Living Hinges at the Next Level

First of all, a living hinge is not a biological entity nor does it move on its own. Think of the top of a Tic Tac container where the lid and the cover are a single piece, and the thin plastic holding them together flexes to allow you to reach the candies disguised as mints. [Xiaoyu “Rayne” Zheng] at Virginia Tech designed a method of multimaterial programmable additive manufacturing which is fancy-ese for printing with more than one type of material.

The process works under the premise of printing a 3D latticework, similar to the “FILL” function of a consumer printer. Each segment of material is determined by the software and mixed on the spot by the printer and cured before moving onto the next segment. Like building a bridge one beam at a time, if that bridge were meant for tardigrades and many beams were fabricated each minute. Mixing up each segment as needed means that a different recipe results in a different rigidity, so it is possible to make a robotic leg with stiff “bones” and flexible “joints.”

We love printing in different materials, even if it is only one medium at a time. Printing in metal is useful and could be consumer level soon, but you can print in chocolate right now.

Via Phys.org. Thank you again for the tip, [Qes].

13 thoughts on “Living Hinges at the Next Level

  1. Plastic living hinges like the tic tac lid are amazing. For such a thin little piece of plastic, it always surprises me that they don’t fail after one of two flexes. A sauce bottle or a shampoo bottle can last way longer than it feels like it should.

    The secret is that when they are manufactured, the long chain molecules that make up the polymer are compressed at the hinge which causes them to be oriented straight, strengthening the hinge.

    https://i1.wp.com/www.efunda.com/designstandards/plastic_design/images/hinge1.gif?zoom=2

    1. I hate though when I buy something thats not throw away and intended to last that has a living hinge. I have a lot of various storage/part/component boxes with tape holding the failed living hinge together.

    2. I am not a fan.

      I wish more soaps and shampoos were sold with screw tops, not those plugs on a living hinge.

      The gym I go to has soap in the dispensers that smells like it was made with some sort of dairy product and left out too long. It is nasty! I always try to bring my own bottle of body wash for the shower. But.. sometimes I forget to put it in my bag. I would love to just leave it in the bag. I have other bottles for home, this one is only for the gym anyway. But… if it was sitting there in my bag 24×7 I just know that at some point it would end up upside down or stepped on and that silly cap would pop loose spilling soap all over my bag. If it were a screw on cap I could trust it to stay!

      Down with living hinges!

      1. Most of those bottles are a plugs on a living hinge built as part of a screw top. Why not glue those caps down and unscrew them when you are ready to use the contents?
        I know it’s an extra step, but you should feel safer with the bottles in your bag.

        1. They need to sell them with screw-on tops over top the living-hinge top so you get the best of both worlds. Even better if you make the threading for the top of the living-hinge top the same as the bottle so the customer can have a screw on top, a living hinge top, or both as needed. You could even sell the bottled product with “randomly” chosen tops (one type or the other) so you don’t add to the garbabe produced. You could even reduce garbage production even further by selling the tops separate from the bottles with a folded neck with a flat end when new and sealled that tears open and rounds out to its threading, ready for the screw-on top of choice. 🦊

        2. The ones I have seen are usually only a one-turn screw with a wide spot at the end so that it sort of snaps in place. When you unscrew/re-screw it that wide spot keeps getting crushed. It doesn’t take long before the cap starts popping off easily on it’s own.

          i think they do this because having few threads allows them to keep the transition area where there is both bottle and cap short. That means less plastic saving them some fraction of a cent per bottle which counts for something when multiplied by a billion bottles every year.

  2. Instead of printing one living hinge at a joint, this work prints hundreds of living hinges into the lattice infill. Allowing variable stiffness across whole prints. This is way beyond shampoo bottles, bones and joints.

    1. I’m no expert but what about applications in soft robots and other pneumatic ‘artificial muscles’ (when combined with some sort of air bladder since these lattices don’t look like they can be sealed)?
      And what about this idea s a replacement for various couplers out there?

      1. Soft robots is where my mind goes too. Octopus/squid beaks start off soft at the base, and graduate to a hard sharp tip. Soft robots also would benefit from easily variable rigidity – all the stuff i’ve seen so far depend on altering the thickness of the material, or embedding fibres or whatever manually. I feel that this is a pretty big step forward for 3d printing, which will produce all sorts of cool stuff once people start playing with it and seeing what it can do.

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