Wishful Thinking

Yesterday, I ran across an article touting “The World’s Thinnest Circuits” and out of habit, mentally consigned it to my ‘interesting reference for product development’ stack. But later I was climbing and thinking about where SFT could go after a couple of shoe models (perhaps early for such speculations, but this is how motivate myself on days that mostly involve paperwork):

If I had super thin circuits,

film super capacitors,

a distributed sensing (or a brain-computer interface),

and digitally reconfigurable materials,

then SFT shoes could adjust themselves.

Let’s unpack my wishlist. Super thin circuits are on their way, but why do I want them? In a couple projects I’ve seen, flex cables and flexible circuit boards were a blessing and a curse. They’re the only system that can enable certain designs, but their bend radii (at least 20 times the material thickness for dynamic applications) can start to drive a design. So from this perspective, thinner electronics are great, provided that the bend radius-to-thickness ratio remains similar or improves.

Physical design is gated by power storage solutions even more than it is by circuitry. My basic rage at batteries is due to the fact that their power density is pitiful, they have to be protected like precious eggs, and their form-factors are not nearly varied enough. Definitely looking forward to when thin-film supercapacitors, like this transparent one, can store useful amounts of energy and are cost-effective. So let’s pretend we’ve got that.

A brain-computer interface might be asking too much (though Ms. Jepson disagrees), especially since it would be much slicker to let the shoes sense what state they should be in, rather than the wearer needing to consciously direct them. Distributed sensing could mean a simple GPS and some microprocessors or the ability to pair with a phone. Both could draw data from a user-populated app like Strava that would tell the shoe, “you’re in Yosemite, and you’re not gaining a lot of elevation, so you’re probably bouldering.” On the other end of the spectrum, the shoe might be laced with strain gauges and EMG sensors, which would provide data to gently relieve strain on foot muscles during a climb.

Which brings us to the last item on the wishlist: digitally reconfigurable materials. Everything described above is useless if the shoe cannot change in the real world and in real time. There is lots of potential with materials like piezoelectrics or Nitinol, but since I have to wait for further development on energy storage systems, digitally reconfigurable materials better make some advances in the intervening time too.

My ultimate desire would be to sandwich the electronics, power source, sensors, and actuators in the fabric of a SFT shoe (maybe made of Tyvek, to balance the added weight of the tech) and let it make adjustments while my feet are on the rock. But that’s so overdesigned for just a climbing shoe that maybe I should skip straight to designing exoskeletons. If Hugh Herr gets to change his height while climbing, I want extra endurance built into all my clothes.


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