Thermally driven folding
Folding can be used for several purposes.
- The range of motion of a (stiff) assembling robot can be way smaller than the final unfolded products
- It can be used to prevent compressive load from braking filigree structures. (anisotropic flexibility needed)
- In metamaterials it can be used to stow away stuff that isn't needed at a specific moment.
- On the makro-scale level it can be used to build large products with small nanofactories. Its easy to make bigger nanofactories though.
There are various kinds of structures subject to folding and unfolding
- 1D girders forming trusswork structures
- 2D stiff platelet structure forming origami like structures
- 2D soft sheet structure - e.g. for stowing them away when not needed
Means for driving the unfolding
Long range force driven self folding
Spring force driven or actuated unfolding
This works at all temperatures. Energetically both the folded and the unfolded state may be stable but preferably nothing in-between. Monostable structures may be used in springy metamaterials.
- Memo material properties ... emulated elasticity
Thermally driven unfolding (one way)
This works best in the deep nanoscale where masses are small. Energetically there must be a single deep energy trench at the target state. (TODO: add image) This folding method is always monostable.
The prime natural example for thermally driven folding is protein folding. Be careful! Don't mix thermal driven folding up with thermally driven assembly (the sticking between complementary shaped proteins that are already folded to their final shape) Thermally driven folding might have some similarities to partially guided thermally driven assembly as described here.
An example for artificial thermally driven folding is maybe the folding of artificial peptoids. There no artificial examples yet (to check) where chains of rectangular/cuboid/cartesian blocks are made to fold by temperature. This should be possible since self assembly was demonstrated with bricks of this size. It may provide another interesting approach to reach the next level of atomically precise manufacturing systems. See: cuboid brick pseudoribosome.
- (TODO: What is the practical size limit above which thermally driven folding? Multi microcomponent structures are probably too big.)
- Is the time to reach an extremely high degree of confidence that the unfolding was completed short enough for practical use?
- Would it make sense to actually heat the assembled but not yet unfolded microcomponents to speed up? (Related: bunching of stages by temperature)
- (TODO: Discuss special case: Folds right after or even while synthesis.)
- Thermally driven folding can be seen as one form of thermally driven assembly
- Folding principles from origami may be usable in self folding structures
- Energetic locking mechanisms
- Indivisible protein like folding block chain
- Ribosome like chain assembly
- nonthermal selffolding & nonthermal selfassembly
Effective concentration for chain-chain-self-interaction (as meeded in the chain self folding process) is higher (and thus faster) than in the case of self finding since any part of the chain can move further away from any other part of the chain than the chains length.