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From: Jeroen Belleman <jeroen@nospam.please>
Newsgroups: sci.electronics.design
Subject: Re: Electrostatic actuators to move robots legs...
Date: Thu, 12 Sep 2024 14:43:02 +0200
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On 9/12/24 12:34, Jeff Layman wrote:
> On 12/09/2024 10:45, Cursitor Doom wrote:
>> On Thu, 12 Sep 2024 05:00:38 GMT, Jan Panteltje wrote:
>>
>>> Artificial muscles propel a robotic leg to walk and jump:
>>>   https://www.sciencedaily.com/releases/2024/09/240909113111.htm
>>>
>>> quote:
>>>   "
>>>   The actuators are oil-filled plastic bags, similar to those used to
>>>   make ice cubes.
>>>   About half of each bag is coated on either side with a black electrode
>>>   made of a conductive material.
>>>   Buchner explains that "as soon as we apply a voltage to the 
>>> electrodes,
>>>   they are attracted to each other due to static electricity.
>>>   ...
>>>   "
>>> And press the fluid out....
>>> So electrostatic actuators!
>>
>> How does that not violate thermodynamics? You seem to be getting useful
>> power from zero energy.
> 
> How do little pieces of paper defy gravity when you put a charged comb 
> near them? Isn't the energy supplied by rubbing the comb against some 
> material to give it the charge to attract the paper? Where does the 
> voltage come from which is applied to the bag electrodes?
> 
> Didn't we discuss something like this not too long ago, or was it in 
> another NG?
> <https://en.wikipedia.org/wiki/Electrostatic_motor>
> 

That was right here in s.e.d in July. And no, thermodynamics, or
rather conservation of energy is not violated. It never is.

I don't think that they can get useful amounts of work out of these
things. The Science Daily article is useless, as always, and I did
not bother to read the paper.

Jeroen Belleman