Hello again fancy folks, welcome to Season 3 of LuxeSci, a podcast to reignite your wonder by exploring the science behind luxury items..
As you could probably tell from the last episode, I’m super excited about this season’s topic. Everyone, well, almost everyone wears clothes and there’s a huge industry behind what we wear and how we wear it. The fashion industry revenue was around 1.7 trillion in 2021 (that’s trillion, with a T). For me personally, fashion is what started this whole podcast. I was the girl in the lab wearing heels (closed-toed of course), who dressed up for conferences and who was just as likely to be reading a fashion magazine as a scientific article. This is where my passions collide and we get to take a much closer, like atomically close look at the science behind fashion.
We kicked off the season last week with fashion trends and now we’re transitioning into the building blocks of fashion, starting with fabric. There are two amazing books that will feature prominently in this season, Victoria Finlay’s “Fabric: The Hidden History of the Material World” and “The Golden Thread: How Fabric Changed the World” by Kassie St. Claire. Both of these authors also wrote fascinating books about color that we referenced for Season 2.
While we will get into the molecular structure, producing and dying of various fabrics during the course of the season, I wanted to start off with some really cool science on fabric in general. So today we’ll take a scientific lens to draping, tactile experiences and even some AI-like fabric. It’ll be a little more high-level but still super science-y and super fun.
Background
Of course we need to do a little background/definitions first.
Textile - broad term encompassing fibers, yarns, filaments, threads and different fabric types.
Initial, textile only applied to woven fabrics but has since broadened its definition
Two groups: consumer textiles (clothing, upholstery) and technical textiles (medical textiles, industrial textiles)
Fabric - thin, flexible material made from yarn, directly from fibers, polymeric film foam or any combination of these techniques.
The smallest component of fabric is a fiber
Science
First, I was surprised how many scientific articles are out there having to do with fabric manufacturing. I suppose I shouldn’t have been given how big the garment industry is, but it was still hard to narrow down which articles to talk about. I thought I would focus on 1 article about a fundamental property of fabric, 1 article about how we interact with fabric and 1 article about cool new innovations in fabric. But of course we have to start with definitions.
Textile - originally used to describe woven materials, it now encompasses a wide range of material including fibers, yarns and fabrics
Fabric - thin, flexible material derived from yarn, fibers, polymeric film, foam or a combination. Broader meaning than cloth to include material, cloth, goods, etc
Cloth - flexible substance usually made through weaving, felting or knitting using natural or synthetic materials. Cloth is a type of fabric but not all fabrics are cloth.
For the purposes of this podcast, we will be using the term fabric more generically
The smallest component of fabric is a fiber. Fibers are thin and hair-like and their sources can be either natural or synthetic
They are polymers - macromolecules (large molecules) made up of smaller chemical units (monomers in multiples). Can be natural (cellulose) or synthetic (plastics)
Because of how they assemble, they are tough, have high elasticity and tend to form amorphous structures rather than crystals
Natural polymers are polymers that grow when smaller monomers react and release water or methane molecules or other by products (condensation polymers). Synthetic polymers can either be assembled this way or by addition polymerization which involves monomers with a double or triple bond and results in no by-products
Now that we’ve had a little crash course in fabrics and fibers, how does that fabric get made into a garment?
Draping - If you’re like me and you’ve watched so many seasons of Project Runway, you feel like you can make comments about how garments drape. But what is draping? Simplistically, draping is the way that fabric falls. You could also describe it as “the 3-D deformation of fabrics arising from their own weight”. (If you want to be fancy) While draping is the act of creating a garment without cutting, all garments do have “drape” since all fabric possess this quality.
What is the science behind this phenomenon. It’s (simply) elastic deformations of a thin sheet of material. Interestingly, draping has caused some problems with scientists trying to create formulas for it. Draping is inhomogeneous, meaning that all the fabric won’t drape the same way. Additionally, for anyone who has added pleats to a garment knows, fabrics can equally comfortable in many different configurations. Interestingly, there are some patterns to draping (pun intended). Usually drapes contain flat, cylindrical and conical shapes. Additionally, it takes only a small amount of energy to change drape shapes rather radically. (this is way fabric appears to be moving when you’re walking). All this is rather confounding for scientists trying to come up with a formula for draping.
Article by Zaihuan Mei, et al published in PLOS One in 2015, the authors seek to update how we measure drape.
Why would you want to measure and predict the way that a fabric will drape? Usually, the drape of a fabric is subjective to the designer and/or manufacturer. However, this method lacks reproducibility. If you’re a clothing manufacturer pumping out thousands of garments, you want them all to look the same.
This idea of quantifying the drape of fabric goes back to the 1930s when a method was developed based on 2 parameters, bending length and flexural rigidity. However, this was an estimate at best since drape is a 3-D characteristics of the fabric.
A method developed in the 1950’s called the Fabric Research Liberating (FRL) drape meter introduced the concept of the drape coefficient. This is essentially a function of the test (which uses an optical meter to trace the draped pattern of a circular sample of fabric between two circular plates on a thin piece of paper. That pattern is cut out and weighted to get the drape coefficient). The drape coefficient is the ratio of the projected (Draped) area of the fabric sample to its undraped area. Essentially, how much of the fabric was involved in the drape.
Improvements were made to this technique but still had one major issue, they all measure a 3-D phenomenon with a 2-D process. Additionally, laying the fabric down to drape means that gravity is acting perpendicular to the fabric plane in these types of testing, while in garments, gravity acts parallel to the fabric plane.
So the authors of this paper decided to try to find a better way to quantify drape in fabric. They constructed a set-up with a clamp, a Microsoft Kinect sensor and a computer. They clamped the fabric at one end to produce a unidirectional (and parallel to the plane of the fabric) drape and used the Kinect sensor to created a 3-D image of the draped fabric that could be analyzed for its characteristics
They were able to measure things like peak height, peak width, bending index, etc that allows for a more comprehensive understanding of the draping of the fabric
Who knew there was so much science involved just in how fabric falls?
So we talked a little bit about the science behind how fabric drapes and how to measure that. What about how we, as humans, interact with fabric. We all have our favorites. For example, I’m not actually a huge fan of cashmere. No matter how soft, it always ends up being itchy on me.
Interestingly, science doesn’t fully know how sensory responses work in the brain. What we do know is that touch originates at your skin and then is transmitted through peripheral nerves to the central nervous system for recognition.
The parietal lobe is in the middle part of the brain and is involved in interpreting pain and touch. (aside - it also contains the area of the brain responsible for understanding spoken language)
So how can we measure if people like the feel of a fabric? Historically, questionnaires have been used but these are variable and can be hard to interpret.
A group led by Jiao Jiao published an article in PloS One in 2020 about using Electroencephalographic (EEG) spectra to more subjectively measure how people respond to fabric feel.
EEGs measure brain waves, which are the electrical activity caused by neurons in your brain.
The group took 12 adults, hooked them up to EEGs and had them feel 3 different types of fabric, cotton, nylon and a polyester/wool blend.
They found that differences in EEGs were correlated to how people said they felt about the fabric (so there was a pattern in the EEGs that could distinguish between different fabrics)
While this is cool, i’m not sure about the wider application. Of course, fabric feel is very important for those using prosthetics and such and perhaps for those who can’t voice how they feel, this would be useful. Otherwise, it seems that voiced perception and comfort would be the way to go.
So what’s the fabric of the future? It could be having textile-based robotic wearables. A research group recently published their work in PNAS in 2022 looking at logic controllers made of textiles
Logic controllers - digital computers with programmable memory to store program instructions and various functions (often used in industrial automation)
This team created their computer textile using nylon taffeta fabric coated with thermoplastic polyurethane (making it weather proof). They built it using stacked textile sheets and 2-D sheet-based valves to make the logic controllers to embedded in the fabric
Their textile computer can store data in memory, accept user input, and actuate pneumatic devices
This could be used as an assistance device for people living with disabilities.
That all sounds amazing and very sci-fi, but how about something a little mundane, like getting a hole in your favorite sweater. Now you could go on Youtube or Tiktok how to patch it or perhaps in the future, your fabric will fix itself
Researchers from Bar-Ilan University in Isreal and Harvard Medical School in Boston published research on self-fixing fabrics in Nature’s Scientific Reports in 2017
The researchers grew biofilms from Bacillus subtilis on different types of fabric and chacterized the growth of the biofilm and it’s response to mechanical tears
Biofilm - community of organisms attached to an inert or living surface by a self-produced polymeric matrix or microbial cells associated with a surface and enclosed in a matrix of primarily polysaccharide material
Group of microbes stuck to a surface by sugars
While all the fabrics they used led to microbial growth, certain fabrics were better for the biofilms, including synthetic polyester and cotton with dense weave, cotton with small-sized threads and plain weave and synthetic fabric with large fibers and a loose weave
Next the investigators wanted to see the biofilm’s response to tearing. To do this, they introduced a mechanical tear into the biofilm and looked at the transcriptome (what RNA the biofilm was producing) 5 min after the tear. This would give genes that have been upregulated (expressed) due to the tear. Unsurprisingly, pathways involved in cell wall remodeling and cell division were active in response to the tearing
To test the ability of the biofilm to repair a fabric, genes used for silk production in a species of cricket were inserted into the B. Subtilis bacteria and the biofilms grown and torn. What the researchers saw 5 min after the tear was single fibers being grown from the edge of tear region. This silk protein accumulation occurred mostly along the fabric fibers.
This study was a prototype to test the concept of self-repairing fabric. Clearly more research is needed since the current model would not survive one laundry load. But it’s an interesting concept. We’ve gotten so used to throwing things out when they break and that’s not very sustainable. Given that so much fabric is trashed annually and that growing more cotton involves water and leads to CO2 emission, it would be great to be able to repair more things, like our clothes.
Glossary:
Polymer - large molecules made by bonding together a series of building blocks (Monomers)
Monomer - the building blocks of polymers
Draping - how fabric falls or the 3-D distortion of a sheet as the result of its own weight
EEG - electrocephalographic spectra - visual representation of brain waves based on electricity
Biofilm - thin layer of microbial cells stuck to something by sugars
Transcriptome - set of RNA present in cells that code for proteins
Cocktail Party Facts
One day your clothes may repair themselves because they are embedded with bacteria that will sense when there is a tear and fix the whole by generating new fabric threads to fill the gap.
That’s all for this episode of LuxeSci. I for one, am a bit astounded by how much research goes into fabric. I suppose that’s not surprising since fabric is an ancient material and art and a huge economic driver of today. I am really glad to see some sustainability issues around fabric and fashion being tackled in innovative ways. As always a thank you to my audio engineer and some-times cohost, Dimos. Our theme music is Harlequin Mood by Burdy.
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