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Mass gatherings, such as major sports events and festivals, bring together people from different regions and countries. One associated risk of such large gatherings is the potential spread of antimicrobial resistance (AMR), a growing threat that undermines the effectiveness of treatments for infectious diseases.

However, it is a threat hard to assess due to the lack of a suitable baseline. The COVID-19 pandemic border closures provided an opportunity to establish a baseline level for antimicrobial resistance genes (ARGs) and show the impact of mass gatherings once travel resumed.

A study, led by Changzhi Wang, a Ph.D. student in Pei-Ying Hong’s group at KAUST, indicates that mass gatherings contribute to the spread of specific ARGs into local wastewater systems[1].

The presence of ARGs in wastewater is a potential cause of concern in Saudi Arabia. In its many rural areas, wastewater is collected in septic tanks that may be leaking into the surrounding environment, rather than being treated in centralized facilities.

The researchers sampled wastewater from four wastewater treatment plants that usually received untreated sewage from mass gatherings, as well as the local community. They also obtained sewage samples from a control plant that does not receive any wastewater from mass gatherings. Sampling was carried out between July 2020 and August 2022, after borders were reopened.

Using metagenomic analysis, the researchers investigated the relative abundance of ARGs, focusing on those conferring resistance to beta-lactam antibiotics, specifically metallo-beta-lactamase (MBL) and extended-spectrum beta-lactamase (ESBL).

“We observed MBL/ESBL families in specific periods that were associated with mass gatherings,” says Wang.

“This is represented by a corresponding increase in the number of meropenem and ceftazidime-resistant colonies recovered from the sewage in the four treatment plants after the mass gatherings in 2022,” he explains.

In contrast, at the control plant, the researchers could not isolate any of these meropenem or ceftazidime-resistant colonies.

“We also detected a beta-lactamase gene (blaPER) in pathogenic bacteria during the peak period of mass gatherings, which reinforces the evidence that these gatherings could introduce new antimicrobial resistance genes to the local community,” Wang concludes.

Their findings have implications for monitoring AMR. They suggest that relying solely on the relative abundance of total ARGs may overlook key human-driven changes in resistance patterns.

The researchers conclude that adopting metagenomics as a surveillance approach, combined with bioinformatic analysis of specific ARGs, may more effectively reveal how mass gatherings contribute to the spread of AMR.

Hong believes the insights are crucial for informing public health strategies to ensure better preparedness and response to the spread of AMR during mass events.

“Based on our findings, wastewater/water surveillance could be an appropriate tool to monitor for a broad spectrum of microbial targets,” she says. “The findings highlight the risk posed by untreated wastewater and suboptimal wastewater treatment infrastructure.”

Hong explains that the study also highlighted the need for integration of omics-based approaches with cultivation-based monitoring methods to more effectively assess and mitigate AMR risks.

“These insights are crucial for informing public health strategies and interventions, ensuring better preparedness and response to the spread of antimicrobial resistance during mass gatherings,” she concludes.

Whether it is an extra X or an extra Y, new research shows that additional sex chromosomes can scramble the genetic script in surprisingly similar ways.

In a first-of-its-kind stem cell study, researchers found that two of the most common sex-chromosome anomalies in males hijack the same genetic pathways[1]. This alters key brain-related genes in ways that could help explain their overlapping cognitive and developmental symptoms.

Led by Antonio Adamo, the KAUST team used patient-derived induced pluripotent stem cells (iPSCs) to model early development in the lab, converting them into neural precursors that preserved the unique genetic makeup of their donors.

The researchers created the world’s first iPSC lines from individuals with Jacobs syndrome, a condition affecting approximately one in 1,000 males, in which boys inherit an extra Y chromosome in addition to the usual X-Y pair. These were compared to iPSC-based models of Klinefelter syndrome, in which males inherit two X chromosomes plus a Y. Notably, participants of Saudi origin were included, broadening the genetic diversity often represented in such studies.

Adamo’s team observed that gene regulation begins to unravel almost immediately in cells carrying extra sex chromosomes — and that these disruptions converge on the same molecular networks, particularly those tied to brain development, hormone signalling, and metabolism. All three pathways are commonly affected in individuals with sex chromosome abnormalities.

The findings suggest that, despite their distinct chromosomal profiles, both Jacobs and Klinefelter syndromes may disrupt genome regulation through a shared mechanism, tipping the balance that normally keeps gene expression in check.

“When cells carry an extra X or Y chromosome, the balance of gene activity is disrupted in a similar way, ultimately affecting the entire genome,” Adamo says. “Our findings highlight the Y chromosome’s unexpected and essential role in regulating the genome, challenging the long-standing view of it as a minor player in human biology.”

Researchers focused on a little-studied gene called UTY, one of the few active genes on the Y chromosome during early development. UTY was predictably overexpressed in cells from individuals with Jacobs syndrome who harbor two copies of the Y chromosome. What surprised the researchers was its apparent influence on KDM6A (also known as UTX), an X-linked gene known to play a critical role in brain development and associated with neurodevelopmental disorders such as autism.

“The two genes appear to be engaged in ‘transcriptional crosstalk,’ with imbalances in either one reverberating through critical developmental pathways, ultimately contributing to the same kinds of molecular misfires seen in both syndromes,” Adamo explains. “Our results both support and refine existing models of how epigenetic mechanisms respond to changes in sex chromosome number.”

Beyond shedding light on the fundamental biology of sex-chromosome aneuploidies, the study also points to a promising therapeutic lead.

“Because UTY encodes an enzyme involved in gene regulation, it offers a rare, actionable drug target in an area of medicine where treatment options remain scarce,” notes study co-author Veronica Astro, a research scientist in Adamo’s group. “Controlling its activity with specific inhibitors might be possible, opening new paths for targeted therapy of sex chromosome aneuploidies.”

People have long been intrigued by the possibility of life beyond Earth and how it might endure in extraterrestrial environments. There is no confirmed evidence of extraterrestrial life, not even on the planetary neighbor Mars. However, an international project led by KAUST’s Alexandre Rosado demonstrates how a particular type of black fungus, known to tolerate highly acidic conditions on Earth, could survive and even thrive in Mars-like environments [1].

“With the current advancement of space missions to Mars, both orbital and robotic, we are closer than ever to answering whether there was, or is, biological activity on the Red Planet,” says Alef Santos, who worked on the project as a visiting Ph.D. student in Rosado’s lab, together with Junia Schultz and co-workers. “Understanding the limits of life in extreme environments on Earth is a crucial step toward interpreting biosignatures beyond our planet. Extremophilic microorganisms that survive and thrive in hostile environments offer valuable natural models for how extraterrestrial life might adapt.”

The team chooses to study the black fungus Rhinocladiella similis based on genomic analyses and previous experimental evidence suggesting that the fungus possesses a robust genetic toolkit capable of withstanding multiple environmental stressors. They are particularly interested in how R. similis might survive in perchlorate salt brines, which are hypothesized to exist intermittently on Mars, along with other environmental factors, including intense UV-C radiation.

At KAUST, the researchers replicate a Mars-like environment in the lab by growing R. similis in a magnesium perchlorate solution under UV-C radiation. They also grow the same fungus under UV-C only. Analysis of the metabolic and proteomic responses of R. similis to magnesium perchlorate shows it exhibits morphological and behavioral changes compared to growth under UV-C alone. These changes include producing protective pigments like melanin and activating proteins associated with stress response and cellular stability.

“That a eukaryotic microorganism, such as a melanized fungus, can maintain activity in a magnesium perchlorate solution — a strong oxidizing agent — is highly relevant when considering the habitability of transient brine systems on Mars,” says Schultz. “Projects like this help refine the search for biosignatures by suggesting metabolic or structural traits that could indicate the presence of life, past or present, on other planets.”

Potential applications of these results extend beyond the search for extraterrestrial life. Schultz adds: “The study provides a proof of concept for space biomanufacturing: the use of microbial systems to produce pigments, enzymes, or other compounds under extraterrestrial conditions. For instance, fungal melanin could be studied for its radiation-shielding properties.”

On Earth, applications abound in bioremediation, helping to detoxify polluted environments, especially in arid and semi-arid regions where perchlorate accumulation is a growing concern. Fungi like R. similis could be used in biotechnological innovations, including the development of enzymes for industrial processes that require high tolerance to salinity or oxidative stress, such as wastewater treatment.

“This research also holds strategic importance for Saudi Arabia and the broader Middle East — a region characterized by extreme environments that can serve as terrestrial analogs for Mars,” says Rosado. “Saudi Arabia is uniquely positioned to lead in astrobiological research grounded in local biodiversity. Understanding extremophiles such as R. similis helps us expand the conceptual boundaries of habitability.”

A moisture-absorbing polymer-based composite, or hydrogel, is set to enhance solar panel efficiency and lifespan, offering a scalable, low-cost solution for hot and humid environments. The material, developed at KAUST, absorbs ambient moisture overnight and provides cooling by slowly releasing water throughout the day[1].

Solar panels are central to the clean energy transition, accounting for most renewable additions worldwide and reducing nearly 1.5 billion tons of carbon dioxide emissions annually. Discoveries of new materials and improved manufacturing techniques are crucial for this continued progress, as they enhance solar panel performance.

A key challenge for solar panels is that, alongside converting sunlight into electricity, they also absorb light as heat. This thermal buildup raises panel temperatures, reducing power output and shortening operational lifespan. Existing cooling systems designed to manage these effects often rely on external power sources to circulate water or air — an approach that is both energy-intensive and costly. These systems also require frequent maintenance.

To design a cheaper and greener alternative, a team led by Qiaoqiang Gan and postdoc Saichao Dang has created a hydrogel layer that uses natural evaporative cooling. Attached to the rear of solar panels, the layer operates autonomously, requiring no electricity or maintenance.

The hydrogel consists of lithium chloride salt embedded in a cross-linked polymer network formed by sodium polyacrylate. Through this microporous polymer matrix, the salt helps pull in moisture from the air. The polymer network contains tiny pores that trap water molecules and includes hydrophilic carboxylate groups, which further enhance water storage capacity.

“Each component plays a role,” says Dang. “By adjusting their proportions, we found a sweet spot where the gel can hold enough water and release it slowly throughout the day.”

Researchers fabricated the hydrogel using a straightforward process. They stirred the polymer powder into the salt solution for three minutes, poured the mixture into a mold, flattened it, and allowed it to cure at room temperature for one hour.

The hydrogel demonstrated sustained cooling and strong water uptake. In a long-term outdoor test at temperatures ranging from 25 C to 41 C and relative humidities of 31 to 91 percent, it reversibly absorbed and released water over 21 days without failure. At 38 C, it achieved a record temperature drop of 14.1 C, boosting power conversion efficiency by 12.9 percent.

“We expected a slow release but were surprised by how steady and how long the cooling lasted — even under strong sunlight for 10 hours,” Dang says.

Ongoing performance assessments under extremely hot and arid conditions at King Abdulaziz City for Science and Technology (KACST) in Riyadh help demonstrate the hydrogel’s robustness in a real-world desert environment, which mirrors the conditions found at many solar farm sites worldwide, notes Gan.

The cooling system is expected to extend solar panel lifespan by more than 200 percent and reduce the levelized cost of electricity by 18 percent — a significant economic advantage for both residential and utility-scale installations. Gan adds: “We are exploring commercialization pathways to deploy this system in operational solar farms.”

The year is 2050. Sustainably sourced fish and seafood have replaced 70 percent of red meat consumption worldwide, and seaweed is a staple vegetable for millions. Food waste has been reduced by 75 percent thanks to ambitious new laws and behavioral change, and half of all land degraded by unsustainable agricultural practices has been successfully restored.

Is this a pipe dream or a feasible future reality?

These goals are reviewed by an international, interdisciplinary team of researchers, led by KAUST scientists. The team outlines how to meet the proposed targets and achieve the goals of the Rio Conventions by “bending the curve” of land degradation and transforming global food systems[1].

“Land lies at the heart of everything we depend on. It feeds our communities, supports rich ecosystems, and helps keep the climate in balance. But the way we’re degrading land today puts all of that at risk,” says KAUST’s Fernando Maestre. “This damage doesn’t happen in isolation. It fuels a chain reaction of growing global challenges — from food and water shortages to displacement, social unrest, and deepening inequality.”

Feeding a global population of more than eight billion is placing extreme pressure on Earth’s land and aquatic ecosystems. The three Rio Conventions, agreed at the Earth Summit in Rio de Janeiro in 1992, advocate for balanced global systems that protect and sustain the natural world.

While preventing and reversing land degradation is a key goal of the U.N. Convention to Combat Desertification (UNCCD), continued population growth means that global food production will need to increase by an estimated 35-56 percent by 2050.

“Tackling the land crisis while ensuring sustainable food for all demands a strategic, integrated approach that connects environmental health with how we grow and consume food,” Maestre notes. “We need clear targets and actionable solutions.”

The team calls for restoring half of all degraded farmland through sustainable land management practices to reverse decades of soil erosion, nutrient depletion, and the intensive use of machinery, pesticides, and fertilizers — particularly on large industrial farms.

However, smallholdings and family farms, which make up the majority of farms worldwide, often rely on local traditions to keep their land viable. Supporting these farms to diversify, build resilience, and adopt sustainable land management practices at scale is essential. “Empowering smallholder farmers with secure land rights, fair market access, and modern, sustainable agricultural tools can significantly boost their productivity and income,” says Maestre.

The team also proposes restoring half of all degraded non-agricultural land — 9.87 million square kilometers — by 2050. This will require equitable and inclusive engagement with all stakeholders, along with the integration of scientific, traditional, and local knowledge.

With global diets projected to require a shift away from carbon-intensive red meats and processed foods by 2050, the research team recommends substituting 70 percent of red meat intake with fish and seafood, and replacing 10 percent of vegetable consumption with seaweed.

Integrating marine and land-based food production requires careful consideration to avoid transferring environmental pressures from land to sea. Supporting this transition will require financial incentives, investment in infrastructure and transportation of marine foodstuffs, and technological support for local communities. The researchers acknowledge that meat-rich diets should be retained in lower-income countries and for specific population groups to ensure overall health and nutrition.

Currently, one-third of all food produced each year is wasted, representing US$1 trillion in losses and the use of 1.4 billion hectares of land. To reduce food waste by 75 percent by 2050, the KAUST-led team calls for coordinated efforts across both production and consumption. These include banning contracts that require aesthetically pleasing fruit and vegetables, investing in long-term storage solutions, and encouraging farmers to grow crops suited to local environmental conditions.

Maestre adds: “To tackle the land crisis and feed a growing population, we need a united, strategic approach that connects how we use land with how we produce food. Strengthening cooperation between global environmental agreements should drive bold action.”

Miniature LEDs called micro-LEDs have been shown to generate random numbers at gigabit-per-second speeds by a team of researchers from Saudi Arabia and the United States[1].

The generation of random numbers is vital for many tasks, including data security — where it is used to create encryption keys and passwords — and computer simulations of complex systems such as the weather and financial markets.

There is, therefore, a strong demand to develop cost-effective random number generators that are small enough for chip-scale integration while also offering a fast generation rate.

The most robust and reliable way to generate true random numbers is to sample and digitize a physical process underpinned by the intrinsic randomness of quantum mechanics. For example, the thermal noise, chaos, and jitter from electronic and optoelectronic devices have all been investigated in the past.

Now, Heming Lin, Boon Ooi, and coworkers from KAUST, King Abdulaziz City for Science and Technology (KACST), and the University of California at Santa Barbara report that intensity fluctuations in the spontaneous emission from blue GaN micro-LEDs, ranging in size from 5-100 μm, can serve as a quantum random number generator (QRNG) with an ultra-high generation rate of 9.375 Gbit/s.

“Micro-LEDs are compact, reliable, and cost-effective,” say Lin and Ooi. “They consume less power and require simpler electronic and photonic system architectures than other competing technologies.”

The idea of using LEDs to generate numbers is not new. Over the past decade, research teams have explored measuring photon number and arrival time. However, a major limitation of these previous schemes is that they have provided much slower generation rates, typically on the scale of no more than a few hundred megabits per second.

“Systems relying on single-photon detection typically extract only two bits per sampling cycle, whereas our system achieves six bits by leveraging intensity fluctuations,” explain Lin and Ooi.

Importantly, for any QRNG to be trusted, its output must be stringently tested to ensure it is sufficiently random. The tests developed by the U.S. National Institute of Standards and Technology (NIST) are the gold standard. The KAUST team tested a variety of micro-LEDs with different sizes — spanning from 5 × 5 μm² to 100 × 100 μm² — and drive currents ranging from 0.5 to 100 mA. All passed the NIST tests.

The team’s future work will focus on boosting generation rates by creating 2D arrays of micro-LEDs that enable parallel random number generation.

The researchers are also planning to create a fully integrated system, rather than using discrete components. At present, the KAUST system comprises a GaN micro-LED, which is temperature stabilized using a thermoelectric cooler and has its light emission fed to an avalanche photodetector. This, in turn, is connected to a sampling oscilloscope via an electronic amplifier.

Lin and Ooi add:“Our next step is to integrate an on-chip photodetector with the micro-LED and subsequently incorporate all the required electronic components to realize a fully integrated QRNG chip.”

From soft robotic fingers that can gently grasp and release delicate objects on demand to luminescent water quality monitors that dim to signal the presence of contaminants, numerous smart devices could be derived from a rapidly developing new family of stimuli-responsive molecular materials called porous cages.

“These stimuli-responsive molecular entities enable us to make smart materials that can automatically respond to cues or changes in their environment,” says Niveen Khashab from the Smart Hybrid Materials Lab at KAUST. As a pioneer in stimuli-responsive porous cage research, Khashab was invited to share her expert perspective on this rapidly emerging field[1].

“Porous cages are discrete, hollow molecular constructs that can accept small molecule ‘guests’ within the cavity at their core,” she explains. Hosting a guest molecule triggers structural and property changes in the porous cage, enabling useful functions such as movement or color change. “Our key contribution to the field has been the design and synthesis of molecular hosts capable of recognizing a wide range of guest molecules, and thus responding to changes at the molecular level.”

Khashab adds that this work has led to smart gels and pastes with applications ranging from smart agriculture to wound healing.

Unlike other guest-hosting materials such as metal-organic frameworks (MOFs), a key advantage of porous cages is that they dissolve easily in organic solvents, which enables their ready incorporation into various devices. In the dissolved state, porous cages can be coated onto surfaces, mixed into other materials such as plastics, or directly cross-linked to create smart materials with a dynamic, stimuli-responsive coating or core.

The potential to develop sophisticated devices from such materials drew Khashab’s two co-authors, postdoctoral researchers Peiren Liu and Fang Fang, to join her lab. Fang says: “What intrigued both of us was the possibility of integrating molecular cage host–guest systems with polymers, thereby translating molecular-level responsiveness into tangible, macroscopic functional behaviors.”

Liu and Fang co-led the lab work on the team’s latest contribution to the field, novel urea porous cages, which they combined with a polymer to create a stimuli-responsive film. When exposed to organic vapors, the two ends of the film curled up toward each other as guest molecules from the vapor were absorbed by the film. The team used this material to build soft robotic fingers that grasp and release objects in response to specific vapor cues.

The KAUST team’s perspective article highlighted advances from across the field. These developments included porous cage membranes with switchable permeability for chemical purification applications, as well as porous cages decorated with a light-emitting sidechain that underwent a shift in light emission along with the absorption of specific guest molecules — such as common contaminants in water supplies.

“The potential applications of porous cages are diverse,” Liu says. “I think the most exciting real-world uses for such materials lie in soft robotics — particularly in developing artificial muscles — and in wearable devices for environmental monitoring and healthcare.”

When water drains from the bottom of a vertical tube, it is followed by a thin film of liquid that can adopt complex and beautiful shapes. KAUST researchers have now studied exactly how these “fluted films” form and break up, developing a mathematical model of their behavior that could help improve the performance, safety, and efficiency of industrial processes[1]

“At first glance, water draining from a tube seems like an everyday process driven by gravity,” says Abhijit Kushwaha, a member of the team behind the work. “It is only with high-speed imaging that we can slow down time enough to capture the hidden choreography of this process.”

For the study, the team used hollow tubes of varying diameters, filled with water to different heights. As the researchers allowed the water to flow out, a high-speed camera captured the shapes formed over a period of about a hundred milliseconds.

This revealed a curious effect for certain combinations of tube diameter and water height. As the liquid fell, a thin film of water dragged against the tube walls and descended more slowly. Once the main water column exited the tube, this film emerged and formed a fleeting, tulip-shaped bubble. In some cases, the fluted film quickly retracted into the tube; in others, it stretched until the water column broke away from it.

The formation of fluted films depends on a delicate balance of gravity, surface tension, inertia, and viscosity, explains Kushwaha. If the water column is too short or the tube is too narrow, the film does not form. Conversely, the widest tubes produce a cylindrical film that breaks away from the tube to create a crown shape.
The researchers created a mathematical model to predict the behavior of these films based on a few simple parameters, such as tube radius and water height. “This can inform better design and control strategies in any system where thin liquid films play a vital role — from industrial reactors to microelectronics to biological systems, such as the lungs,” explains Tadd Truscott, who leads the research.

For example, devices called falling-film evaporators are widely used in industries like food processing, pharmaceuticals, and power generation to concentrate liquids or remove solvents. These systems feature thin films of liquid that evaporate as they flow down the walls of heated tubes. If these films break or become uneven, heat transfer efficiency can be reduced, or equipment can be damaged.

“Our research helps improve understanding of when and how such films might rupture or behave unexpectedly, offering insights that could be used to design more reliable systems,” Truscott says. “This could also be relevant to cooling rocket engines or applying protective coatings to surfaces.”
The team plans to study how other fluids behave in a broader range of tubes. “Ultimately, our goal is to develop a predictive framework that helps scientists and engineers understand, design, and optimize systems where thin films play a hidden but crucial role,” Kushwaha adds.

KAUST bioengineers have developed a flexible optoelectronic patch, or ePatch, that is worn on a patient’s skin and can continuously monitor blood pressure without the need for compressible cuffs or wired devices [1].

Continuous blood pressure monitoring could offer significant benefits across multiple health conditions, helping both patients and medical professionals. Deterioration in conditions such as cardiovascular disease and diabetes could be caught and treated more quickly if there were a comfortable, real-time method of monitoring blood pressure throughout patients’ daily lives.
“Wearable electronics enable 24/7 monitoring and deliver comprehensive data for health analysis without patients needing to attend multiple medical appointments,” says Yizhou Zhong, who worked on the project under the supervision of KAUST’s Sahika Inal as part of an international team from KAUST that included scientists from the United Kingdom, United States, and Spain.
The thin-film patch integrates multiple components to provide accurate blood pressure readings. Its robust polymer substrate houses various functional elements, including an organic electrochemical transistor, an organic photodiode, LEDs, and biosensor electrodes.

“Our breakthrough moment was achieving simultaneous measurement of two critical types of physiological information in a combined hybrid signal,” says Zhong.

Existing blood pressure monitoring relies on electrocardiography (ECG), which measures heart rhythm and rate. At the same time, blood volume changes in microvascular tissues are determined using photoplethysmography (PPG), which involves shining light into the skin and measuring the amount of light transmitted or reflected back. This enables calculation of blood transit time from the aortic valve to peripheral sites. The new ePatch integrates these two signals into a single hybrid signal, known as an electrocardio-photoplethysmogram (EC-PPG).
“The transistor collects signals from both the PPG-recording photodiodes and the ECG electrodes, combines them, and then amplifies the output so that we can resolve the signals properly. This is unique to our design,” says Zhong. “The EC-PPG data is then analyzed externally via a deep learning model to estimate blood pressure.”
“This is a tool with very exciting potential,” adds Inal. “Our approach enables continuous monitoring at 10-second intervals and outperforms existing dual-signal approaches. Separately, biosensor electrodes in the ePatch also measure sweat ion and glucose concentrations — vital signs unrelated to blood pressure but useful metrics in cardiovascular health assessment.”
The ePatch also reduces hardware expenses, and computational demands are low because the deep learning models are trained on a single hybrid signal. However, the manufacturing process is currently time-consuming, so the researchers need to optimize it before the patch can be mass-produced.
The team is planning several ePatch improvements as it moves into prototype trials. Further miniaturization and encapsulation will enhance user comfort and durability, while integrating a compact, efficient power source will support long-term, self-powered operation.

“We also hope to incorporate a reliable wireless communication interface that will improve real-time data transmission and offer consistent remote monitoring capabilities,” concludes Zhong.

 

 

Stylolites — irregular seams that occur in limestone — have been found to affect how acoustic waves move through rock samples. Laboratory-based insights from KAUST researchers offer an improved understanding of how these features impact acoustic imaging techniques, which are used to analyze induced microseismic events during hydraulic fracturing[1].
Carbonate-based sedimentary rocks like limestone often hold gas and oil reserves within their layers. Researchers commonly use sound (acoustic) waves to interrogate subsurface rocks and identify rock types, reservoir size, and internal sedimentary or structural features that influence fluid flow.
“Sedimentary rock layers are rarely uniform. Stylolites, for example, are serrated discontinuities that run through carbonate rock and result in visible, jagged ‘boundary layers,’ often at oblique angles to bedding,” says Thomas Finkbeiner, who led the study in collaboration with colleagues and former KAUST postdoc Bing Yang from Three Gorges University in Yichang, China.

Stylolites mark dissolution surfaces where minerals from the host rock have been dissolved by large overburden stresses. The resulting boundary consists of reprecipitated, insoluble material, such as clay. Due to their mechanical contrast with the host rock, these discontinuities may disrupt sound waves as they pass through.

The finding came from a stroke of luck for the researchers. “We were using limestone blocks for another experimental lab study when we noticed that stylolites were present in our samples,” says Finkbeiner. “This inspired us to investigate their physical properties in more detail and find out how they influence acoustic wave propagation at the lab scale. Few studies have explored stylolites from this angle before.”

The team imaged the stylolites using X-ray tomography equipment to gather data on their three-dimensional morphologies and characterize their dimensions.

“Imaging these stylolites was tricky because they were rather thin and had geometrically very irregular surfaces,” notes Finkbeiner. “Also, to better understand how their mechanical properties contrast with the ambient host rock, we had to open up our rock specimens with a saw, chisel, and hammer to access the stylolites and measure their hardness.”

The researchers recorded acoustic wave velocities and amplitudes passing through the rock samples. They fed the acquired data into a computer model that simulated sound wave propagation through the rocks at frequencies appropriate for lab-scale specimens.
The results showed that stylolites are weak discontinuities that exhibit minimal influence on the first arrivals of transmitted acoustic waveforms. However, they significantly affect coda waves — secondary waves that form due to scattering from small-scale variations. This impacts the overall soundwave energy transmission through the rock.

“With increasing stylolite thickness, acoustic waves scatter more strongly and introduce more noise into the wavefield,” says Finkbeiner. “In laboratory experiments, this has implications for monitoring hydraulic fracture propagation in rock samples that contain stylolites. Our results will help determine the best way to locate acoustic emissions inside lab-scale rock samples.”

The researchers are now conducting larger rock block tests. They use advanced fiber optics detection and refined data processing techniques to see whether these findings can be scaled up and repeated.