Introduction
The idea of what a shoe is has remained the same for a long period of time. Let's try something else.
Shoes today are still often very uncomfortable, they easily become nasty, they're annoying to put on and they can even cause injuries. I believe we have accepted what a shoe should be like so we fail to see their flaws.
I wanted to design an improvement by avoiding making any assumptions about what a shoe is, to hopefully not only create a shoe that is good, but rather a shoe that is truly great. Designed for human feet and human lives. This is the result.
Methods
Like all my projects, the process was sort of chaotic; A lot of pondering, a lot of sketching and a lot of messing around. In this particular project I happened to read a lot of research papers because there were a lot of studies made on the topic of shoes and what makes them comfortable.
To perfect the shape of the shoe, I used 3D scanning to get a much better knowledge of how feet looks like, specifically when you put pressure on it. This is possible with a technique called Photogrammetry were you take a bunch of images of the object you want to scan and then the computer calculates the 3D geometry of the subject.
This would optimally have been done with hundreds of feet, but because I had to do this project from home (Covid-19) I only did one, my own.
Venus
I found that the best solution was to get rid of the normal top piece that usually covers the crest of the foot. However, I still wanted to preserve the stability, comfort and protection that you would lose with a traditional sandal.
I did that by letting the foot sink into the sole, to keep a strong border between the foot and the surrounding environment. This also allows the user to get closer to the ground while still letting the sole remain visually thick and solid.
Most of the pressure-related discomfort and pain from ill-fitting shoes occurs in the forefoot and toebox. (1,2) Taking inspiration from medical-grade footwear that has been developed to help patients with chronic lesions, I chose to widen the front section of the shoe to open up for the natural shape of the foot. This seems to have a significant impact of the perceived level of comfort. (2)
For the same reason, I decided to pull the strap backwards to minimize the pressure on the more sensitive areas in the forefoot. I also decided to limit the amount of straps to one, which would also simplify the user experience and visual perception of the shoe.
However, placing the strap so far back caused the front part of the sole to lose contact with the forefoot. This is how I solved it:
When we first put down the foot while walking we begin with the heel which creates a downwards force. The problem with a 90 degree sole is that it creates a lever arm, which in turn creates a torque. This torque is what initially caused the sole to lose contact with the foot.
If we let the outline of the sole have a constant distance to the heel, the point of rotation will always be beneath the downwards force. This will prevent any lever arm to exist, which in turn prevents any torque to be created.
This allows the sole to never lose contact with the foot.
At first I wanted to have a much thicker sole with a clear decline towards the front of the foot, so that the heel has a lot of support. However, after reading through some research literature about running technique and running injuries, I decided to make the sole completely parallel to the ground with a more regularly dimensioned thickness.
While a thick heel may seem intuitively better for the foot, we can see that it changes how we choose to run. Rather than first putting down the midfoot or forefoot, we automatically put down the heel first. The foot can't help dampen the impact force which causes it to be much larger than it would've been otherwise. (3) Not only is this running technique inefficient, it could also potentially cause injuries.
To simplify the user experience, I've chosen to remove any laces on the shoe and replace it with a single elastic strap. Instead of letting the surface fabric take the stress load that is required to keep a constant pressure over the foot, there is an elastic band inside the strap that does all the "pulling".
Materials
Finding the right materials was by far the most challenging part of the whole project since I wanted the shoe to have some very specific qualities. After studying the properties and the feel of as many materials I could find these were the ones I chose:
Note: this is only a proposition, I'm not really qualified to be this specific with materials and manufacturing.
Merino wool
The fabric closest to the skin is fine-knitted Merino wool. Merino wool comes from a special kind of sheep called Merino sheep. Merino wool has thinner and smoother fibers than regular wool which makes it very pleasant to the touch.
It's important that the thickness of the fiber is below 27 micron since wool fibers thicker than that can make it feel itchy.
The Merino fabric has to be separated into parts in order to create the wanted form. It is desirable to minimize the amount of parts to prevent too much stitches as a seamless shape would be visually optimal, but this is not a vital issue.
The figure shows a suggestion about how those parts could be separated but since my knowledge of textile manufacturing is highly limited it would be wise to have this conversation with an expert of this subject.
I have also been looking into the opportunity of 3D knitting this piece and while it definitely seems possible it would probably require some development of manufacturing methods to make it a viable option.
Wool felt
Wool felt can be made from 100% wool which has a set of amazing qualities that I couldn't really find in any other materials. Wool has the ability to absorb and transport moisture away from skin as well as being very breathable. It also has a self-cleaning and antiseptic property which make the material very resistant to smell and dirt.
Wool is also a renewable material and 100% biodegradable.
The idea with the construction is that the air and moisture could move along with the wool and out of the edges.
This would keep the foot very breathable and free from odor even during long walks in high temperature. Not to mention that the entire top side of the foot is open.
Rubber aerogel
The rubber aerogel is a new material with some other unique properties. Regular aerogel is about 99% air while the rest could be out of almost anything. This makes the material extremely light. 2019, the Department of Mechanical Engineering from the National University of Singapore released a research paper on a new rubber aerogel they made from recycled tires with a whopping density of 0.035 – 0.145 g/cm3.(4)
This is around 10x lighter than natural rubber.
While I haven't found any numbers on the material properties for the strength and elasticity, they released a video that showcases them bending and standing on it.(5) Since it's a brand new material, the production process is around 7$/cm3, but I believe this could be dramatically lowered with the development of the real manufacturing process.
TPU
TPU or Thermoplastic Polyurethane is a durable and incredibly useful elastomer with more interesting properties. It's thermoplastic which means it can be melted and remolded, but yet it has a rubber-like feeling and can be created with varying degrees of hardness. Somewhere around Shore Hardness 60A might be appropriate but further prototyping would be necessary to determine the exact hardness. This piece would be injection molded.
One problem that might occur with TPU is yellowing from the sunlight, so it might be necessary to add a protective coating to help the shoe hold its aesthetic appearance.
The underside has the profile of a tilted sinewave, matching the angle of the strap.
All of these parts are then glued together into a single, pure form...
Final words
I would just like to stress the fact that this is only a concept at this point and that there is still a lot of work left to do if this would ever become a real product. I was not able to build any real prototypes of the shoe which would have been crucial to determine the final design. I'm sure there are plenty of things that I could not figure out from pure theoretical reasoning and simple models.
Anyway, thank you for looking through my project and I hope you have a great day :)
Sources
1. Branthwaite, H., Chockalingam, N. & Greenhalgh, A. The effect of shoe toe box shape and volume on forefoot interdigital and plantar pressures in healthy females. J Foot Ankle Res 6, 28 (2013).
https://doi.org/10.1186/1757-1146-6-28
2. Hurst, B., Branthwaite, H., Greenhalgh, A. et al. Medical-grade footwear: the impact of fit and comfort. J Foot Ankle Res 10, 2 (2017).
https://doi.org/10.1186/s13047-016-0184-z
3. Hamill, Joseph & Russell, Elizabeth & Gruber, Allison & Miller, Ross. (2011). Impact characteristics in shod and barefoot running. Footwear Science. 3. 33-40. 10.1080/19424280.2010.542187.
https://www.researchgate.net/publication/254237004_Impact_characteristics_in_shod_and_barefoot_running4 . Quoc Ba Thai, Toh Ee Siang, Duyen Khac Le, Wassim Akram Shah, Nhan Phan-Thien, Hai M. Duong,
Advanced fabrication and multi-properties of rubber aerogels from car tire waste,
Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 577, 2019, Pages 702-708, ISSN 0927-7757, https://doi.org/10.1016/j.colsurfa.2019.06.029.
http://www.sciencedirect.com/science/article/pii/S09277757193054975. Same as the one above, just video:
https://www.youtube.com/watch?v=ms5i-rYpxl4&list=FLBlmE9Liv8HCxIYzIDGuXHw&index=1Get in contact
simon.ljungblahd@gmail.com
