Bell-bottoms today, miniskirts tomorrow: Math reveals fashion’s 20-year cycle

Scientists create — and mine — most comprehensive fashion database to date

Northwestern University

FacebookXLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Example of how the researchers measured features like hemlines, waistlines and necklines in archival sewing patterns.

view more 

Credit: Emma Zajdela/Daniel Abrams

Fashion insiders and beauty magazines have long cited the “20-year-rule” — the idea that clothing trends often resurface every two decades. 

According to Northwestern University scientists, that observation isn’t just anecdotal. It’s a mathematical reality.

In a new study, the Northwestern team developed a new mathematical model showing that fashion trends tend to cycle roughly every 20 years. By analyzing roughly 37,000 images of women’s clothing spanning from 1869 to today, the team found that styles rise in popularity, fall out of favor and then eventually experience renewal.

Along with supporting common perceptions about the life cycles of fads, the researchers say these results could help explain how new ideas spread in society.

The study’s lead author Emma Zajdela will present these findings at 4:30 p.m. MDT on Tuesday, March 17 at the American Physical Society (APS) Global Physics Summit in Denver. Her talk, “Back in Fashion: Modeling the Cyclical Dynamics of Trends,” is part of the session “Statistical Physics of Networks and Complex Society Systems.”

Complimentary registration is available for members of the media. Press should contact the APS media teamfor more information.

“To our knowledge, this is the first time that someone developed such an extensive and precise database of fashion measures across more than a century,” Zajdela said. “We have some very interesting results, including that the cycle we uncovered in the data (20 years) matches industry knowledge. Historically, the lack of data posed a barrier to explicit quantitative study of this system.”

When this work was conducted, Zajdela was a Ph.D. candidate at Northwestern’s McCormick School of Engineering, where she was advised by Daniel Abrams, a professor of engineering sciences and applied mathematics at McCormick and co-director of the Northwestern Institute on Complex Systems. Now, Zajdela is a postdoctoral fellow at Princeton University and a research fellow at the Santa Fe Institute.

Zajdela and Abrams coauthored the study with Alicia Caticha, an assistant professor of art history at Northwestern’s Weinberg College of Arts and Sciences, and Jeremy White and Emily Kohlberg, who were both members of Abrams’ research group.

To conduct the study, the researchers compiled one of the most comprehensive quantitative datasets of fashion ever assembled. Drawing from historical sewing patterns from the Commercial Pattern Archive at the University of Rhode Island and runway collections, the team analyzed tens of thousands of garments dating back to the late 1800s.

Using custom tools, they measured key features of dresses — hemline, neckline and waistline positions — turning clothing designs into numerical data that could be measured and tracked across decades. To analyze the data, researchers built a mathematical model based on a simple idea: the tension between wanting to stand out while still fitting in. Once a style becomes too common, designers move away from it — but not so far that the clothes become unwearable.

“Over time, this constant push to be different from the recent past causes styles to swing back and forth,” Abrams said. “The system intrinsically wants to oscillate, and we see those cycles in the data.”

The results revealed a striking pattern. While fashion evolves gradually over time, the rise and fall of styles follows a repeating wave that peaks roughly every two decades. One of the clearest patterns involves hemline length. Over the past century, skirt lengths have repeatedly shortened and lengthened — from shorter flapper dresses in the 1920s to longer, more conservative styles in the 1950s and then to miniskirts of the late 1960s.

But this pattern loses its clarity in recent decades. Starting in the 1980s, the data show a wider range of skirt lengths appearing at the same time, suggesting that fashion trends are becoming more fragmented. Rather than one dominant trend, niches emerge, reflecting more diversity in fashion.

“In the past, there were two options — short dresses and long dresses,” Zajdela said. “In more recent years, there are more options: really short dresses, floor-length dresses and midi dresses. There is an increase in variance over time and less conformity.”

 

Representative dresses from 1923 to 1987, showing the change in hemlines over time.

 

Representative dresses from 1920 to 2010.

Credit

Emma Zajdela/Daniel Abrams

 

Turning sawdust into fire-resistant materials

ETH Zurich

FacebookXLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

The researchers’ new material, based on mineralised sawdust, is an excellent fire retardant.

view more 

Credit: Dan Vivas Glaser / from Kürsteiner R et al. Chem Circularity 2026, CC BY 4.0

Every time a tree trunk is sawn, it creates sawdust. Millions of tonnes of sawdust are produced every year worldwide, with most of it is burned to generate energy. This releases the carbon dioxide stored in the wood back into the atmosphere – which is not ideal from an environmental perspective. Now, a team of researchers at the Chair of Wood Materials Science at ETH Zurich and Empa has developed a process that can convert sawdust into a recyclable and environmentally friendly composite using the mineral struvite, a crystalline, colourless ammonium magnesium phosphate. This, in turn, keeps the sawdust in the material cycle for longer. 

Struvite has long been known for its fascinating fire protection properties. Previously, however, it had proven difficult to combine the mineral with sawdust particles due to its crystallisation behaviour. Now, ETH researchers are using an enzyme extracted from watermelon seeds to control the crystallisation of struvite from an aqueous suspension of the mineral precursor Newberyite. This process creates large crystals that fill the cavities between the sawdust particles and bind them together firmly. The material, which is pressed for two days, is then removed from the mould and dried at room temperature. 

Wood elements that protect themselves  

“The material is stronger under compression perpendicular to the grain than the original spruce timber,” explains Ronny Kürsteiner, who developed the process as part of his doctoral thesis. The new material’s mechanical properties and excellent fire resistance make it particularly suitable for internal fittings. That’s because struvite is not only non-combustible, it also helps to actively increase fire resistance. When heated, the mineral breaks down, releasing water vapour and ammonia. This process absorbs heat from the surrounding environment, producing a cooling effect. The non-combustible gases that are released also displace the air, hindering the fire from spreading further and causing the material to char more quickly. 

The ETH team partnered with researchers at the Polytechnic University of Turin, who tested the material in a so-called cone calorimeter – a standardised test that simulates how a material behaves when exposed to an external heat source. While untreated spruce ignites after around 15 seconds, the struvite sawdust composite takes more than three times as long. Once ignited, a protective layer of inorganic material and carbon forms quickly, protecting the material from further fire spread. “The struvite sawdust panels essentially protect themselves,” says Kürsteiner. 

Initial estimates have shown that the material could achieve the same fire protection class as conventional cement-bonded particleboards, although larger-scale flame retardancy tests are still required to confirm this. Cement-bonded particleboards are currently widely used in interior fittings for flame protection applications. They contain 60 to 70 per cent cement by weight, making them heavy and giving them a poor carbon footprint due to the high level of energy involved in cement production. The struvite sawdust board, on the other hand, contains just 40 per cent binder, making it significantly lighter.  

Easy to recycle 

Another advantage of this innovative composite compared to other composite building materials is that, unlike cement-bonded particleboards, for example, it doesn’t end up as waste after demolition. Once removed, the struvite sawdust board can be broken down into its individual components by breaking it up mechanically in a grinder and heating it to just over 100°C. This releases the ammonia and allows the sawdust to be sifted out. After dissolution of the reclaimed material, the precursor newberyite is then precipitated again as a solid. 

Newberyite can then be mixed with sawdust once more to form the struvite composites. This new material could therefore be an important contributor to the circular economy in the future. It can also be used as a natural fertiliser, which has interesting implications for agriculture because it releases the bound phosphorus that plants need for growth in a slow and controlled manner. 

Next, the researchers intend to continue optimising and scaling up the production process. Whether the material will catch on in the construction industry depends primarily on the cost of the binder, says Kürsteiner. Struvite is relatively expensive compared to polymer binders or cement. This could change, however, if they can tap into another cycle: struvite accumulates in large quantities in sewage treatment plants, where it clogs the sewage pipes. “We could use these deposits as a raw material for our building material,” says Kürsteiner.  

Reference

Kürsteiner R, Vivas Glaser D, Ritter M, Parrilli A, Garemark J, Maddalena L, Schnider T, Dreimol CH, Carosio F, Burgert I, Panzarasa G: Enzyme-mediated consolidation of lignocellulosic materials with a flame-retardant and fully recyclable mineral binder. Chem Circularity 2026, 100004. DOI: 10.1016/j.checir.2025.100004

---

Journal

Chem Circularity

DOI

10.1016/j.checir.2025.100004 

Article Title

Enzyme-mediated consolidation of lignocellulosic materials with a flame-retardant and fully recyclable mineral binder

 

SAVE WATER SHOWER WITH A FRIEND

Changing shower and toilet habits could help close England’s 5 billion litre water gap, Surrey-led research finds

University of Surrey

FacebookXLinkedInWeChatBlueskyMessageWhatsAppEmail

Changing how people shower, report leaks and flush toilets could help close England’s projected five billion litre daily water shortfall – but only if the water sector builds the evidence base to make it work, according to a new report led by the University of Surrey. The report has been published to coincide with World Water Day on Sunday 22 March.

The report, Promoting domestic water efficiency via behaviour change, draws on input from more than 100 professionals across 60 organisations in the UK water sector, gathered between October 2024 and April 2025. It was co-authored with researchers from Swansea University, the University of Bristol and the University of Portsmouth.

England currently uses an estimated 135 to 150 litres of water per person each day. Smart metering – the main tool in the government’s demand-reduction strategy – is projected to save around 450 million litres by 2050. According to the Environment Agency’s national framework, 60 per cent of the projected deficit must be recovered through demand management, and researchers believe that means changing behaviour at home.

Professor Benjamin Gardner,  lead author of the report and Director of the Habit Application and Theory group at the University of Surrey, said:

“The water sector knows that behaviour change matters, but it needs to do more to connect with what we know around how people use water. Most initiatives so far have focused on increasing motivation to save water. That approach has its limits – particularly when the behaviours in question are habitual. People do not consciously decide how long to shower, for example. They simply do it, the same way, every day. Telling people how many litres of water they are using is unlikely to change that.”

Sector professionals rated reporting or fixing in-home leaks, showering and flushing toilets as the three most important behaviour change targets. Showering typically uses between six to 15 litres per minute, and a quarter of all drinking water used in UK homes is used to flush toilets. Four of the six highest-priority behaviours identified were bathroom-based.

The report found a significant tension – sector professionals ranked showering and toilet-flushing as critical targets yet placed relatively low value on understanding why people shower or flush. The report argues this is the wrong order of priorities – effective behaviour change depends on understanding what drives a behaviour before attempting to change it. Many water-use habits are automatic and persist even when people want to act differently, because routine, distraction and fatigue prevent conscious adjustment.

Dr Pablo Pereira-Doel, co-author of the study and Director of the Human Insights Lab at the University of Surrey, said:

"We know from our own research that real-time feedback during a shower, delivered at the moment the behaviour is happening, can meaningfully reduce how long people spend under the water. That kind of intervention works precisely because it does not rely on people remembering to act differently. It meets them in the moment. What this report shows is that the sector needs to invest in understanding those moments far more systematically, across all the behaviours that matter, before it can design solutions that will actually stick."

The research also identifies a structural problem – many water companies have conducted relevant behaviour change research but are not sharing findings, largely for commercial reasons. The authors argue that standardised behavioural science tools could allow the sector to share insights without disclosing commercially sensitive details.

The report makes five recommendations:  

• Water sector organisations should work directly with behavioural scientists
• The sector should invest in understanding how people use water, to develop better ways to try to change it
• Water-reduction initiatives should focus on disrupting habits rather than simply educating people about how much water they use
• Knowledge on how to save water should be shared more actively across organisations
• Behaviour change should be treated as just one approach among several, alongside structural and technological solutions.

The report is published by the University of Surrey’s Institute for Sustainability and is available open access at https://tinyurl.com/surreywaterefficiencyarcreport.

[ENDS]

Notes to editors

• Prof Benjamin Gardner is available for interview; please contact mediarelations@surrey.ac.uk to arrange.
• The full report can be found here: https://tinyurl.com/surreywaterefficiencyarcreport

---

Article Title

Promoting domestic water efficiency via behaviour change

 

Direct nervous system link promises more natural leg prostheses

Chalmers University of Technology

FacebookXLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Decoding motor intentions directly from within peripheral nerves may enable more natural and intuitive control of prosthetic limbs. In the study, researchers successfully interpreted signals from the sciatic nerve of above-knee amputees with high accuracy using AI-based spiking neural networks that mimic biological neural communication. The results represent a step towards neurally-controlled prosthetic legs, which could also restore the user’s sensation. The next step is to test the method on real prostheses. Illustration: Pietro Comaschi

view more 

Credit: Pietro Comaschi

A research team led by researchers at Chalmers University of Technology in Sweden, has, for the first time, successfully decoded leg movements directly from the remaining nerves in people with above-knee amputations. Using novel implantable neurotechnology and an AI method based on the nervous system’s own “language”, the researchers could do what was previously impossible and interpret detailed movements – even the will to wiggle toes. This technology opens the way to future leg prostheses that feel and act more like a natural part of the body.

Helping amputees regain a functional and independent life through prostheses that the user can control has long been a major goal in biomedical research.

Currently, arm and hand prostheses are often controlled via the amputee’s remaining muscles, which are still activated by nerve signals from the brain. However, this requires that the relevant muscles are still intact, making muscle-based control impossible in cases of major amputation. For leg amputees, prosthetic legs typically rely on mechanical systems and built-in sensors which automatically adapt to walking without any active user control.

In a new study published in Nature Communications, the research team focused on making more direct use of the nerve signals that remain active post- amputation.

“When you tell your body to move, signals travel through the nerves to the muscles which carry out the action – even if the limb is no longer there,” says Giacomo Valle, assistant professor at Chalmers and one of the study’s senior authors. “This means you can find all the information needed within those nerves. The major challenge is extracting that information and understanding the neural code behind it – and that’s been the focus of our work.”

Reading signals directly from nerves

According to Valle, the ability to read and interpret movement signals directly from within nerves is key to developing future prostheses that are more responsive and intuitive.

“If an implant can be connected directly to the remaining nerves, instead of through residual muscles, you can use exactly the same natural signals used to move your limbs. It greatly increases the potential to create prostheses with natural control, sensory feedback* and unprecedented resolution,” he says.

However, extracting nerve signals directly from the remaining nerves of amputees is extremely challenging. Very few studies have been successful, and all have focused on the upper limbs – even though most people living with amputation have lost a leg. The research is complicated by the fact that the remaining post-amputation nerves produce weak signals that are difficult to capture reliably.

The research group has succeeded in meeting this challenge with a completely new approach focusing on leg amputees, in which the key role is played by a neurotechnological implant, combined with a new, AI-based algorithm.

The same type of neural implant (developed at the University of Freiburg) has been used in previous prosthetic research, but only to stimulate the remaining nerves and restore touch sensation. In this study, the researchers also succeeded in using the technology to read nerve signals in a precise and controlled manner.

In the next step, the researchers employed a new, AI-based technique to interpret the recorded nerve signals. The technique is based on so-called Spiking Neural Networks (SNNs), which differ from conventional AI systems (such as those used in for example ChatGPT or image recognition) by processing time-based signals known as “spikes,” rather than continuous numerical values.

According to Elisa Donati, professor at the University of Zurich and ETH Zürich and the other senior author of the study, these signals therefore mimic more closely how biological neurons communicate.

“Our study shows that decoding peripheral nerve** activity works best when it respects the language of the nervous system,” she says. “Peripheral nerves communicate through discrete electrical impulses – or spikes – and spiking neural networks are therefore naturally suited to processing this type of signal. By aligning our computational models more closely with biology, we can extract movement intent efficiently, using compact models and relatively limited data. This is an important step towards low-power, fully implantable systems for more natural control of prosthetic limbs.”

Decoding intended movements and restoring touch sensation

In the study, the researchers concentrated on above-knee amputations, carrying out tests on two participants. Four ultrathin neural implants – each about the size of a human hair and both flexible and pliable – were inserted into the tibial branch of the sciatic nerve, which plays a central role in driving leg movement and sensation. When participants were asked to attempt different movements with their “phantom leg,” the researchers recorded the outgoing nerve signals and decoded them with unprecedented high resolution using their AI-based algorithm.

“This is the first study to demonstrate that signals recorded directly from peripheral nerves can be used to accurately interpret intended leg movements in amputees,” says Valle. “With this approach, we were able to map specific nerve signals to specific movements and predict, with high accuracy, which movements the participants were attempting.”

The method provides the opportunity to interpret very specific leg movements for the knees, ankles and toes – even those that were previously impossible to decode.

“The study provides unique insight into how the nervous system transmits information. We’ve cracked the code of nerve communication and shown that it’s possible to interpret detailed leg movements, even in amputations where most of the leg is gone. It was amazing to see how electrodes placed high up in what remains of a leg could decode attempts to wiggle the toes,” Valle says.

According to the research group, another advantage is that the technology can be used for both motor control and restoring sensation, with a single implant. Until now, several different implants have been required for prostheses to be able to both “move” and “feel”.

“The system is bidirectional,” explains Valle. “Once electrodes are implanted inside the nerve, they can be used to communicate bidirectionally with the nervous system. So, for the first time, a single neurotechnology can provide both natural neural control and sensory feedback in the same implantable device.”

Next step: integrating the technology into a prosthetic leg

The study is a “proof of concept“, demonstrating that the technique is feasible. The next step is to test it on real prostheses. While the findings are particularly significant for the development of prosthetic legs, Valle believes the method could be extended to other types of prostheses in the future.

“I believe these results could significantly influence the field. The next step is to integrate and test the technology into a prosthetic leg that can be controlled directly and that can return natural sensation,” he says.

*Sensory feedback is the information that the brain constantly receives from the body’s sensory organs about the state of the body and the environment. It is the brain’s way of “feeling” what the body is doing and where it is, which allows us to interact with the world smoothly and safely.

** Peripheral nerves are nerve fibres located outside the brain and spinal cord.

More about the research:

The study Decoding phantom limb movements from intraneural recordings has been published in Nature Communications. The authors are Cecilia Rossi, Marko Bumbasirevic, Paul Čvančara, Thomas Stieglitz, Stanisa Raspopovic, Elisa Donati and Giacomo Valle. The researchers are affiliated with Chalmers University of Technology, Sweden, the University of Zurich and ETH Zürich, Switzerland, the University of Belgrade, Serbia, the University of Freiburg, Germany and the Medical University of Vienna, Austria.

---

Journal

Nature Communications

DOI

10.1038/s41467-026-69297-0 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Decoding phantom limb movements from intraneural recordings

Article Publication Date

8-Feb-2026

COI Statement

G.V. holds shares of “MYNERVA AG”, a start-up company dealing with the potential commercialization of noninvasive stimulating wearable for treating neuropathic pain. G.V. serves as a consultant for NeuroOne Medical Technologies Corporation (USA). The other authors do not have anything to disclose.