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Comment by doh | Hacker News Reader

I know this is maybe completely out there, but could focused ultrasound be used to heat up food? The current issue with microwaves is that they heat up food very unevenly. I am sure the current cost is quite prohibitive and all. I'm more interested in the science part itself.

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I've got a cyclonic inverter microwave, and maybe it's all just hype, but I'm pretty sure it cooks more evenly. I also usually choose a lower power level, which helps a lot. The power level button is highly underrated.

I am not expert, but my understanding of cyclonic inverters is that they are able to lower power output and thus achieving more even cooking. That also implies slower time. I am more interested in precision while retaining the speed. But it's something I looked into myself too.

Seems like the challenge would be heating the right places. How would you know what food to heat more or less?

Also, ultrasonic transducers today, as far as I know, require essentially direct contact to impart energy. You probably don't want to dip something into your leftovers just to heat it.

Rather than heating food more or less, I care about equally. Couldn’t combination of thermal camera and ultrasonic transducer achieve the goal?

If they indeed need a contact with the object, then obviously that wouldn’t work. But I am not sure why the air molecules couldn’t carry it.

Impedance mismatch and attenuation. The impedance difference between air and the piezoelectric elements of the transducer is too great - this will cause soundwaves to reflect on contact (and thus never leave the element). If some transducer innovation changed that variable, then attenuation would be the next hurdle.

In general a form of couplant (water, oil, some form of gel, etc) is necessary to eliminate air between the transducer and a material in order for soundwaves to pass.

Thanks for the context. That seems to invalidate the idea.

Solid state microwave ovens (that avoid standing waves/dead zones) do exist, they are just very expensive.

Dumping kWs of ultrasound into food would be a bit tricky.

Thanks for putting me on this topic. Will do much more research.

it feels like (as an uneducated outsider) that a microwave could use some kind of spatial awareness (lidar/sonar/whatever) along with beam-forming and array style transmitters to evenly cook something while sampling temperatures remotely.

the size/shape/cost/performance of such a device is left as an exercise to those better suited to execute that kind of artistry than I am.

I keep thinking about this topic for a couple of years now (hence my question). I wonder if combination of new technology could be made into much more useful microwave, even if the cost was not suitable for personal use (at least initially).

The dream is a microwave with "single button" (start/stop) and a temperature scale (lukewarm, warm, hot, boiling) that consistently heats up food correctly and doing so within very short period of time (below 3 min).

There is work done one this. search for: software defined microwave (SDC)

Super cool. Thanks for the suggestion found this [0] but there appears to be more out there.

[0] https://www.hcii.cmu.edu/news/software-defined-cooking-using...

I think an air fryer or toaster oven solves 80% of your problem using off the shelf tools.

The issue is time. They absolutely work better than microwaves, but microwaves are popular precisely because they are just much faster.

Does slapping a chicken count?

https://m.youtube.com/watch?v=LHFhnnTWMgI

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