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Results of the experiments which show unusual properties of jelly-like soap-gelatin films and their strength, longevity, use for laser tracks study and other optical applications are discussed.
Теги: laser solitons light pressure thib films optical properties давление света лазерные солитоны оптические свойства тонких пленок
In continuing the studies of laser spatial solitons (tracks) generated by the pressure of light in soap films [1], we tested films with various composition. Besides the simple unsupported free soap films, soap-gelatin films with the addition of glycerin having many unusual properties were used in the experiments, which allowed us to decelerate flings of laser tracks in them and clarify the nature of dancing inconstancies in their position [2]. Ability of such films in enclosed volumes to retain their form and optical properties for a long time (for one year already) not changing them turned out to be very useful for the study of tracks and it is very convenient for the repeated check of track properties and analysis of influence of changing environmental conditions on them. It was shown that in such film narrow tracks are formed also with wide-band white light. Single track in the soap-gelatin film for the first time allowed demonstrating the influence of modulation of exciting laser light on it up to the track dispersion [2]. These works are the continuation of historical works of P.N. Lebedev concerning the visual demonstration of the pressure action of light.
Properties of the gelatin films in enclosed volume as well as in air when water evaporates from them turned out to be interesting. Experiments with such films in air not connected with laser tracks directly turned out to be interesting due to some other peculiarities. As it is known, the standard soap bubbles in air usually break, while the transparent rainbow bubbles formed from such gelatin film after drying up do not break but remain in the initial form for weeks (Fig. 1), in other words they become attractive items, decorations and toys for children. As opposed to the known soap polymerized films which set to the solid state in the air and after drying up lose their elasticity, shrink and blow off after 24 hours, gelatin bubbles retain elasticity even without water and after 24 hours can be still noticeably blown and increase in diameter. It shows that thin gelatin film is elastic and poorly permeable for air.
Dried material of films can be dissolved again in small quantity of water and re-used in experiments. The thinness of walls, elasticity and simplicity of obtainment dif-ferentiate the soap-gelatin bubbles from well-known gelatin empty balls with thick walls which are made on the blown rubber balloons using the labor-intensive method of papier-mache.
The distinguished high elasticity, which is not typical for common gelatin- jelly, is caused by the additions of glycerin and soap to it. In such solution a new rubber-like structure with linkage of long molecules of gelatin and glycerin, which was mentioned above, occurs [3]. And addition of a specially selected soap gives opportunity to ob-tain thin films from the solution and strange elasticity (which will be described below in detail) of such films. Observed unusual transformation of jelly-like mass into the "tight and soft" material deserves attention of specialists in this field [4].
Optical properties of the thin gelatin film draw attention as well. Since the initial and dried soap film have smooth surface, even with its partial reflection it can serve as a mirror, radius, focal distance of which can be changed within wide ranges. The examples of such mirror reflections from the film are shown in Fig. 2. But besides the reflectivity, one more wonderful property of gelatin film was discovered.
Judging by the color, film thickness is about 5-10 μm. We can judge on strange and, one can say, even unexpected strength of such a little bit dried film by the load it can bear (Fig. 3, 4). While for regular water soap films the permissible load is deter-mined by its surface tension (of two surfaces) and it is about 0.07 g/cm, here, as we can see, gelatin film without break bears the load of about 1 g/cm which is obviously by an order of magnitude higher and cannot be provided by the simple surface tension. It requires the tension inside of the film, as well.
When the load is removed, the deformed film completely restores its initial form in seconds. In essence, the film turns out to be an example of unusual transparent-specular rubber with attractive capabilities of its use for various optical applications.
For example, load on the film can be in the form of liquid which does not interact with the film and while accumulating in the film center turns into liquid lens with var-iable focal distance (if we change air pressure under the film) Fig. 4. The used poured liquid can be a polymerized one as epoxy resin and after solidification on the film it -l turns into quite good and, which is important to note, aspheric transparent lens with optically smooth surfaces and small focal distance without any additional treatment (Fig. 5-7). Specialists who know the challenges connected with the production of as-pheric optics can duly appreciate such gift of nature.
Practically in these experiments the gelatin film as if increases the surface tension of poured liquids by an order of magnitude or, in other words, as if decreases the earth gravity for them by an order of magnitude, and their drops turn out to be big because of this fact. And when it was possible to obtain only small lenses (Leeuwenhoek’s lenses were about 1 mm) from the regular solidified drops of liquids, with the film the drops become heavier by an order of magnitude and larger by size. And for them not only bottom but upper plane surface as well, which contacts with air, is smooth, while regular drops did not have this property.
We can judge about the quality of made epoxy lens with the diameter of 16 mm and focal distance of 5 mm according to Fig. 5-7. Undoubtedly, with the technology modernization the properties of such lenses can be improved.
Thermal and electric conductive properties, strength of dried films with possible additions [6] and ability of additionally treated films to have contact and stick to dif-ferent surfaces are of interest for the applications. Also, the capability to obtain long thin threads and waveguides with the web strength from extending hardening soap-gelatin solution is interesting.
Theoreticians predict that the thinnest mono-layer graphene films will have similar elasticity and strength but until graphene films of such dimensions are not available, experimenters can perfect their skills with the samples of soap-gelatin films, which have similar properties.
As it is shown, gelatin films can be used as the simple way of making aspheric lenses which do not have spherical aberration and find many applications [5]. Theoretical study of the form of samples which solidify on the film is still required here but comparison of the published form of typical aspheric lens [5] and photo of solidifying epoxy resin in Fig. 4 shows their good matching (Fig. 8).
An important indirect connection of the properties of soap-gelatin film with laser tracks is discovered in the following manner. It is interesting that expanded in time the process of liquid accumulation in the increasing sagging on the film, in some way rep-resents a visually magnified model of the mechanism of laser tracks formation in thin films. Tracks are also organized in inflection in which liquid from the surrounding ar-eas is accumulated. Therefore, the theoretical consideration of the dynamics of liquid accumulation into stationary form in the center of round horizontal elastic membrane is of interest for the description of the dynamics of laser tracks formation due to the similarity of hydrodynamics of these two processes. While the liquid is accumulated on the membrane in the center of expanding inflection under the action of gravitation and varying in time local pressure of liquid, in the track area the liquid is also accumu-lated in the extruding area of the film [1] but this inflected section is formed at the ex-pense of influence of the pressure of light which is changing in the process of for-mation. Thus, solution of the task in relation to the transformation of flat membrane with the small quantity of liquid on it could be actually used for the description of the process of formation of film thickening in the area of laser track. In such way, gelatin film can assist in the theoretical description of tracks formation.
These unexpected properties of the solution and film were arranged in the form of invention application [7] with the detailed description of the solution composition, with marked applications for the fundamental scientific studies of laser solitons in quantum electronics, with potential applications in optics and mechanics, but as for now it is difficult to evaluate any prospects of their wide implementation or practical application.
Do it has to be repeated, that fundamental science is not aimed at the immediate benefit. It aims in perspective and its necessity will become apparent in future with the growth of society’s needs. And inventors are not guilty that society (more precisely, its leaders) does not realize the need and prospectivity of suggested innovations right away.
For 50 years of work in Lebedev Physical Institute of the Russian Academy of Sciences, many times I patented new inventions which have not found wide applica-tion. I want to emphasize that difficulties in the economic implementation of inven-tions do not indicate their uselessness. Fruits of their applications are usually left for descendants. But inventors refer to the group of people with the special nature and such insignificant things do not stop them. They cannot stop inventing because this is the way they are, such is their psychological type. For details see [2, preprint #12]
I thank my colleagues: A.V. Startsev, V.I. Yalovoy and A.P. Shirokikh for the help in carrying out of the experiments with soap-gelatin film.
Properties of the gelatin films in enclosed volume as well as in air when water evaporates from them turned out to be interesting. Experiments with such films in air not connected with laser tracks directly turned out to be interesting due to some other peculiarities. As it is known, the standard soap bubbles in air usually break, while the transparent rainbow bubbles formed from such gelatin film after drying up do not break but remain in the initial form for weeks (Fig. 1), in other words they become attractive items, decorations and toys for children. As opposed to the known soap polymerized films which set to the solid state in the air and after drying up lose their elasticity, shrink and blow off after 24 hours, gelatin bubbles retain elasticity even without water and after 24 hours can be still noticeably blown and increase in diameter. It shows that thin gelatin film is elastic and poorly permeable for air.
Dried material of films can be dissolved again in small quantity of water and re-used in experiments. The thinness of walls, elasticity and simplicity of obtainment dif-ferentiate the soap-gelatin bubbles from well-known gelatin empty balls with thick walls which are made on the blown rubber balloons using the labor-intensive method of papier-mache.
The distinguished high elasticity, which is not typical for common gelatin- jelly, is caused by the additions of glycerin and soap to it. In such solution a new rubber-like structure with linkage of long molecules of gelatin and glycerin, which was mentioned above, occurs [3]. And addition of a specially selected soap gives opportunity to ob-tain thin films from the solution and strange elasticity (which will be described below in detail) of such films. Observed unusual transformation of jelly-like mass into the "tight and soft" material deserves attention of specialists in this field [4].
Optical properties of the thin gelatin film draw attention as well. Since the initial and dried soap film have smooth surface, even with its partial reflection it can serve as a mirror, radius, focal distance of which can be changed within wide ranges. The examples of such mirror reflections from the film are shown in Fig. 2. But besides the reflectivity, one more wonderful property of gelatin film was discovered.
Judging by the color, film thickness is about 5-10 μm. We can judge on strange and, one can say, even unexpected strength of such a little bit dried film by the load it can bear (Fig. 3, 4). While for regular water soap films the permissible load is deter-mined by its surface tension (of two surfaces) and it is about 0.07 g/cm, here, as we can see, gelatin film without break bears the load of about 1 g/cm which is obviously by an order of magnitude higher and cannot be provided by the simple surface tension. It requires the tension inside of the film, as well.
When the load is removed, the deformed film completely restores its initial form in seconds. In essence, the film turns out to be an example of unusual transparent-specular rubber with attractive capabilities of its use for various optical applications.
For example, load on the film can be in the form of liquid which does not interact with the film and while accumulating in the film center turns into liquid lens with var-iable focal distance (if we change air pressure under the film) Fig. 4. The used poured liquid can be a polymerized one as epoxy resin and after solidification on the film it -l turns into quite good and, which is important to note, aspheric transparent lens with optically smooth surfaces and small focal distance without any additional treatment (Fig. 5-7). Specialists who know the challenges connected with the production of as-pheric optics can duly appreciate such gift of nature.
Practically in these experiments the gelatin film as if increases the surface tension of poured liquids by an order of magnitude or, in other words, as if decreases the earth gravity for them by an order of magnitude, and their drops turn out to be big because of this fact. And when it was possible to obtain only small lenses (Leeuwenhoek’s lenses were about 1 mm) from the regular solidified drops of liquids, with the film the drops become heavier by an order of magnitude and larger by size. And for them not only bottom but upper plane surface as well, which contacts with air, is smooth, while regular drops did not have this property.
We can judge about the quality of made epoxy lens with the diameter of 16 mm and focal distance of 5 mm according to Fig. 5-7. Undoubtedly, with the technology modernization the properties of such lenses can be improved.
Thermal and electric conductive properties, strength of dried films with possible additions [6] and ability of additionally treated films to have contact and stick to dif-ferent surfaces are of interest for the applications. Also, the capability to obtain long thin threads and waveguides with the web strength from extending hardening soap-gelatin solution is interesting.
Theoreticians predict that the thinnest mono-layer graphene films will have similar elasticity and strength but until graphene films of such dimensions are not available, experimenters can perfect their skills with the samples of soap-gelatin films, which have similar properties.
As it is shown, gelatin films can be used as the simple way of making aspheric lenses which do not have spherical aberration and find many applications [5]. Theoretical study of the form of samples which solidify on the film is still required here but comparison of the published form of typical aspheric lens [5] and photo of solidifying epoxy resin in Fig. 4 shows their good matching (Fig. 8).
An important indirect connection of the properties of soap-gelatin film with laser tracks is discovered in the following manner. It is interesting that expanded in time the process of liquid accumulation in the increasing sagging on the film, in some way rep-resents a visually magnified model of the mechanism of laser tracks formation in thin films. Tracks are also organized in inflection in which liquid from the surrounding ar-eas is accumulated. Therefore, the theoretical consideration of the dynamics of liquid accumulation into stationary form in the center of round horizontal elastic membrane is of interest for the description of the dynamics of laser tracks formation due to the similarity of hydrodynamics of these two processes. While the liquid is accumulated on the membrane in the center of expanding inflection under the action of gravitation and varying in time local pressure of liquid, in the track area the liquid is also accumu-lated in the extruding area of the film [1] but this inflected section is formed at the ex-pense of influence of the pressure of light which is changing in the process of for-mation. Thus, solution of the task in relation to the transformation of flat membrane with the small quantity of liquid on it could be actually used for the description of the process of formation of film thickening in the area of laser track. In such way, gelatin film can assist in the theoretical description of tracks formation.
These unexpected properties of the solution and film were arranged in the form of invention application [7] with the detailed description of the solution composition, with marked applications for the fundamental scientific studies of laser solitons in quantum electronics, with potential applications in optics and mechanics, but as for now it is difficult to evaluate any prospects of their wide implementation or practical application.
Do it has to be repeated, that fundamental science is not aimed at the immediate benefit. It aims in perspective and its necessity will become apparent in future with the growth of society’s needs. And inventors are not guilty that society (more precisely, its leaders) does not realize the need and prospectivity of suggested innovations right away.
For 50 years of work in Lebedev Physical Institute of the Russian Academy of Sciences, many times I patented new inventions which have not found wide applica-tion. I want to emphasize that difficulties in the economic implementation of inven-tions do not indicate their uselessness. Fruits of their applications are usually left for descendants. But inventors refer to the group of people with the special nature and such insignificant things do not stop them. They cannot stop inventing because this is the way they are, such is their psychological type. For details see [2, preprint #12]
I thank my colleagues: A.V. Startsev, V.I. Yalovoy and A.P. Shirokikh for the help in carrying out of the experiments with soap-gelatin film.
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