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Thank you!

No I actually didn't have muscle fibers in mind -- there's quite a bit of ongoing research specifically in that area.

Yes!

The catch is any notch you make will weaken the material significantly and you'll have fatigue failures. That's the sneaky part of using a flexible sleeve, you don't introduce any undesired weaknesses.

Thanks!

I did experiment with various ways of allowing light to escape but nothing came close to the properties of a total air gap. You can actually measure (relative) bend angle with it like a protractor since the attenuation is very linear!

There is already existing work that uses colored segments for something similar but those techniques are hard to do outside a well equipped lab.

I didn't include this in my article but I did some experiments early on (for a different idea) with air bubbles in oil inside a Teflon coated tube but that presented a lot of challenges (mainly the bubble breaking up) that made it not ideal for something like this.

This can certainly be miniaturized with the right manufacturing techniques but I left that for the future.

I used it more for future-proofing in case I wanted to do sensor fusion or something like that later on -- currently it's just 1D filtering so I could have used anything. Also I'm just way more familiar with using Kalman filters so it was also a comfort thing!

Since the sleeve is a stretchy rubber as long as the inner diameter of it is a bit smaller than the outer diameter of the fiber it holds just fine. For more dynamic applications, though, a silicone adhesive, or even super glue for more permanent strands, helps!

There are a lot of cool applications indeed! I was able to use it to do gait for a soft robot "leg", but I have to wait for the paper to be published later this year before going into too much detail.

There are a lot of similarities in the approach to the linked paper (which is a very cool concept) and I saw a lot of similar concepts in my lit review. At a high level, my sensor targets bend localization with simple fabrication techniques while the linked paper is doing more general camera-based gesture recognition. I have a more thorough comparison to existing work in my actual dissertation.

Our lab has done a good bit of work around elastomers similar to the linked paper, such as multitouch pressure sensing (https://ieeexplore.ieee.org/abstract/document/9674750). The authors of your linked paper can actually achieve what they've done with a single light source by using one of these! The zones are key (https://www.st.com/en/imaging-and-photonics-solutions/time-o...)

Great ideas! Even though I haven't implemented it fully it is possible to sense multiple bends because each bend will always have the same relative attenuation (across the strands) so it would just be a matter of matching on the relative deltas from one reading to another. The catch, though, is at that at some point no light will reach the end if every joint bends a lot. There are ways to mitigate that, but my comment is too long already!

I explored FBG sensors early on and they are very cool -- I was aiming for a less expensive and more robotics-oriented application. Something that can be seamlessly integrated into a design at a lower level without the complexity of FBG technology.

Fixed -- thanks! And yes exactly! I had access to basically any piece of equipment I could want (including a cleanroom that can create ICs) but then basically no one would be able to recreate what I would make.

Thanks!

The short answer? Weekly meetings with my advisor! Long answer: I also had 2 years of classes but I started working on my research immediately, while taking classes. By the time I finished all my classes and became a candidate I had one paper already published and another one accepted, so I was able to get a 3rd paper out and defend by the end of the 3rd year.

I was aiming for significant attenuation when bending, so scratching wouldn't be enough.

Thank you!

3D printing does affect the light passing through significantly. There are a number of options for fabricating these but most of the successful ones involve cutting (can even use a laser cutter).

The finger bending example is certainly a classic for something like this but I think it truly shines in soft robot examples like flapping wing robots or swimming finned robot, where it's critical for sensors to be mechanically transparent so as to not impact the usually delicate dynamics. The "soft" robotic arm in my earlier paper is another good example https://ieeexplore.ieee.org/document/9763962

Haha this made me laugh -- thanks!

Oh yeah cable companies have long been able to do that - I wasn't trying to compete with or replace that technology. My work was soft robotics-focused with simplicity in mind.

Indeed! How do you know her?

Yeah initially doing literature review was a bit daunting because of all this existing work, especially FBG-type sensors, but this idea is so fundamentally simple that its been mostly bypassed by the smarter minds

Thanks -- I definitely relied heavily on my wife in order to maintain that pace.

Thanks!

My (former) school is actually already in the process of doing that! My dissertation committee thought it was novel enough that it needed some IP protection and encouraged me to pursue that.

Very much so!

It doesn't! I heavily used TPU to drive home the point that it can work with almost any light-transmitting fiber. I used PMMA optical fiber for the more fine demos.

Good point -- I need to better explain what "bend localization" means on a more practical level pretty early on.

Ghidra...