WEBVTT 00:00.000 --> 00:03.020 Bionics describes technology that imitates mother nature. 00:04.100 --> 00:07.720 Evolution performs true miracles when it comes to the adaptation of 00:07.720 --> 00:12.760 innumerable generations in a way to certain living conditions and 00:12.760 --> 00:18.080 shows science abbreviations for certain problems that it probably 00:18.080 --> 00:19.200 would not have come to. 00:19.700 --> 00:23.420 So the researchers of the Carso Institute for Technology have 00:23.420 --> 00:27.840 succeeded in developing a material, for example, for solar cells, that 00:27.840 --> 00:33.660 the sunlight could absorb up to 200% better than conventional solar 00:33.660 --> 00:34.260 cells. 00:34.600 --> 00:38.840 This was made possible by the example of a butterfly whose wings are 00:38.840 --> 00:43.220 completely transparent, a kind of camouflage cap with which the glass 00:43.220 --> 00:46.340 -winged man with the Latin name Greta Oto makes himself invisible to 00:46.340 --> 00:47.360 his predators. 00:49.120 --> 00:52.960 The special thing about the butterfly is that it has wings that are 00:52.960 --> 00:54.740 largely transparent. 00:54.740 --> 00:59.040 This means that if you now put the butterfly, one that no longer 00:59.040 --> 01:03.240 lives, on a magazine, you can look through the wings wonderfully. 01:04.240 --> 01:07.460 But there are also wonderful photos of how such glass-winged 01:07.460 --> 01:11.460 butterflies sit on plants and you can also look through the wings. 01:12.840 --> 01:16.360 The wings are not completely transparent now, but very, very large 01:16.360 --> 01:17.460 parts of them. 01:18.020 --> 01:23.040 The assumption is that the wings are so transparent that when the 01:23.040 --> 01:26.460 butterfly flies, it is difficult for predators, i.e. 01:26.500 --> 01:33.540 for birds, to focus on the flying butterfly and then to prey on it and 01:33.540 --> 01:34.580 to devour it. 01:34.640 --> 01:38.300 Professor Hendrik Hölscher works at the Institute for Microstructure 01:38.300 --> 01:41.280 Technology of the Carso Institute for Technology. 01:41.960 --> 01:46.100 Many colourful folds and butterflies in showcases on the walls of his 01:46.100 --> 01:50.980 study room show how much his research group is based on the example of 01:50.980 --> 01:56.080 nature to develop materials with extraordinary properties. 01:57.220 --> 02:00.880 With this particular butterfly, we found it by chance. 02:01.380 --> 02:06.280 A PhD student of mine saw it in the Louisen Park and was very 02:06.280 --> 02:11.000 fascinated that you could hardly see it while it was flying and then 02:11.000 --> 02:12.800 took a closer look at it. 02:13.200 --> 02:15.680 But we also screen quite systematically, i.e. 02:15.720 --> 02:20.260 we regularly look through corresponding magazines to see what rare 02:20.260 --> 02:24.500 plants and animals there are that we suspect could have special 02:24.500 --> 02:28.940 properties that are interesting to us, that can be technically 02:28.940 --> 02:31.060 imitated and implemented into products. 02:32.140 --> 02:37.080 Irregular columns in the nano area provide for the special optical 02:37.080 --> 02:41.960 properties of the transparent wings of the Cretaceous autofold. 02:42.360 --> 02:45.960 Extreme light absorption and no reflection even in low light. 02:48.300 --> 02:52.880 They resemble the so-called moth's eye with which a whole series of 02:52.880 --> 02:54.260 insects are equipped. 02:54.960 --> 02:59.200 The principle used by the butterfly and, as we now know, by some other 02:59.200 --> 03:04.440 butterflies, has to do with the moth's eye effect in the broadest 03:04.440 --> 03:04.440 sense. 03:04.940 --> 03:07.140 It was studied more precisely in the 1960s and 1970s. 03:08.140 --> 03:12.700 Small nanostructures have been found on the facet eyes of many 03:12.700 --> 03:13.180 insects. 03:14.300 --> 03:20.080 They use these column structures so that they can absorb light very 03:20.080 --> 03:25.020 well in the dark and, on the other hand, very little light is 03:25.020 --> 03:29.340 reflected from the facet eyes, so that they are not easily 03:29.340 --> 03:29.840 recognizable for predators. 03:30.520 --> 03:33.780 With the facet eyes, the structures are extremely regular. 03:34.420 --> 03:36.400 It looks very interesting. 03:37.040 --> 03:41.320 You can imagine them like little nipples that are very close together. 03:41.700 --> 03:46.960 They are so small that they are perceived as a continuum for the 03:46.960 --> 03:46.960 visible light. 03:47.840 --> 03:51.020 As a result, the light is transferred very well into the facet eyes. 03:52.340 --> 03:57.700 The butterfly uses the principle in a similar way. 03:57.920 --> 03:59.920 However, the structures are very irregular. 03:59.920 --> 04:05.760 You can see that they seem to be similar columns that are the same 04:05.760 --> 04:08.880 size as found in the eyes of moths. 04:09.000 --> 04:13.580 On the other hand, they are very different both in position and 04:13.580 --> 04:14.200 height. 04:14.820 --> 04:16.620 They also vary a bit in diameter. 04:17.580 --> 04:21.840 They move in a diameter of about 100 nanometers, so they are very, 04:21.880 --> 04:22.480 very small. 04:22.580 --> 04:26.920 The distance is in the order of maybe 200 nanometers. 04:26.920 --> 04:31.100 200 nanometers is also the order of size that can be found in the eyes 04:31.100 --> 04:31.240 of moths. 04:31.980 --> 04:37.880 The butterfly makes the structures even smaller and arranges them a 04:37.880 --> 04:39.160 bit more randomly. 04:39.580 --> 04:43.900 We were interested in the advantage of arranging them so randomly. 04:45.240 --> 04:49.040 We analyzed these small nano columns in more detail. 04:49.240 --> 04:54.180 We found that they are arranged in such a way that they are more or 04:54.180 --> 04:58.260 less a perfect transition for an anti-reflection layer. 04:59.160 --> 05:02.800 This is of course important for the butterfly because, unlike the eyes 05:02.800 --> 05:04.340 of moths, you don't just look at it vertically. 05:05.100 --> 05:10.500 It also has to be transparent for high angles and the reflection has 05:10.500 --> 05:11.320 to be prevented. 05:12.060 --> 05:16.060 For a more detailed analysis, the Karlsruher research team simulated 05:16.060 --> 05:19.960 the surface structure of the glass wings in the computer model. 05:19.960 --> 05:23.540 If you have such irregular structures, you can usually only simulate 05:23.540 --> 05:27.640 them in the computer because the calculations are a bit more complex. 05:28.160 --> 05:29.500 We simplified it a bit. 05:30.160 --> 05:34.260 We made a model and first of all thought analytically if we have a 05:34.260 --> 05:37.820 random arrangement of nanostructures as we find them on the butterfly. 05:38.380 --> 05:41.600 How can we describe this analytically through a function? 05:42.560 --> 05:45.040 We can find an analytical function for this. 05:45.440 --> 05:48.780 This is called a transmission matrix, which is calculated in the end. 05:50.140 --> 05:53.920 We put it in the computer and calculate it for different angles, 05:54.200 --> 05:55.040 different wavelengths. 05:55.620 --> 05:59.900 How is the transmission and the reflection on these butterfly wings? 06:00.400 --> 06:03.800 Then you can show that this is very, very well consistent with the 06:03.800 --> 06:05.540 experiments that we have done. 06:06.520 --> 06:09.920 In other words, theory and experiment are well consistent. 06:10.020 --> 06:13.960 On the transparent wings of the butterfly, the researchers discovered 06:13.960 --> 06:18.460 additional small hairs, whose function was initially puzzling. 06:19.120 --> 06:22.400 The special thing about butterflies is that they have quite a 06:22.400 --> 06:25.760 complicated structure on the one hand of scales and on the other hand 06:25.760 --> 06:27.260 they have a wing membrane. 06:27.540 --> 06:29.960 These scales are attached to the wing membrane. 06:31.320 --> 06:34.540 These scales are usually responsible for the special colors of 06:34.540 --> 06:35.100 butterflies. 06:36.540 --> 06:38.420 Here the butterfly is now transparent. 06:38.420 --> 06:41.480 But it's not like he doesn't have the scales anymore. 06:43.160 --> 06:45.680 Instead, they have degenerated scales. 06:45.740 --> 06:47.140 They look like little hairs. 06:47.880 --> 06:50.980 We first asked what these little hairs are for. 06:51.420 --> 06:53.100 They are relatively large. 06:53.220 --> 06:56.180 That means the distances between the individual hairs are large. 06:56.660 --> 06:59.980 The diameters are also a few tens of micrometers and they are a few 06:59.980 --> 07:01.160 hundred micrometers long. 07:01.900 --> 07:08.840 We could then simply pull these individual hairs out of the membrane. 07:09.340 --> 07:11.440 Then you only have the membrane without the little hairs. 07:11.720 --> 07:15.200 We found that this practically does nothing for the optical behavior. 07:16.700 --> 07:22.080 That means the transparency or non-reflection with and without these 07:22.080 --> 07:25.900 hair -like structures, without the scales, is more or less the same. 07:26.480 --> 07:29.040 But it is also an interesting example that it is usually the case in 07:29.040 --> 07:33.300 nature that surfaces are multifunctional. 07:33.300 --> 07:36.300 That means the butterfly does not only want to achieve that it is 07:36.300 --> 07:40.560 particularly transparent, but he also wants to achieve that, for 07:40.560 --> 07:44.280 example, if there are fog, rain or water drops, they should fall off 07:44.280 --> 07:45.300 his wings. 07:46.320 --> 07:48.900 For this he still needs these scales. 07:49.780 --> 07:53.600 They are also arranged in such a way that the whole thing is still 07:53.600 --> 07:54.620 super hydrophobic. 07:54.900 --> 08:00.840 That means this surface contains the nanostructures that cause the 08:00.840 --> 08:06.680 anti -reflection effect and on the other hand these degenerated scales 08:06.680 --> 08:11.260 that cause the super hydrophobicity so that the butterfly rejects 08:11.260 --> 08:12.420 water very, very well. 08:12.860 --> 08:16.580 For one, the structure of the butterfly wing imitates the material, 08:16.880 --> 08:20.940 there is a large range of possible applications, especially since it 08:20.940 --> 08:25.960 can be laid out much thinner than the well-known mirrored surfaces 08:25.960 --> 08:27.900 that consist of several layers. 08:29.460 --> 08:31.320 Recycling would also be easier. 08:31.680 --> 08:35.440 The idea is that there are numerous surfaces where it is an advantage 08:35.440 --> 08:37.360 if they do not have high reflections. 08:37.900 --> 08:41.300 This could be, for example, with solar cells where you want as much 08:41.300 --> 08:42.660 light as possible to be absorbed by the solar cell. 08:44.120 --> 08:47.240 But there can also be other optical components. 08:48.400 --> 08:52.580 A simple pair of glasses or optics where you would like them to stay 08:52.580 --> 08:56.240 particularly clean and at the same time have an anti-reflection 08:56.240 --> 08:56.800 effect. 08:57.180 --> 08:58.580 Here is the problem. 08:58.840 --> 09:03.380 You can already apply these nanostructures to different surfaces, but 09:03.380 --> 09:06.400 then you have to make sure that the surface is not destroyed. 09:06.920 --> 09:11.480 Such nanosurfaces also have the property that they reject water very, 09:11.480 --> 09:13.680 very well, but also absorb fat very, very well. 09:13.680 --> 09:16.840 This means that you cannot directly put the structure of the butterfly 09:16.840 --> 09:18.340 on a pair of glasses. 09:19.420 --> 09:23.580 If I then touch my glasses, the fat would penetrate these 09:23.580 --> 09:26.940 nanostructures very well and it is then relatively difficult to clean 09:26.940 --> 09:27.140 it. 09:27.600 --> 09:32.320 If you want to implement this technically, you will probably have to 09:32.320 --> 09:36.220 combine the whole thing with other structures, other properties, other 09:36.220 --> 09:40.320 materials in order to ensure that the surface does not get dirty. 09:40.940 --> 09:43.300 We have already tried some technical implementations. 09:44.060 --> 09:48.340 It works in principle, but if you want to apply it to real products, 09:49.420 --> 09:52.180 you still have to take into account that they have to be scratch 09:52.180 --> 09:56.260 -resistant, they usually have to have a self-cleaning effect and 09:56.260 --> 09:57.740 should not absorb any fat if possible. 09:58.300 --> 10:00.200 And that just makes it difficult and complicated. 10:00.560 --> 10:03.880 Because sometimes going a long way from the role model of nature to 10:03.880 --> 10:08.120 the finished products together with an interested industrial partner 10:08.120 --> 10:13.280 is one of the tasks of the Institute for Microstructure Technology. 10:13.300 --> 10:18.520 We always try to bring things that we have found in nature to the 10:18.520 --> 10:18.780 market. 10:19.140 --> 10:21.620 That means we look around for companies that might be interested. 10:22.520 --> 10:26.600 They always get in touch and compare it with the solutions that are 10:26.600 --> 10:29.920 already on the market or solutions that they have already found. 10:30.440 --> 10:34.120 And then our solution has to be significantly better or the legal 10:34.120 --> 10:37.420 regulations have to be in such a way that our solution meets them. 10:37.660 --> 10:41.820 That's the problem with the disposal or recycling of materials. 10:42.280 --> 10:44.000 But it's usually a long process. 10:44.100 --> 10:48.320 You have to have a certain lever somewhere that I have a product where 10:48.320 --> 10:52.760 our solution is so good that you can even use it to develop it 10:52.760 --> 10:53.520 further. 10:54.200 --> 10:58.360 Because it's not like we can make it on the square meter scale right 10:58.360 --> 10:59.040 away. 10:59.040 --> 11:02.800 Instead, we start with the laboratory scale and think about how we 11:02.800 --> 11:03.980 could make it on a larger scale. 11:04.880 --> 11:07.700 But to scale it up costs a lot. 11:07.820 --> 11:12.820 And you can only do that if you already have a product where you can 11:12.820 --> 11:13.460 use the whole thing. 11:13.880 --> 11:18.240 And then the whole thing can maybe also spread on the market and be 11:18.240 --> 11:19.240 used for other products. 11:20.260 --> 11:22.600 We are constantly looking for new bionic solutions. 11:22.880 --> 11:26.120 We always have solutions that are interesting. 11:26.120 --> 11:31.260 For example, we have surfaces that are white through a nanostructure. 11:31.460 --> 11:34.000 We have surfaces that can separate water and oil. 11:35.260 --> 11:38.040 And for this and other solutions we always look for partners to bring 11:38.040 --> 11:39.020 the whole thing to the market.