 Anywhere you go these days, if you touch a piece of electronics, you'll notice that it gives off a lot of heat. Military systems are growing in complexity and include more and more electronic components. Army researchers are on the hunt to mitigate the effects of that heat. Discovering thermal management solutions will help deliver efficient and effective tools for the soldier of tomorrow. Hi, I'm Dr. Phil Percanti, the Director of the U.S. Army Combat Capabilities Development Commands, Army Research Laboratory. Welcome to ARL, What We Learned Today. In this podcast, we have a conversation with Army scientists and engineers who are intimately involved in the discovery, innovation, and transition of science and technology that will modernize the United States Army. Today, we are going to talk with Dr. Lauren Bowler. Lauren leads the thermal and packaging research programs as part of the Advanced Power Electronics Group at our Adelphi Laboratory Center in Maryland. Lauren, welcome to the podcast. Thanks for having me. It's really nice that you're here. I understand that you're working in thermal and packaging research. Can you tell me a little bit about that? Sure. So Army is moving into more electrified forces. In general, all of our systems are becoming more electrified. Our vehicles are becoming more electrified. Our weapons are becoming more electrified. And as part of that, you have to build the thermal and packaging solutions to be able to leverage these new technologies. So what does it mean to be electrified? Is that like going from an acoustic guitar to an electric guitar? It kind of is. But in weapons, for instance, we used to have weapons that were based on mechanical systems. And now we're moving into electric weapons, for instance, with directed energy weapons, as well as our vehicles. We're moving away from motors and into electric drivetrains. So what's happening in the commercial world is also happening in the military. We're moving into more electrified systems. So that means a lot of batteries on platforms, right? It does mean a lot of batteries on platforms. Does it mean a lot of heat, too? It does mean a lot of heat. So how do you get the heat out? So there's a number of ways to get the heat out. There's ways heat sinking. It's primarily, if it's a high power electronic system, you put a liquid cooled flow loop. So on vehicles, for instance, we have a water ethylene glycol, a 50-50 WAG loop, that cools most of our electronics that goes through the vehicle. So that's like antifreeze. And so we use that to cool most of our electronics in the high power range. You can also air cool, but at certain power densities, air cooling becomes unrealistic to think that you can cool it using air. But in general, every electronics are actually air cooled. At some point, that WAG loop does need to reject to the air cooled environment. So the way I think about it is you have to cool because you're generating heat. The heat is being generated by inefficiencies in something, either the electronics or some other part of the system, right? Yes. So do you think about this from a system perspective? So you have to, when you think about getting heat out, could you trade off, say, more efficient electronics? Yes. I think it has to be a combination. I think it has to be a systems of systems approach. When it comes down to it, the devices are the only actual functioning component. You have the devices and then after that you have your packaging and then your heat sink and then that when you have your entire flow loop and your radiator, and all of that is supporting technology to the devices. So more efficient devices can alleviate the amount of heat and the amount of system that you need designing for application, reducing overt design and designing for the application. It has to be a systems of systems approach. Whereas if you do something here to make your packaging more efficient or your thermal management more efficient, it can change the entire system. So, Lauren, how long have you been at ARL? I started at ARL in 2005. 2005 as a PhD? I was an undergrad and then I worked here during my master's and my PhD. So the Army paid you to go to school? Yes. So that is one of the really cool things about coming to work for the United States government and particularly the United States Army because we will pay for our staff not necessarily to get degrees but to improve their ability to do work through formal education. So the more educated you are, the more knowledge you have with regard to your discipline, the better off the Army is. So we think that's a great investment in people. Yeah, and it's great to have when I'm working on my PhD project, to have a nice application with the soldier and the military be able to work towards benefiting the soldier in my technology that I'm working on as a PhD student. So where did you go to school? I went to University of Maryland. Oh, right next door. Yes, it was convenient. Yes, how nice. Yes. And what did you study there? Mechanical engineering. Okay, so now I get it. So your degrees in thermodynamics or something else? I actually started more as a packaging engineer building electronics and I started one of my PhD advisor had a program through the Army Research Laboratory and I was doing package reliability as part of that research and I realized that I never actually built electronics. So I started here as an intern over the summer to be able to get a hands-on. We have an electronics packaging laboratory here and so I started working there to be able to actually physically build the electronics packaging. And then from that you quickly realized that it's the thermal management that what's limiting most of the technologies and so then I transitioned and became part of the thermal sciences and engineering team here. So is there a particular curriculum in Maryland for thermal sciences? You can do, not necessarily, you can do a thermal track in a master's degree. Certainly take classes related to thermal and packaging as well. They have a very strong packaging group as well, especially in the master's degrees and PhD, but not necessarily. So of all the things you could have studied, why this? Why packaging? In some ways I fell into it, in some ways you start to realize, for me it's most interesting because it's multidisciplinary. It brings all the disciplines together. To build an electronics module you need electrical engineers and thermal engineers and mechanical engineers and reliability engineers and materials engineers and everybody needs to come together to be able to, physicists. It's really one of those truly multidisciplinary areas of research. You have to understand them. If you want to really make an impact you need to understand these other domains and how they start to play a role with each other because a better thermal management solution is only going to get you so far. You need a better package. You need a better thermal management solution. You need a better device. You need a better control circuitry. All of this needs to come together to really make an impact on the electronics. So you really get a piece of understanding of the entire system, as you said. Yes. It's kind of a systems-to-systems thing. It is, and it's multidisciplinary. And I think that if you want to make real impact, for example, you can make a better heat sink, but you can make a better package. You can make a better circuit. But it's really about tying all those better circuits, better packaging, better heat sinks together to really create true impact and really revolutionary design. That's really insightful. And we talk about multidisciplinary research all the time. It really is the norm rather than the exception for the future, I think. I agree. You're out in front. Yes. And I sort of fell into an electrical group here. I primarily work with a lot of electrical engineers. And so that's helped me see this bigger picture perspective by working here in that multidisciplinary group. I don't think necessarily when you think about packaging and thermal management, I mean, this is a problem that's pervasive in all electronics. You think about servers and cloud computing. I mean, there's an enormous heat problem there. So I would imagine that many of the major companies, particularly the large electronics firms, all have a group who are focused on thermal management to some degree or another. What do you think is unique about what you do for the Army? Like, why couldn't we go somewhere else to get what you do? So what we do that's unique is we have a program focused on co-engineering co-design, which is putting these electrical, thermal, mechanical systems together. And a lot of bigger companies, it's very a siloed approach to design where you can create a better, I guess I said this earlier, but you can create a better heat sink. You can create a better circuit. But really what we're doing that's different is pulling these different technologies together. And we're developing another area that we're really big on is developing the design tools that can then tell you where the most appropriate ways are to improve the design. So if you're understanding huge design spaces, you want to be able to say, this will lower my inductance. It'll improve my performance. It'll reduce my temperature. It'll create X percentage reduction in size and weight. You need design tools to be able to do that. And so that's an area that we're making a lot of progress in here is developing tools to be able to do quick parametric studies that can handle tens of millions of simulations very, very quickly. We like to think that we are speaking a language that everybody understands. But when you use the words parametric studies, I'm not so sure everybody knows what that means. Okay. So why don't you tell us a little bit about what a parametric study is and how you do your modeling and simulation? Sure. So if you have, I guess this initial program started seven or eight years ago and somebody came to me and they said, I wanted you to do some thermal design. And I said, okay, what's your devices? And they said, we don't know yet. And I said, what are your materials? And they said, we don't know yet. And I said, what are your dimensions? And they said, we don't know yet. And so when you're starting very early in the design process and you want to understand the entire design space, but you don't have any constraints, that's your parametric space. It's all of these design constraints coming together. All the materials you're considering, all the geometries you're considering. And if you want to look into across a parametric space where you're not just looking into thermal, but then you're also looking into the materials and the inductance of different loops can create different higher inductances can lead to lower switching frequencies. And so you have issues across these multiple domains. And so we want to look at this entire parametric space and understand how every design decision that we make and then ideally the idea would be to optimize, figure out what our sensitive parameters are, the ones that'll make the biggest influence on the design and then also the insensitive parameters. Moving into this technology isn't really going to buy us anything because at that point you've sort of saturated your performance benefits. And so we don't want to look into those technologies. And so we want to understand this entire design and parametric space. Gotcha. So I think you mentioned it earlier, the need to do thermal management for high-energy laser systems. So the Army is looking very hard at whether or not high-energy lasers should be on the battlefield and what capabilities the Army might bring to the future. I think the high-energy laser may show up on the battlefield at some point. The question is how much power is going to be in a laser? How large the platform will be and whether or not the Army can take full advantage of the capabilities that a weapon like a high-energy laser may have should the United States ever get into a long protracted war? As we know here, lasers are particularly inefficient. The more you try to get out of them from an optical power perspective, the more electrical power you have to put in. And I think it's that inefficiency that creates this enormous heat control that you have to contend with. So my question for you is, given everything you've learned today, what do you think we can say about thermal management for high-energy lasers? So directed energy weapons are interesting because they have a thermal magazine. What is a thermal magazine? A thermal magazine is how long you can shoot and the amount of energy that you can shoot. The time on target is strictly dependent on your ability to remove the heat from the system. It's not based on the number of bullets you can put into a gun or it's strictly a thermal limit. And a lot of times your ability, the length that you can shoot and the amount of energy that you can shoot is strictly dependent on how much heat you can get out of the system. Because things will melt or because the beam will lose its optical quality and won't be able to focus or all the above? So the laser diodes are extremely temperature dependent, which means at this point there are programs looking into temperature-stabilized, higher-temperature diodes. Right now the diodes operate at very low temperatures and any deviation from that temperature causes inefficiency in the output wavelength. And so when you deviate outside of that designed wavelength, you lose system inefficiencies. Wavelength is the color of the light, so to speak. And so the entire system is usually designed on these laser diodes outputting a given wavelength. And so when you deviate from that given wavelength, your entire system, because at that point now you have your optics where you have an array of a lot of these laser diodes that are assembled together, each one of them outputting a certain amount of energy and then you coalesce all of these individual wavelengths together to create beams. And at that point if you deviate and any one of them isn't outputting it because it's not operating at the temperature you've designed for, you can start getting system inefficiencies. And they are at this point still very inefficient. You're talking 100 kilowatt system that's only 30% efficient. There's a lot of heat that's being generated. There's a lot of heat that's being generated and there's a lot of electrical power that needs to go in. Exactly. So there's power electronics and thermal management and it's a very unique challenge because it is a very transient problem. You think of a lot of vehicles for instance and even a lot of directed energy weapons. These days are designed with a constant flow rate going through the system. A constant flow rate of cooling? Exactly. If you're looking into a directed energy weapon it's not shooting 100% of the time. It has a certain upper limit of which you can design for and at that point there's a reload or a reset that can happen and designing thermal and packaging and electronics related to this very transient nature of the directed energy weapons is where real system improvements can be made. So what do you think? The research you're doing, what have we learned? Let's say lasers stay as efficient as they are. We don't make any improvements. What can we do from a packaging and cooling point of view? So one of our programs is looking into putting metallic phase change materials directly in contact with the laser diode. So what's a phase change material? A phase change material is a material that changes phase. We're focused on solid to liquid phase change. Now we're looking at metallics and so if you think about it when you change state you can absorb a huge amount of energy and a glass of ice water for instance as that ice melts in that glass that glass of ice water is always at zero degrees until that ice fully melts at which point then it'll start to rise in temperature again. And so we're doing the same thing in our electronics. We're putting a metallic phase change material that has a given melt temperature based on our application and as you heat it up that can absorb a huge amount of energy and stabilize the temperature through the entire pulse and then at which point at the end of the pulse you can resolidify the material. So it's a real disruption because it will increase the thermal magazine? So it can do a number of things. You can either have less number of diodes in the system. You can reduce the amount of cooling you have. You can put more power into each diode. There's a number of ways that once you start saving energy you can make a smaller system or you can make a same size system with more power or you can reduce the cooling on the electronics. There's a number of different ways and once you start to improve this you can start doing swap analysis or system size, weight and performance analysis to figure out where you want the benefit to be. And how far away do you think we are before we see metallic phase change thermal management system in the field? I think with the right interest it could be seen within five years. There's a lot of technical complexities at this point. Material compatibility is a challenge. Long-term reliability is a challenge. Material selection is a challenge. Even in terms of how to properly design these because they are very system dependent application dependent you have to make sure that you properly design them based on the system. So one size fits all solution isn't going to work. So the proper design tools associated with understanding how these affect the system is very important. You're in an area of science that fundamentally if you don't make improvements in I don't believe you'll see the real disruption in high energy or directed energy weapons nor actually do I think you'll see improvements in quantum information science at least quantum computing at a very small scale or artificial intelligence at the cloud based or server level where all three of those technologies can generate quite a bit of heat and if it's not managed properly we'll never get into the form factor that the army is looking for for the future. So while in description it might sound a little mundane to talk about thermal packaging it's really very exciting and totally useful for an army to think about these things. I agree it's a really cross cutting technology it's not necessarily tied to any one application what we're developing for directed energy weapons we have similar programs for power electronics as we move to more electrified vehicles. Not to mention the electrified vehicles. And so as you move into these more electrified systems thermal and packaging is a very crucial portion of every one of these technologies and so being able to leverage advanced technologies and there's a lot of system benefits and we've showed some of our programs have looked into replacing standard electronics modules with these really high performing packages to get 40 times higher power density. So that's a way to but you know individual technology by itself is when you start integrating these multiple technologies is when you can start seeing system improvements. Well thanks it's really interesting and I really appreciate your passion for this area because it's very very important for the future. Well thanks for joining us for ARL what we learned today in upcoming episodes we'll continue the discussion about the disruptive research that will fundamentally change the army of the future and make American soldiers stronger and safer. Please consider liking and subscribing. As always science is a journey of discovery and we're glad you're along for the ride. For the Army Research Lab I'm Dr. Phil Percontin.