WEBVTT 1 00:00:00.100 --> 00:00:05.100 (chalkboard pops) (ethereal music) 2 00:00:05.368 --> 00:00:06.900 - I'm Xiulin Ruan, I'm a professor 3 00:00:06.900 --> 00:00:08.760 in the school of mechanical engineering 4 00:00:08.760 --> 00:00:11.520 and the Birck Nanotechno Center at Purdue University. 5 00:00:11.520 --> 00:00:13.170 We're trying to find ways, you know, 6 00:00:13.170 --> 00:00:16.023 can we come up with materials that can help, 7 00:00:17.010 --> 00:00:18.720 you know, the energy sector. 8 00:00:18.720 --> 00:00:21.090 - Obviously people have known 9 00:00:21.090 --> 00:00:24.120 for a while that white paint reflects sunlight 10 00:00:24.120 --> 00:00:25.590 and can help keep buildings cool. 11 00:00:25.590 --> 00:00:28.020 Like what's kind of the difference between 12 00:00:28.020 --> 00:00:30.630 what you set out to address and the difference between 13 00:00:30.630 --> 00:00:33.060 like, what you can buy in, you know, Home Depot 14 00:00:33.060 --> 00:00:35.160 or sort of the whitest paint that was available? 15 00:00:35.160 --> 00:00:36.510 - That's a great question actually. 16 00:00:36.510 --> 00:00:39.870 Indeed, commercially available white paints, 17 00:00:39.870 --> 00:00:41.610 they can cool surfaces better 18 00:00:41.610 --> 00:00:43.380 than the darker color surfaces. 19 00:00:43.380 --> 00:00:46.140 However, you know, the paints available, 20 00:00:46.140 --> 00:00:50.730 they reflect sunlight to the level of 80-90%, which means 21 00:00:50.730 --> 00:00:54.390 that these paints still absorb 10-20% of sunlight. 22 00:00:54.390 --> 00:00:58.680 Although they emit infrared heat to the deep space, 23 00:00:58.680 --> 00:01:00.540 but the absorbed sunlight is too much. 24 00:01:00.540 --> 00:01:02.970 So what we really pushed about our paints 25 00:01:02.970 --> 00:01:07.320 is to minimize the absorption to the sunlight. 26 00:01:07.320 --> 00:01:11.100 So, that's why the whitest comes to the picture. 27 00:01:11.100 --> 00:01:15.300 We were able to reduce the absorption 28 00:01:15.300 --> 00:01:20.210 to less than 2% because our reflectance is a 98.1%. 29 00:01:21.510 --> 00:01:22.620 Okay, that's a big deal. 30 00:01:22.620 --> 00:01:24.510 That cut down the absorption 31 00:01:24.510 --> 00:01:26.580 to the sunlight by a factor of 5 to 10. 32 00:01:26.580 --> 00:01:27.990 That's why it took so many years, 33 00:01:27.990 --> 00:01:32.040 'cause we really had to combine all these factors 34 00:01:32.040 --> 00:01:33.870 and push them into extremes 35 00:01:33.870 --> 00:01:35.700 to achieve this extreme performance. 36 00:01:35.700 --> 00:01:37.620 If we miss one of them, 37 00:01:37.620 --> 00:01:40.350 performance definitely would not be there. 38 00:01:40.350 --> 00:01:44.280 After we kind of published our cal site 39 00:01:44.280 --> 00:01:45.900 and the barium sulfate formulations 40 00:01:45.900 --> 00:01:50.190 we got a all of inquiries, especially people from 41 00:01:50.190 --> 00:01:54.360 for example, aerospace industry, space industry, 42 00:01:54.360 --> 00:01:58.080 and even wearables or clothing companies. 43 00:01:58.080 --> 00:02:00.360 They ask us two questions, you know 44 00:02:00.360 --> 00:02:01.590 can you make it distincter? 45 00:02:01.590 --> 00:02:02.610 Can you make it lighter? 46 00:02:02.610 --> 00:02:05.100 They had to look for the solutions. 47 00:02:05.100 --> 00:02:08.010 I mean, we got inspired actually 48 00:02:08.010 --> 00:02:09.240 by the different morphology. 49 00:02:09.240 --> 00:02:12.330 I mean the hexagonal boron nitride, 50 00:02:12.330 --> 00:02:15.360 it has a platelet geometry. 51 00:02:15.360 --> 00:02:18.900 So intuitively these platelets can, you know 52 00:02:18.900 --> 00:02:20.520 block the light more effectively 53 00:02:20.520 --> 00:02:24.330 because they have a larger cross-sectional area. 54 00:02:24.330 --> 00:02:28.350 So yeah, we experimented this material and again 55 00:02:28.350 --> 00:02:31.920 there are some challenges because it bounce back better. 56 00:02:31.920 --> 00:02:34.200 Also make the paints much more viscous. 57 00:02:34.200 --> 00:02:37.200 So initially we're not able to really brush or spray 58 00:02:37.200 --> 00:02:38.820 it's just like a gel. 59 00:02:38.820 --> 00:02:42.750 So it, again, it took us some journey to figure out 60 00:02:42.750 --> 00:02:45.600 how to use the right solvent, right binder, 61 00:02:45.600 --> 00:02:48.747 and make it paintable, sprayable and brushable. 62 00:02:48.747 --> 00:02:51.930 And so it turns out that now with this new formulation 63 00:02:51.930 --> 00:02:55.260 we're able to achieve nearly the same reflectance 64 00:02:55.260 --> 00:02:58.110 at only 150 micron thickness. 65 00:02:58.110 --> 00:02:59.850 That's a kind of a significant reduction. 66 00:02:59.850 --> 00:03:02.040 The weight reduction is even more, 67 00:03:02.040 --> 00:03:06.180 because density is much less than the barium sulfate. 68 00:03:06.180 --> 00:03:08.070 - Can we buy these paints in stores? 69 00:03:08.070 --> 00:03:10.230 Like what other kinds of paints are you guys gonna like 70 00:03:10.230 --> 00:03:12.060 look at, like, going into? 71 00:03:12.060 --> 00:03:13.950 Like what's on the horizon for you all? 72 00:03:13.950 --> 00:03:14.783 - Sure. Yeah. 73 00:03:14.783 --> 00:03:19.320 Currently we are partnering with industry collaborators 74 00:03:19.320 --> 00:03:21.090 in the process of commercialization. 75 00:03:21.090 --> 00:03:23.970 There are a few issues we are working on. 76 00:03:23.970 --> 00:03:27.150 We need to have a test on the durability 77 00:03:27.150 --> 00:03:29.820 and make sure it can last as long 78 00:03:29.820 --> 00:03:32.850 as the commercially available paints. 79 00:03:32.850 --> 00:03:35.640 The second of many applications, we would like to 80 00:03:35.640 --> 00:03:38.550 minimize the use of solvents. 81 00:03:38.550 --> 00:03:41.610 So that it is environmentally friendly. 82 00:03:41.610 --> 00:03:43.680 Okay, so this is ongoing right now 83 00:03:43.680 --> 00:03:46.680 and hopefully we can push the white paints, you know 84 00:03:46.680 --> 00:03:48.540 in a reasonable amount of time. 85 00:03:48.540 --> 00:03:53.160 And going next we try to develop color paints 86 00:03:53.160 --> 00:03:56.010 based on our white paint formulation because, 87 00:03:56.010 --> 00:03:59.400 you know, color paint is developed by 88 00:03:59.400 --> 00:04:01.740 mixing the colorants to the white paints. 89 00:04:01.740 --> 00:04:06.510 So, our white paint does provide a good platform 90 00:04:06.510 --> 00:04:09.270 for that new development. 91 00:04:09.270 --> 00:04:11.400 The other development we're thinking is, you know 92 00:04:11.400 --> 00:04:12.990 can we switch 93 00:04:12.990 --> 00:04:15.960 between cooling in the summer and heating in the winter? 94 00:04:15.960 --> 00:04:19.710 So this will make the paints not only be very attractive 95 00:04:19.710 --> 00:04:23.940 to the hottest climates, but for, you know 96 00:04:23.940 --> 00:04:26.670 the climate zones with seasons. 97 00:04:26.670 --> 00:04:29.280 it will be able to save the energy better, 98 00:04:29.280 --> 00:04:31.323 and help out with our climate better.