- Change materials. There are materials that have metal-insulator transitions, for example, such that it might be possible to trigger dramatic changes in conduction (for switching purposes) with small stimuli, evading the device physics responsible for the subthreshold slope argument.
- Change architectures. Having memory and logic physically separated isn't the only way to do digital computing. The idea of "logic-in-memory" computing goes back to before I was born.
- Radically change architectures. As I've written before, there is great interest in neuromorphic computing, trying to make devices with connectivity and function designed to mimic the way neurons work in biological brains. This would likely mean analog rather than digital logic and memory, complex history-dependent responses, and trying to get vastly improved connectivity. As was published last week in Science, 1 cubic millimeter of brain tissue contains 57,000 cells and 150,000,000 synapses. Trying to duplicate that level of 3D integration at scale is going to be very hard. The approach of just making something that starts with crazy but uncontrolled connectivity and training it somehow (e.g., this idea from 2002) may reappear.
- Update: A user on twitter pointed out that the time may finally be right for superconducting electronics. Here is a recent article in IEEE Spectrum about this, and here is a youtube video of a pretty good intro. The technology of interest is "rapid single-flux quantum" (RSFQ) logic, where information is stored in circulating current loops in devices based on Josephson junctions. The compelling aspects include intrinsically ultralow power dissipation b/c of superconductivity, and intrinsically fast timescales (clock speeds of hundreds of GHz) because of the frequency scales associated with the Josephson effect. I'm a bit skeptical, because these ideas have been around for 30+ years and the integration challenges are still significant, but maybe now the economic motivation is finally sufficient.
A blog about condensed matter and nanoscale physics. Why should high energy and astro folks have all the fun?
Saturday, May 18, 2024
Power and computing
Tuesday, May 07, 2024
Wind-up nanotechnology
Carbon nanotubes are one of the most elastically strong materials out there. A bit over a decade ago, a group at Michigan State did a serious theoretical analysis of how much energy you could store in a twisted yarn made from single-walled carbon nanotubes. They found that the specific energy storage could get as large as several MJ/kg, as much as four times what you get with lithium ion batteries!
Now, a group in Japan has actually put this to the test, in this Nature Nano paper. They get up to 2.1 MJ/kg, over the lithium ion battery mark, and the specific power (when they release the energy) at about \(10^{6}\) W/kg is not too far away from "non-cyclable" energy storage media, like TNT. Very cool!