The application of early evolutionary theory and design laws to the reverse engineering of a 100 micron-radius by 20 micron thick long-shafted modular-hooked Universal Foot for frictional probabilistic attachment from Natural biological attachment mechanisms using scanning electro-deposition electron microscopy and Biomimetic principles.
Author and corresponding author: Bruce E Saunders, MEng
Ex-University of Bath
The design of a Universal Foot for micro-robotic purposes allows for the development of a probabilistic attachment device which uses the forces of Nature at a micro-level, where scaling effects appear to dominate the performance of structures. Cladistic methods identify the first three of the group of all probablistic frictional attachment mechanisms in Nature, of cellulose and of insect chitin. A comparison of the group of cellulose long-shafted hooks for tensile breaking stress yields the solution that, in current research, the Arctium minus long-shafted hook is the strongest in direct tensile loading. A further discussion of the relative complexities of the three groups yields the conclusion that it is the single long-shafted hook of the A. minus that most suited for DFM (Design for Manufacture), using SEM (Scanning Electro-deposition Electron Microscopy). Since the A.minus long-shafted hook develops from the bract of the burdock compound flower, it does not exhibit modifications for material efficiency under direct loading, but a uniform shaft diameter over its length suited for the frictional and tensile forces it might endure over its entire length, not just at its hook through direct interference with the substrate as conventional FEA (Finite Element Analysis) packages would have it. The final design is a compound foot of long-shafted hooks, modularised so as to allow versatility and it may be further enhanced by the addition of sub-structures such as follicles to mimic the setae on tarsi, to add to the frictional interference with a substrate or the contact area.
This is a review article of the three papers published in the Springer-Open journal, “The Journal of Robotics and Biomimetics” in a special issue on nano-/micro-robotics under the following titles:
1. A biomimetic study of natural attachment mechanisms—Arctium minus part 1 
2. A biomimetic study of natural attachment mechanisms: imaging cellulose and chitin part 2 
3. Micro-design using frictional, hooked, attachment mechanisms: a biomimetic study of natural attachment mechanisms—Part 3 
This research/design has been entered into the current Buckminster-Fuller Competition 2016
The title of part 3 above displays the underlying theory behind the exploration of the detail of papers 1 and 2. It accepts the viability of using cladistics methods to arrive at a scenario where we can choose the likelihood of a structure surviving the “evolutionary sieve”, to quote Nicklaus et al , over the use of Linnaeus or other classification methods which can be seen as insignificantly better when it comes to evolutionary manifestations of properties and/or structures. In other words they are all imperfect and so it is that the solution must indeed be imperfect too if it is to reflect the true nature of the Natural World.
The use of the hook is a not very interesting thing. But it is also the ideal way to start with the designing of micro-sized (~100micron) objects that can be assembled into machine-like components for manufacture, although they are a little too old for one to understand their development since the designs are based in evolutionary theory, which are utilised in order to identify which structures are viable and of suitable length and strength to be of use to the manufacture of computer circuit boards.
THE THESIS PROPOSAL
This work derives from a thesis proposal: “The Functional Ecology and Mechanical Properties of Biological Hooks in Nature” which led to a dispelling of the myth that an engineer cannot do a biological subject in that the researcher was the first person to use a confocal microscope by virtue of his imaging knowledge. It led to the theory that there is a way of being able to measure the proportional forces being used in the attachment of those mechanisms that could be measured and used to manufacture a hook that would indeed be of use, but not as expected. Of course the first view was that it was unsuitable to measure with current technology as it was then and now it has become possible only through the work of Hirt et al , by their work on SEM (scanning electro-deposition electron microscopy). Now a hook can be manufactured at a 1:1 scale with the specimen that we wish to reverse engineer and that means that we are on the brink of being able to make things that are of use, in the micro-realm (of the order of 10-100 microns in size).
It all begins with the discovery that it was possible to image one of the probabilistic fasteners under laser light, namely the cellulose hook of burdock (Arctium minus). Therefore the work continued with the chitinous growths of the bee and the grasshopper (Apis mellifera and Omocestus viridulus) tarsii . This encounter with luck was able to make true the theory that the use of the microscope could be for the imaging of a specimen and then the transfer of data directly to a layered manufacture device that was suitable, namely the SEM work of Hirt et al . The point of this imaging was to use it to describe the group of probabilistic fasteners as a number, namely one for the hook, two for the attachment mechanism of the grasshopper O. viridulus with two hooks, and three for the double set of hooks, namely A. mellifera with a separating arolium which could make it all seem like they are intended to prove the theory right and not wrong. The chance of being on top of a specimen structure available without travelling is immense as these were all available at the University of Bath which is set in the countryside of Western England. Particularly the burdock which is used (apparently) as the basis of Velcro and therefore presumed to be without fundament and then it seemed better to use it than to use the others (see below), as it will be shown, for the production of a new hook, a multi-use flat structure of multiple hooks that could be used without being entirely known, as per its value and knowledge. i.e. if it is to be the one to be imitated then it needs to be studied more now that it can be manufactured.
[Figure 1 – Burdock seed-pod from ]
Referring to the Figure of the burdock “head” or seedpod, the following is asked of the reader: “Do you think that it can be reproduced effectively as per the table below, from where I have shown it to be a better hook than those of the other four, namely the Agrimonia eupatoria, Circaea lutetiana, Galium aparine, and Geum urbanum” ?
Table 1: Originating structures of long shafted hooks available in the literature.  and .
The aim therefore, is to develop a Universal micro-robotic frictional probablistic attachment mechanism with a performance that can be modelled graphically, using Biomimetic principles. This is called a universal foot after the fact that a human foot is a frictional probabilistic attachment mechanism and because its performance is to be modelled graphically for design, performance, material, quality and other parameters.
The above question is asked because the burdock hook is stronger and not weaker and therefore the best example to be reproduced and hence it is of the best form, whether of cellulose or of chitin since it has a long shaft and an end that is available to the head of a layered manufacturing device. In the end it is a misnomer to think that it could be any more than a reproduction of the shaft that makes it fast and not slow to reproduce since it is of a cellulose hook, not chitin which is a very complicated biomaterial and therefore not easy to reproduce its properties. With cellulose however, it is a known material that has been much studied and therefore it is available to be reproduced via a green theory workplace. Until then we shall make do with copper, not gold, since it is the cheaper of the two and therefore available to mass production and can be seen to be the best fit for the solution of making a reproduce-able hook that will sustain in making it to the end of the product lifecycle. See  again for the details of the imaging and deposition process.
With respect to a Universal Foot it is impossible to sustain it since there is a possibility that it should not hold the right angle on the surface/substrate and that is overcome with a hinge that would allow the foot to align with the ground according to its angle and not the angle of application. It therefore can be used by the military to develop further and so it is about to be since it has application to the frontier of technology and the use is yet to be completely foreseen, such as micro-robotics, biosensors, computer hardware, orthodontics and optical sensors through the use of copper which is a very known substance with qualities that have been researched and ascertained through its use as a strain gauge and other common applications.
It will be seen that there are a number of solutions to the problem of a Universal Foot and that means a test-rig will have to be devised such that it can measure the forces with which a hook attaches to a substrate and that is the way through, to the end of the series such that each member of the group of probabilistic fasteners can be measured, of different biological materials as imaged in . In the meantime it is possible to make deductions such that a design can be arrived at that resembles a caterpillar yet makes use of the hook of the burdock and the range of movement that requires needful thinking so that it can be measured. Once this is done we have a product which can be commercialised.
Part 2  contains the results of the experimentation to image cellulose and chitin and this will prove useful in the future when we consider a wide range of hooking and other mechanisms/devices since it will be in the interest of those continuing the study to know the difference between the two and whether they can use the data to make hooks that are biological such as those to attach to the stomach wall or the vessels of the heart since they bear cilia which makes them difficult to render in a stainless steel such as a stent. But when it is available it may be possible to make them from a biological material which does not dissolve such as the MIT device which, when swallowed, removes a watch battery from the stomach wall to avoid a ulcer forming there or to patch a wound, steered by magnetic fields and which is still in the experimental phase. It is made from pig’s sinew which is insoluble but which does not lend itself to electro-deposition of course so an alternative will need to be found. The electrodeposition of stainless steel has been investigated by Hasegawa et al  and it shows that an improvement has been made to the processing of an otherwise inert steel that does not corrode or “anodize” and it can be electro-deposited on copper .
The result of this entire thesis response has been that there has been interest expressed by a number of causes, namely the Fluids and Aerodynamics Committee of the USA as well as the biomedical field in terms of the development of medical devices small enough not to interfere with the local metabolism and made from a biomaterial like pig’s sinew. Further it can be said that there are numerous persons who have not understood and therefore it is clear that the education of the typical engineer of the present era is lacking.
Figure 2: A zipper configuration in isometric view. This illustrates the possibilities of a composite formation of long-shafted hooks acting a coordinated fashion. The point being illustrated here is that although we are seeking a Universal “foot”, it is as unlikely to look like a foot as a drone looks like a hummingbird from .
The entire result of this PhD research was online for a long time prior to formal publication. It has been warmly received although not everyone appears to have been honest about their sources when they have used the research material to their own ends. This is an anomaly but it is not unexpected. Professionalism is not what it is about these days, it is about theft and under-cutting the competition even where there is none.
It would appear that there is a valid reason for the use of this work to begin a staged assault on the work of Dai, Gorb et al  and other biologists to see if they are accurate with their summations as to the use of live beetles to measure the strengths of attachment of a tarsal group. There is a reason for this. If they are then it is better to expose it to the world as valid. However, if they are incorrect then experimentation should proceed with artificial hooks that are manufactured using the new SEM method and so there should be research available in this direction for a while.
There needs to be a graph laid out of measured performance such that it can be used as a design specification for work in designing at this level. If it is accurate then it will be possible to make use of it to give the resulting designs the go ahead on the case of risk analysis, or manufacturing permissions in the case of quality assurance.
The best way of doing this seems to be through the use of dimensional analysis and the generation of dimensionless groups from an energy equation, namely the la Grange equation used in buckling and extension of structures. This is but a suggestion and needs to be investigated further in a research environment. But it is about time that it was done for the delay of the past few years has set back the work some time.
It is concluded that anything can be manufactured for sale but not always can it be marketed as such. The market for a small hook is likely to be huge, but it is a way of measuring the scaling effects upon a structure due to frictional forces et al that makes it a valuable tool since it is without doubt the simplest to measure with that will make a fundamental difference in our lives as we begin to redesign everything according to the design rules laid down by the new work to be done in measuring the respective forces that make up the new free body diagrams that represent the next generation of manufacture, namely the rule that states that the forces upon all hooks and more complex shapes shall be different from those of greater size.
It will be some time before the commercialisation of these processes occurs but it will also need an avenue of funding if it is to be brought to the British soil as per the engineering hypothesis that all work should be undertaken in the United States or E.U., not China where already there has been some work done through Andrew Parker, PhD. Further material can be found on the use of scaffolds to bind heart tissue together a la Velcro  using bioprinting, a relatively new technique.
- Saunders B E. Biomimetic study of natural attachment mechanisms—imaging cellulose and chitin part 2. J. Robot. Biomim. 2015;2:7. doi:1186/s40638-015-0032-9.
- Saunders B E. A biomimetic study of natural attachment mechanisms – Arctium minus part 1. J. Robot. Biomim. 2015:2:4. DOI10.1186/s40638-015-0028-5
- Saunders B E Microdesign using frictional, hooked, attachment mechanisms: a biomimetic study of natural attachment mechanisms – part 3. J. Robot. Biomim. 2016:3:4. DOI10.1186/s40638-016-0040-4
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