Binary torsional stiffness compliant mechanism

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A demonstration is given of a fully compliant mechanism with binary torsional stiffness. More details can be found in the research paper that is found at

EDIT: Check out an explanation in these videos:
More videos coming soon!

EDIT: The research paper is now open access and can be freely downloaded by anyone at the doi link above.

EDIT: TLDR: It's a spring with close to zero stiffness that can be easily made on the small scale. Applications are for example sensors, surgical tools, energy harvesters, haptic devices, inertial threshold devices, mechanical logic and microrobots.

There have been a lot of comments on and questions about what it is that we are seeing here. So let me try to explain :)

This is a compliant mechanism. A compliant mechanism works by elastic deformation of slender segment, plate springs, instead pin-joints that you find for example in the suspension mechanism of your car. Compliant mechanisms are awesome, because they can be made to have no overlap and no relative motion between components. This is nice, because it reduces friction, thus wear, no need to lubricate, less noise, less vibrations. It reduces assembly, thus cost, no backlash, simplifies manufacturing. This makes them perfect for applications that need to be extremely precise (like super precise positioning), super clean (like cleanroom clean) and makes it relatively simple to make them very very small (like accelerometer sensors in your phone small).

The downside is that they always push back, after all, they are basically springs. This elastic restoring force can mess up energy efficiency, make them oscillate very fast (especially on small scales things start to vibrate fast) and limit how far they can move.

The idea of this mechanism was to make a spring without stiffness that can be made very small! One can get rid of the stiffness by preloading, which is done here with the mechanical switch at the bottom. It preloads the v-shaped plate spring that compensates the stiffness of the rotational stage. It is a torsional stiffness (or rotational stiffness), because the stage rotates around a virtual rotation point where the plate springs intersect.

Why?

Well, it enables us to make sensor that can measure extremely low frequency phenomena very small. Think of measuring the earth tides, variations in local gravity, small accelerations. To make small mechanical energy harvesters. Make micro robots more efficient. Make meta materials. Improved haptic feedback in for example compliant laparoscopic surgical tools and haptic devices. It can be considered a mechanical transistor or and-gate and thus could be used for mechanical computing (this can only be done if they can be made small :) ). You can give sensitive equipment (in the soft mode) a robust transportation mode (in the stiff mode). Think of the forces involved in launching something to space! You can use it as an inertial threshold detector.

And I have seen many more excellent applications in other comments!

Relevant literature is for example the book "Compliant Mechanisms" by Larry Howell and "Design Principles for precision mechanisms" by Herman Soemers is a great reference.
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On a date
Girl: so, what are you into? Any hobbies?
Me: Uhhh, it's complicated

rijaja
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> Locked.
> Only opens when enough force is applied to it.
> Mechanical zener diode.

dylanm.
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Shout out to the algorithm that runs on YouTube's servers, good recommendation

enesdenizli
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Just need fifty million more of these to make my own super slow and labor intensive CPU.

sarcasmo
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Got reccommended. Don't understand anything. Better check comments.

mkai
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"Machines That Bend Are Better!" ~ Veritasium

DirkIronside
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It's like a tension-based circuit breaker.

KalijahAnderson
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I have literally no idea what this means but looks great!

hansvanzuiden
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The first thing I thought of when I saw this is it'd be a great implementation of the sidestick lockout for the Airbus A320. The system is designed so the sidesticks are locked in center when the autopilot is engaged, but one of the methods of release is applying sufficient force to override the lock. Of course, you're supposed to use the button on the stick instead, but it's for situations where you're instinctivly reacting. Great design!

paigashaona
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Hey! Im working with compliant mechanisms too for my master thesis. Would you like to connect?

icvidz
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It's interesting how it immediately looks like its designed to be scaled down. There's something about the proportions that don't look right for a large 3-d object.

infinitelyexplosive
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fun fact is we all who get this kind of recommended videos have the same personality i guess

PhantomizeMC
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I bet he just goes to some random string of words generator and thinks "yeah, I can do that"

koreboredom
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Nobody:
YouTube recommended: Binary torsional stiffness compliant mechanism

throwingallday
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Is that 3D-printed? What printing material you used for it?

TuomoTamminen
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Seems kind of like a circuit breaker before and after being tripped

joshplayseve
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It’s 3am and this feels like a cup of tea for my brain

blackandwhiteful
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One possible application i see for this is interior door locks, especially in old folks homes. the stiffness provides the ability to lock say a bathroom door for privacy, but if theres an emergency a nurse or EMS can force the door just by applying enough force to the handle.

MidasMakeItRain
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This could have an interesting application of a tampering indicator

-Xaverius
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I appreciate the effort put into this. Would you be able to specify a real world use case for a mechanism like this?

ZURAD