Steal This Idea: Auto-Temperature Coffee Mug


Steal This Idea is intended to be a series on my blog. Like many of you, I occasionally have these flashes of brilliance, and I’m just going to throw humility out the window and call them genius. Often, I see them on the market a couple years later, so apparently I’m not the only one. I don’t really have time to go execute on all of them though, so I’ve decided to start giving them away, in the hope that someone else who has the resources and the time will.  So by all means – steal this idea!

Several years ago, my wife and I stopped by Starbucks on our way to church, and got our respective beverages in our own insulated mugs (I’m not a coffee drinker, so I just get hot chocolate). As often happens at Starbucks, the drink I received was much too hot to drink. Because I had it in an insulated mug, it stayed at that temperature for a long time. In fact, 20 minutes later when we arrived at church, it was still too hot, and I ended up leaving it in the car and not drinking any of it.

So all through church I’m thinking about how to solve this problem, and what occurred to me is that what I need is a selectively insulated mug – a mug where the insulation can be broken to allow heat to escape, and then reestablish the insulation to hold it at that preferred temperature. What I envisioned were a series of metal ‘tabs’ inside the insulation layer that would expand when heated, and could be calibrated to connect with the metal exterior of the mug at n degrees, and then contract away from the outside when the temperature drops below n degrees. I sketched what that might look like below:

Auto temp mug schematic

Auto temp mug schematic

I’ve spent some time researching what might make this work. Unfortunately, the only things I’ve found that expand and contract substantially in the 100-140 degree range are toxic, like mercury, and something tells me that wouldn’t go over real well with the Starbucks crowd. Chemistry and material physics isn’t really my forte though, so maybe I’m overlooking something.

The other option, of course, is something that doesn’t work automatically, but manually. It wouldn’t be an elegant solution, and would require more attention from the user, but I can envision some kind of mechanical switch which would connect or disconnect the inner and outer layers. You’d just need to occasionally burn your tongue as a test, or integrate some kind of temperature gauge.

Either way, developing something like this is a bit outside my expertise, but I still want this mug. So if this sort of thing is your bag, and you know more about material science than me – please, build me a mug that fixes this. And if you sell it to Starbucks for millions of dollars, send me a 10% cut and I’ll be happy.

Update: My dad turned me on to PCMs (Phase Change Materials) as a possible solution to this, and after research it does look like they would work well for this application. A few weeks after finding PCMs the Fraunhofer Institute released photos of a prototype PCM cup that did just that. So I guess I’m not the only one who’s been thinking about it 🙂