the innate immune system. It modulates something in your body. But the fascinating realization was how natural nature is, in that we always have thought of receptor-ligand interactions as: There’s something on the surface of the cell. It rings a doorbell. Something happens. Very binary. What we’ve realized now is that none of this is binary. It’s all integrated and it all flows together.
The receptor seems to be feeling the ligand rather than just binding it. It’s not a one-to-one trigger. And the surface area of the receptor is large enough to kind of envelop the ligand, and it changes its shape in a very subtle manner, and that causes a very subtle change inside the cell. So when we make tiny alterations to the molecule that binds, we get a big alteration in how the cells respond. It bothered me in some senses, for the longest time, because as a biophysicist, you’re taught this binds, this brings, this happens. I think what we’ve been doing is we’ve been taking nature apart analytically, when in reality it’s all so much togetherness that it’s really hard to describe.
We’ve been trained to think of each component as a functional component, because that’s the way our brains work. But that’s not really how the system is working. The system is all integrated into a single thing. I think we’re going to learn more and more with these systems biology approaches, how integrated this all is. If we pull something here, something’s going to happen there, and a lot of times, we’re not going to be able to predict what that’s going to be.
AF: I actually see a lot of the same sorts of things that can happen. What both of us are doing is engineering things at a molecular scale, or at the nano scale, or at the atomic level. That’s where the interactions are happening. That’s where everything actually functions.
So you take most battery systems, and what you’ve got is a molecule. Every single one of them practically has an electrolyte, which is just solvent and charged ions, with various structure to that, and various tendency to react with the surface, to transfer, or move in and out of materials, to undergo a redox [reduction-oxidation] reaction. All kinds of things like that will occur universally in these systems. And what we’re doing is engineering the materials that then interact with those electrolyte molecules.
What we’re doing is designing these materials to do the right thing. The complexity that you mentioned, and the interactions that occur, are extremely complicated.
[Various battery system components, each optimized to increase conductivity], are interacting with each other, and having an impact on each other, whether it’s the voltage profile that the device operates at, or in some cases of a lead-acid battery, our sulfuric acid electrolyte actually undergoes a redox reaction, alongside the negative and positive electrode. So there’s a lot of complexity.
Moore’s Law for Batteries?
DC: So how do you design one of these? A lot of times, we use nature as a guide, because we have all these molecules and we say, ‘OK, we want to improve it.’ But how do you go about that because you really don’t have a guide, right?
AF: The good thing is, I guess, we’re not dealing with nature, so in some ways, maybe we have better controls over the actual materials that are interacting. So you can build model systems, where you say, ‘OK, we’re going to change this attribute, we’re going to change that attribute. We’re going to specifically modify the way it functions.’
People are using the beamlines [from particle accelerators] at Argonne and Lawrence Berkeley [national laboratories] to really fundamentally probe what’s happening at the material interface between an electrolyte molecule and a material that you design, and try to really just understand the fundamentals of what’s going on.
You’re building on decades of research and trying to understand what is the mechanism that occurs there. Nature is already this optimized system that you can go and study and see how it works. A battery is not near as elegant, I’m sure, because it’s only had decades of mankind tinkering with it for that optimization to have occurred, but that’s what you’ve got.
DC: If you plotted [battery] capacity improvement over research time, would it be more of a jagged line, or would there be a punctuated equilibrium, where there’s big leaps?
AF: Everybody always hopes that there’s big leaps here and there. In future technology, for instance, people want to come up with a lithium sulfur battery. Well nobody’s deployed this commercially yet, but they’ve been researching it for 10 or 15 years. And everybody will make a lot of noise about it because it’s going to be six times better than the current lithium ion battery. But it’s 10 years out, and so by the time you get to the point where it’s actually ready, people have improved the existing technology to the point where by the time that first lithium sulfur battery is deployed, it’s not a big leap anymore, it’s an incremental change.
So, unfortunately—I think we see this with all kinds of subtle changes—you get 5 percent a year, every year.
DC: Is there a Moore’s Law then?
AF: It’s 5 percent a year.
DC: I was reading about liquid batteries and thought one day it would be really cool if you could take your electric car, you have a nozzle, just like at a gas station, you’d shove it in, and one part would suck out the used battery, another part would pump in charge. Is that a thing, or is it all just going to be taking out a big block?
AF: Some people have actually developed flowable electrodes, which is going to be your used component—that’s the actual material. Electrolyte is a liquid already. The solid portion is the anode, which is coated on foil, and the cathode, which is coated on foil. The challenge with those—they’re all solid materials—so you mean like a slurry or something?
DC: Yeah.
AF: Which could work, but then, your ability to have good electron conductivity in that flowable medium is diminished. Your ability to arrange it and make sure it’s packed into dense space is difficult. Is it possible, could it be out there in the future at some point? I think maybe so.
[Editor’s note: Check back on Wednesday for the rest of The Xconversation.]
