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[0:00]Imagine a world where you never have to worry about running out of charge on your phone or your electric vehicle. Where everything from your pacemaker to your jumbo jet can be powered wirelessly through the air. What if you could light up a room without any wires or batteries? Or run your household appliances by just plugging them into thin air? This isn't science fiction. This is the future that we're creating here at the Walt with Wireless Power Lab at Stanford University. So let's start at the beginning. It was 1820 when Hans Christian Oersted discovered that an electric current creates a magnetic field. This really launched the age of electromagnetism and led to discoveries by Faraday, Maxwell, and many others. In 1891, the great Nikola Tesla gave a lecture in front of a packed room in New York City and lit up a gas discharge lamp from across the stage without any wires. This was the first public demonstration of wireless power transfer. People were amazed and inspired by Tesla's vision of a wireless world where electricity would be broadcast through the air to everyone. Unfortunately, Tesla's vision was a bit ahead of its time. The technology wasn't there yet, and he couldn't get it to work at scale. But a little over 10 years ago, a group of physicists at MIT revisited Tesla's dream and asked the question, can we transfer power wirelessly over a distance efficiently? And the answer was yes. They showed that you could power a 60 watt light bulb from 7 feet away with about 40% efficiency. So let me explain how it works. To transfer power wirelessly, you need two coils that are tuned to the same frequency. So think about how two tuning forks work. If you hit one tuning fork, it will vibrate, and it will create sound waves that will travel through the air and hit a nearby tuning fork. If that nearby tuning fork is tuned to the same frequency, it will resonate and start vibrating itself. Coils work in a very similar way. The first coil will vibrate electromagnetically at a certain frequency. This will create a magnetic field that extends through the air and hits the second coil. If that second coil is tuned to the same exact frequency, it will resonate and start drawing power from the first coil. This phenomenon is called resonant inductive coupling, and it is the key to efficient long-range wireless power transfer. At Stanford, we're building on these early demonstrations and taking wireless power to the next level. Let me show you a few examples of some of the things that we're doing. So one of the challenges with resonant wireless power is that for it to work efficiently, the two coils need to be tuned to the exact same frequency. Unfortunately, when you have something between the coils, or if the distance or the orientation changes, the resonant frequency will also change. This means that the coils will no longer be tuned to the same frequency and the efficiency will drop off dramatically. So we've developed a new system that dynamically tunes the coils in real time to maintain maximum efficiency even if objects are in between the coils or if the distance or the orientation changes. So let me show you how it works. Here, we have a power source, and it's connected to a transmitting coil. We also have a receiving coil connected to a light bulb, and there's a distance of about 3 ft between the coils. And there's nothing in between the coils right now. So the light bulb is on. Now, let's see what happens if I put this metal shield in between the coils. As you can see, the light bulb is still on, even though there's a metal shield in between the coils. And this is because our system is dynamically tuning the coils in real time to maintain maximum efficiency. Now, let's try it with a human body. As you can see, the light bulb is still on, even though my body is in between the coils. And this is because our system is constantly tuning the coils to maintain maximum efficiency, no matter what is in between the coils. This is really exciting because it opens up the possibility of putting these wireless power systems in our homes, in our offices, in our factories, and even charging electric vehicles while they're moving on the highway. So let's move on to the next example. What if you could take wireless power and transmit it to multiple devices at the same time? So we've designed a new system that we're calling a multi-receiver system, which can transmit power to multiple devices at the same time. So let me show you how it works. Here, we have a transmitting coil in the center and two receiving coils on the outside. And as you can see, both receiving coils are lighting up the light bulbs simultaneously. Now, what if we added a third coil? As you can see, the third coil also lights up, and all three coils are getting power simultaneously. And this is really exciting because it opens up the possibility of putting these systems in a room, in a building, and being able to power all the devices in that room without any wires, without any batteries. So let's move on to the next example. What if you could transmit power wirelessly in a completely different way, using a completely different phenomenon? So we've been working on a new technology called magnetic levitation. This technology relies on the fact that permanent magnets when they're arranged in a certain way, can create a magnetic field that can lift objects into the air. And this is a phenomenon that's known as magnetic levitation. Now, we've developed a new system that not only can levitate objects, but also transfer power to them wirelessly at the same time. So let me show you how it works. Here, we have a base, and it's connected to a power source. We have a small LED light bulb, and it's connected to a small coil, and it's also connected to a set of magnets. Now, when I put the LED light bulb on top of the base, as you can see, it lights up and it floats in midair. And this is because the magnetic field from the base is both levitating the light bulb and transferring power to it wirelessly at the same time. And this is really exciting because it opens up the possibility of putting these types of systems in our homes, in our offices, in our factories, and even using them for things like high-speed magnetic levitation trains. So we're going to continue pushing the boundaries of wireless power, and we hope to continue building new technologies and new systems that will enable the wireless world of the future. Thank you very much.