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I’m currently working on a special five evolution project taking place on a Europa-like moon orbiting a rogue planet. Under this ice is an ocean 40-60 mile deep with an extensive biosphere fed by kinetosynthetic organisms. A primary way predators find prey is through electroreception. One clade of fish-like animals have a beak made of quartz obtained through eating kinetosynthetic organisms (kinetosynthesis used tiny quartz crystals for piezoelectric charge to fuel reactions). Instead of simply releasing it within their excrements like most creatures, they use it to form a beak. This beak can be snapped shut with high velocity, not dissimilar to snapping your fingers (muscles tighten and a latch releases to snap the beak shut). This snapping would give a small electric burst, distracting the predator and allowing the fish to escape. The major problem is that quartz is a lot more brittle than I had originally assumed, and the beak keeps cracking or even shattering with the forces applied.

My question is, is there a way to make a quartz crystal stronger while still retaining piezoelectric properties? If possible it should be able to withstand 150 megapascals as that was my calculated force.

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  • $\begingroup$ you can't the peizoelectric effect requires the stress, if you reduce the stress you reduce the effect. $\endgroup$ Commented Jan 22 at 2:25
  • $\begingroup$ @john I’m not an expert in this field, but wouldn’t the tensile strength be increased, not the force decreasing? $\endgroup$ Commented Jan 22 at 2:40
  • $\begingroup$ I believe you're needing the compressive strength, rather than tensile - unless the rebound causes the fracture, is that the case? $\endgroup$ Commented Jan 22 at 2:55
  • $\begingroup$ @escaped dental patient I got them completely mixed up. It would be the force that breaks it, not the rebound. $\endgroup$ Commented Jan 22 at 4:13
  • $\begingroup$ Isn't the compressive strength of quartz in the Giga Pascal range, that should offer plenty of zing to your beak. $\endgroup$ Commented Jan 22 at 14:11

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I am not sure if there is a way to prevent the quartz cristals from breaking and while I try to omit frame challenges when not necessary, here comes another one:
If there is no way to prevent the crystals from breaking, let it happen and do your best to deal with it

When biology isn't able to completely handle some physical stress then it invents ways to deal with the outcome.
Some examples:

  • The teeth of rodents can't be hard enough so that they won't wear off. They evolved to let their teeth grow continuously so that it doesn't matter that the teeth wear off (as a side effect it is even necessary to wear off the teeth).
  • The forces of a shark bite are so strong that it is very difficult to not loose some teeth. Instead of trying to keep their teeth they simply regrow lost teeth and they have enough so that a few temporarily missing teeth don't matter.
  • If you hit something hard then it can easily happen that you get some bone fractures while most of the hand remains okay (quite common for martial artists like boxers). That doesn't matter when the fractures are not too strong and frequent so that the bone can heal over time (usually leaving the previous fracture stronger than before).

If there is no way to prevent that the quartz in the beak breaks

  • Prevent that the beak breaks completely and potentially falls off, e.g. embed the weaker quartz cristals inside of something more flexible structure so that the broken cristals don't fall out or let the broken cristals fall out but make sure that this doesn't happen for all cristals at the same time
  • Find a way to regenerate the cristals, either let the organism heal the broken cristals or simply regrow and replace the broken ones.

With such a regenerative approach it is just the question how often the electric shock can be used in which amount of time.

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    $\begingroup$ you can do what teeth and bone do, make a lattice thats full of holes so no stress fracture can run continously across the lattice. $\endgroup$ Commented Jan 23 at 1:11
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You seem to be thinking in terms of extrusions: e.g., teeth, bones, or shells, where minerals are absorbed by the system and then extruded to leverage their structural/mechanical properties. It might be better to think in terms of inclusions, where minerals are incorporated into cell structures for other purposes, the way birds incorporate magnetic minerals so they can sense magnetic fields for navigation. Your creatures don't need entire beaks made of quartz; they merely need small quartz inclusions which can be squeezed or vibrated to produce this electric charge.

Note that there are terrestrial sea creatures that produce electric charges for sensory input or defense: sharks, electric eels, catfish, rays. You should look into how those guys accomplish that, and then consider whether you could use quartz crystals in combination with one of those mechanisms to get a better effect. No sense reinventing the metaphoric wheel…

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