversion of AFM image to numerical data in the form of matrix with subsequent conversion of matrix with 256 levels to matrixs with 216 levels of intensity [0, 65535] needed

2. Calculation of image surface area by well known method called "skyscrapers"method. This method approximates surface area of image A with sum of top squares that represent skyscrapers' roofs and the sum of exposed lateral sides of skyscrapers, according to (Chappard et al., 1998). The roof of skyscrapers are increased subsequently by grouping of adjacent pixel grouping. Thus, the intensities of grey scale are averaged. The square size *ε*

3. According to (Bojovi´c, 2008), the fractal dimension D can be generated from relation 3 for Hausdorff-Besicovitch dimension where N(*ε*) is the number of self-similar structures of linear size *ε* needed to cover the entire structure. Number N(*ε*) can be represented as shown in 4 and used for the area vs. square size relationship 5 resulting in equation 6. Using of logarithmic rules on relation 6 result in a linear equation, expressed as 7. Fractal dimension D is obtained as the slope of fitted line, determined by using relation 7 in the

<sup>2</sup> <sup>+</sup> ∑*ε*[|*z*(*x*, *<sup>y</sup>*) <sup>−</sup> *<sup>z</sup>*(*<sup>x</sup>* <sup>+</sup> 1, *<sup>y</sup>*)<sup>|</sup> <sup>+</sup> <sup>|</sup>*z*(*x*, *<sup>y</sup>*) <sup>−</sup> *<sup>z</sup>*(*x*, *<sup>y</sup>* <sup>+</sup> <sup>1</sup>)|] (2)

diagrams and surface qualities.

contained in each descriptor.

for further calculations.

is 2*<sup>n</sup>* and the formula is as follows:

*A*(*ε*) = ∑*ε*

steps:

analysis methods that consider an image as a 3D surface.

$$D = \lim\_{\varepsilon \to \infty} \frac{\log N(\varepsilon)}{\log \frac{1}{\varepsilon}} \tag{3}$$

$$N(\varepsilon) = c\_1 \varepsilon^{-D} \tag{4}$$

$$A(\varepsilon) = N(\varepsilon)\varepsilon^2 \tag{5}$$

$$A(\varepsilon) = c\_1 \varepsilon^{2-D\_s} \tag{6}$$

$$
\log A = (2 - D\_s) \log \varepsilon + \varepsilon \tag{7}
$$


Fig. 11. The log-log graph of image area vs. square size for two CLs. Samples are two RGP CLs made of ML 92 Siflufocon A. The first lens (CL5) was worn for about 3 years while the second lens was worn over a period of more than 5 years (CL1). We can see that fractal dimensions can easily distinguish between two levels of surface roughness created by wear of CL surface.

The procedure is schematically presented in the figure 12 .

Mandelbrot claimed that nature has a fractal face and scholars proved that engineering surfaces have fractal geometry. Compilations of a man-made surface with a tear component on it also show fractal behaviour, proven by power law of area vs. scale relationship. According to (Russ, 1998) a surface with fractal dimension 2.5 would be the optimum as an engineering surface for certain applications.

The fractal dimension generated by skyscrapers method for topography image offers additional and appropriate information about surface roughness. Fractal dimension, as roughness parameter, adequately explains surface functional behaviour. Fractal dimension for new contact lens surface could be an adequate behaviour prediction parameter.

### **7. Discussion**

By performing UV-Vis spectroscopy we have shown that UV-Vis spectra do not change with respect to changes in surface quality (see figure 9) because they measure bulk response of

Fig. 12. Diagram of steps involved in fractal analysis of AFM scans.

contact lense materials while opto-magnetic diagrams (OMF) displayed informations that are more sensitive to changes in near-surface properties of material (which are primarily altered during contact lense production). OMF has shown as method that can detect very sensitive to differences in topographical features of contact lenses.

Since, conformation changes in near-surface polymer molecules generate quantum effects they might influence magnetic properties as well. Because of that, we have investigated near-surface regions of contact lenses samples from magnetic and optomagnetic point of view to see whether is there exist a measurable difference in surface magnetic and optical properties. Our aim was to explore the relationship between surface morphology on one side and optical and magnetic properties on the other side.

Measurements on the nano-scale have shown that phase-contrasted atomic force microscopy (PC AFM) and magnetic force microscopy imaging carry additional information that is not contained in morphology scans. However, PC AFM and MFM data need to be integrated with results of OMF in order to obtain quick quantitative assessment of changes in nano- and pico-magnetism that can be related to change in surface structure and its optical properties. Elucidating the origin of these kinds of surface behavior requires further investigations and inclusion of other polishing process parameters on one side and quantitative MFM measurements on the other side. It is our opinion that this kind of analysis will be able to precisely determine parameters of final shape and performance of CL surface.

Since conformation states of RGP CL surface determine paramagnetic diamagnetic properties that can be detected by novel OMF technique, we consider the OMF method and molecular level approach to investigation of optical properties of CL quality as a very promising field for both basic research and technology, with direct influence on application in biomedicine.

New methods of investigation require novel data processing techniques. Fractal analysis has offered more sophisticated tool that, on the basis of nano-scale precision information, generates finer estimate of surface roughness quality.

### **8. Conclusion**

Light has influence on brain activity with very complex pathway (see figure 13). Since light is composed of electrical and magnetic spectra it is very important to know how light interact with contact lenses. These aspects of brain functioning have been thoroughly investigated; 16 Will-be-set-by-IN-TECH

contact lense materials while opto-magnetic diagrams (OMF) displayed informations that are more sensitive to changes in near-surface properties of material (which are primarily altered during contact lense production). OMF has shown as method that can detect very sensitive to

Since, conformation changes in near-surface polymer molecules generate quantum effects they might influence magnetic properties as well. Because of that, we have investigated near-surface regions of contact lenses samples from magnetic and optomagnetic point of view to see whether is there exist a measurable difference in surface magnetic and optical properties. Our aim was to explore the relationship between surface morphology on one side

Measurements on the nano-scale have shown that phase-contrasted atomic force microscopy (PC AFM) and magnetic force microscopy imaging carry additional information that is not contained in morphology scans. However, PC AFM and MFM data need to be integrated with results of OMF in order to obtain quick quantitative assessment of changes in nano- and pico-magnetism that can be related to change in surface structure and its optical properties. Elucidating the origin of these kinds of surface behavior requires further investigations and inclusion of other polishing process parameters on one side and quantitative MFM measurements on the other side. It is our opinion that this kind of analysis will be able to

Since conformation states of RGP CL surface determine paramagnetic diamagnetic properties that can be detected by novel OMF technique, we consider the OMF method and molecular level approach to investigation of optical properties of CL quality as a very promising field for both basic research and technology, with direct influence on application in biomedicine. New methods of investigation require novel data processing techniques. Fractal analysis has offered more sophisticated tool that, on the basis of nano-scale precision information,

Light has influence on brain activity with very complex pathway (see figure 13). Since light is composed of electrical and magnetic spectra it is very important to know how light interact with contact lenses. These aspects of brain functioning have been thoroughly investigated;

precisely determine parameters of final shape and performance of CL surface.

Fig. 12. Diagram of steps involved in fractal analysis of AFM scans.

differences in topographical features of contact lenses.

and optical and magnetic properties on the other side.

generates finer estimate of surface roughness quality.

**8. Conclusion**

vast amount of informations is available but the most subtle biophysical aspects are still not completely understood.

Fig. 13. Nerve pathways from the eyes to the brain goes not only to the visual cortex, but also to deeper brain areas, concerned with neurotransmiters, neurohormones, emotions, etc.

Visual perception is the ability to interpret information from information contained in visible light that reaches the eye. The act of seeing starts when the lens of the eye focuses an image of its surroundings onto a light-sensitive membrane in the back of the eye, called the retina. Since visible light is composed of electrical and magnetic spectra, which have different influence on brain activity (EEG and MEG signals, see figure 14), we investigated magnetic property of contact lenses, as optical material, which have influence on electrical and magnetic light signals properties.

Fig. 14. Brain activity (EEG and MEG) under light influence when eyes are open and closed.

The findings of our measurements enable us to couple optical and magnetic behavior analysis in determination of mechanical properties of surfaces. The dynamical structure of CL materials and its behavior under dynamical mechanical and thermal load is expressed in changes in paramagnetic/diamagnetic behavior. Our results show that these changes are measurable and can be quantified by a simple, quick and accurate method of OMF.

We believe that this combination of intertwining methods could yield an optimal approach towards investigating phenomena in material synthesis and its behavior under mechanical and thermal stress that is still not well understood. The grounds for our propositions are proven relationships between optical, magnetic and mechanical properties of matter. It is our intention to further improve the application of all three used methods and customize their parameters in order to combine them into a new device for opto-magneto-spectroscopic characterization of matter.

Furthermore, our future research will involve nanomaterials as a new doping material influencing CL physical properties such as light transmission, these changes will be investigated by by UV-Vis-NIR spectroscopy as well as optomagnetism. The potential application of nanomaterials might bring significant biophysically based implications for contact lenses industry, biomedical application industry and applied optical science.

### **9. References**

