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Osaka, Japan – Many structures in biology are bounded by membranes, but not all of them. Droplets of a liquid called a coacervate, which form when oppositely charged molecules come together in water, have attracted attention as models for membraneless compartments inside cells and for “protocells,” hypothetical primitive cells that may have preceded modern ones. Cells today, in contrast, are enclosed by lipid membranes whose behavior is governed by bending elasticity. What happens when these two worlds meet—when a liquid itself is shaped into a membrane—has remained largely unexplored.
In a study published recently in Physical Review Letters, researchers from a multi-institutional team led by the University of Osaka measured, for the first time, how such a lipid membrane bends and fluctuate.
“We know that the behaviors of liquid interfaces and membranes are governed by different physical laws,” explains lead author Rintaro Takahashi, “but we did not know how a membrane that is a liquid would behave.”
To answer this question, the team used a well-established system: vesicles formed by mixing two oppositely charged block copolymers, each consisting of a charged segment and a neutral segment, in water. In these vesicles, the membrane itself is made of a coacervate, so the structure has a membrane-like shape while its interior remains liquid-like. The team then measured the motion of these membranes using a technique known as neutron spin echo spectroscopy, which tracks how structures fluctuate spontaneously on nanometer and nanosecond scales.
“We found that the liquid membrane was able to bend 100 times more easily than lipid membranes,” reports Rintaro Takahashi. “We also determined that the processes driving the bending elasticity were different. The restorative force after bending deformation for the liquid membrane was entropic in origin, in contrast to the enthalpy-driven processes of lipid membranes.”
The study reveals how a membrane made of liquid behaves, a regime intermediate between liquid interfaces and elastic membranes. The findings could help researchers understand how liquid-based compartments, including those proposed as protocells, behave when they take on membrane-like shapes.

Two oppositely charged block copolymers (left) spontaneously assemble in water into hollow spheres called vesicles (center). The magnified view (right) shows the vesicle membrane, in which a liquid coacervate layer is sandwiched between layers of neutral polymer chains.

The article, “When liquids form membranes: entropy-dominated bending dynamics in coacervate vesicles” was published in Physical Review Letters at DOI:
https://doi.org/10.1103/vl6b-y5gz

Related links

• Laboratory of Macromolecular Solutions, Department of Macromolecular Science, Graduate School of Science, The University of Osaka 

• Associate Professor Takahashi Rintaro
• Professor Terao Ken
• Eurkalert!
• AlphaGalileo
• Asia Research News
• ResOU（Research at Osaka University）website

The symposium opened with welcoming remarks by Prof. Tadashi KONDO, Dean of the Graduate School of Science, UOSAKA, followed by introductory presentations on both institutions. Oral sessions in the morning and afternoon were conducted in parallel at two venues—the Nambu Yoichiro Hall and the Sigma Hall—where research outcomes across a wide range of fields were shared, including mathematics, physics, chemistry, biological sciences, macromolecular science, and earth and space science.

In the afternoon, laboratory tours and open discussion sessions provided opportunities for lively exchanges among researchers and students on prospective themes for future joint research and directions for student mobility. Interdisciplinary interaction was further enhanced during the subsequent poster session. Building on this symposium, stronger networking among participants and further deepening of academic exchange and research collaboration are anticipated.

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Conference Title: 2026 NSYSU × UOSAKA Science Joint Symposium
Date: Tuesday, October 27, 2026
Organizers: Graduate School of Science, The University of Osaka; College of Science, National Sun Yat-sen University
Support: The University of Osaka Global Frontier Research Initiative
Venue: The University of Osaka (Nambu Yoichiro Hall, Sigma Hall, Co-Creation Building B, etc.)

The ISP at the GSS is an intensive research internship for overseas students majoring in the natural sciences and related scientific fields, launched in AY2018. The ISP offers students an opportunity to experience research-centered academic life at the GSS, either by joining a research group or by participating in seminars under the guidance of a faculty member. Thematic studies are conducted under close supervision of host professors through experiments, discussions, and group work with the team members at the GSS. Due to the COVID-19 pandemic, the ISP was cancelled in AY2020, and held online in AY2021 and AY2022. We resumed the ISP in person from AY2023; this year was the eighth time the ISP was held (sixth time as a face-to-face event).

Each ISP student received direct supervision from a faculty member(s) of the GSS and conducted cutting-edge research for approximately 6 weeks. In addition to research activities, the ISP students joined Japanese language café sessions organized by Japanese students of the “Science Buddy(*)” to deepen mutual friendships. The ISP students also participated in an excursion bound for Lake Biwa in Shiga to visit Lake Biwa Museum, Omi Jingu Shrine, and Lake Biwa cruise, and a Student Social Event to get to know more ISP fellow students and current international students in the GSS. In a concluding event, the ISP students presented their research progress at the Nambu Yoichiro Hall, and received an ISP certificate, bringing the ISP to a successful conclusion.

We hope that the ISP students will serve as bridges between the GSS and their home institutions, either as regular international students or as international collaborative research partners with the GSS. In addition, we hope that the international outlook of our current Japanese students in the GSS involved as supporters of the 2026 ISP will be bolstered, fostering their future research activities abroad.

<Program Contents and Schedule of 2026 ISP>

July 15
Dormitory Check-in

July 16
Morning: Orientation 1 at Nambu Yoichiro Hall
Afternoon: Orientation 2 with Science Buddy (*), Toyonaka Campus Tour, Research Group Check-in (meet the supervisor)

July 17
Research activities began in earnest

July 18
Excursion to Lake Biwa in Shiga (Lake Biwa Museum, Omi Jingu Shrine, Lake Biwa Cruise, etc.)

July 21 to 31 (two days in total for each student)
Japanese language café offered by current Japanese students of “Science Buddy” (Students were divided into beginner, intermediate, and advanced courses)

July 24
Student Social Event held at International Exchange Salon (D201) of Science Building

August 26
Final Presentation and Closing Ceremony at Nambu Yoichiro Hall
Farewell Party at Cafeteria La Forêt

August 28
Dormitory Check-out

For more information
Past articles (2025 ISP, 2024 ISP, 2023 ISP)
Click here for more details about the ISP

(*) Science Buddy is a student group which aims to enhance international communication and is composed of Japanese and International students in the Graduate School and School of Science.

This event was organized with the support of the International Exchange Committee of the Graduate School of Science.

<Schedule>
1st session: June 18, 2026
2nd session: June 25, 2026
3rd session: July 2, 2026
4th session: July 9, 2026
5th session: July 23, 2026
All the sessions were held from 12:20 pm to 1:20 pm in room B208 (a lecture room of the Science Building).

<Host>
International Exchange Committee of the Graduate School of Science
Graduate School of Science at the University of Osaka

Please click the link below for more details.
Graduate Admissions

Osaka, Japan – Adhesives are essential in electronics, vehicles, and other products, but they can hinder repair and recycling when bonded parts are difficult to separate cleanly. A research team led by The University of Osaka has developed a prototype light-responsive adhesive that can be selectively detached from an illuminated surface without observable residue. The adhesive film can then be rebonded by heating and reused after a second ultraviolet wavelength helps reset its molecular interactions. This study will be published in Matter & Light.
Conventional photoresponsive adhesives release a bond by weakening or chemically changing the adhesive layer itself. That approach can leave residue on a substrate. Other systems achieve cleaner separation through irreversible light-driven reactions, but the adhesive is then difficult to reuse. The team instead aimed to control only the adhesive-substrate interface while keeping the bulk adhesive intact.
The researchers designed a polymer adhesive with reversible host-guest crosslinks between stilbene and triacetylated beta-cyclodextrin. Inspired by photoresponsive actuators, light-driven changes in these crosslinks alter local surface mechanics, creating “interfacial switching”.
Under UV-A light (365 nm), stilbene photoisomerization weakens host-guest association near the illuminated surface. In the optimized material, peel strength fell by about 45%, allowing selective peeling without observable adhesive residue. Similar switching was demonstrated with PET paired with glass, carbon-fiber-reinforced plastic, Nylon 66, and aluminum.
UV-C light (254 nm) restored host-guest association and adhesion. The light-controlled response was retained through 15 peeling cycles; samples were rebonded by heating without solvent processing. Atomic force microscopy confirmed reversible changes in surface stiffness and adhesion.
By switching adhesion at the interface instead of damaging the adhesive bulk, this strategy could ease disassembly, repair, and recycling of electronic, automotive, and semiconductor components. It also offers a design principle for dynamic polymer interfaces and circular manufacturing.
“We asked whether changing only the stiffness at an adhesive interface with light could allow clean peeling without destroying the adhesive itself,” says senior author Professor Yoshinori Takashima. “We hope this concept will lead to advanced adhesives and support more circular manufacturing.”

Concept and key features of the photoresponsive adhesive developed in this study. Based on the concept of “interfacial switching,” light irradiation selectively changes the elastic modulus of only the adhesive interface, enabling clean, residue-free debonding while allowing both the substrate and the adhesive to be reused. The technology is expected to contribute to the recycling of electronic devices, automobiles, semiconductor components, and other products.

The article, “Interfacial Switching-Driven Photoactuator Adhesives for Selective Peeling and Substrate Recycling,” will be published in Matter & Light at DOI: https://doi.org/10.1016/j.matlit.2026.100094

Related links

• Professor Takashima Yoshinori 

• Takashima Laboratory, Department of Macromolecular Science

• Eurkalert!
• AlphaGalileo
• Asia Research News
• ResOU（Research at Osaka University）website

Osaka, Japan – Biodegradable plastics should be tough enough for use, yet able to break down at an appropriate rate afterward. Researchers at the University of Osaka showed that changing the size of rings threaded onto a biodegradable polymer can tune both its toughness and enzymatic degradation, offering a way to design material lifetimes. This study was accepted for publication in ACS Sustainable Chemistry & Engineering.
Polycaprolactone (PCL) is a biodegradable polyester with potential applications in sustainable materials. However, conventional methods used to improve its mechanical performance, such as blending and copolymerization, can alter the molecular structure and chain packing that govern degradation. It has therefore remained difficult to combine practical toughness with controllable end-of-life behavior. To address this challenge, the researchers investigated whether movable molecular crosslinks could reinforce PCL while allowing its degradation rate to be tuned through molecular design.
The team focused on cyclic poly (phenylene sulfide), c[n]PS, an industrial by-product of poly (phenylene sulfide) (PPS) production. They isolated three ring sizes—c [5] PS, c [7] PS, and c [9] PS – and incorporated them into PCL through solvent-free ring-opening polymerization. As PCL chains formed through the rings, pseudorotaxane-based “movable crosslinks” were created. These rings can slide along polymer chains, helping redistribute stress and dissipate energy.
At 0.5 wt%, c [7] PS nearly doubled PCL toughness while preserving its Young’s modulus and thermoplastic reprocessability. Ring size also strongly affected enzymatic degradation: c [5] PS modestly accelerated degradation, c [7] PS slowed it, and c [9] PS degraded fastest, with no residual film mass after 48 hours. Control samples without movable crosslinks did not show the same ring-size dependence. The results are consistent with a mechanism in which ring size changes polymer-chain mobility and the accessibility of amorphous regions to enzymatic attack.
This approach could help create biodegradable plastics that remain durable during use but degrade at a rate suited to their intended end-of-life pathway. It also upcycles a PPS manufacturing by-product into a supramolecular material, supporting circular use of polymer resources.
Senior author Professor Yoshinori Takashima noted that making materials durable and making them break down quickly may seem like contradictory goals. He hopes to control both so polymer lifetimes can be tailored to different applications.

Cyclized poly(phenylene sulfide) (c[n]PS), a byproduct of PPS production, was incorporated into a biodegradable plastic as movable crosslinkers. Simply varying the molecular ring size enables control over both material toughness and the rate of enzymatic degradation, allowing the material lifetime to be tailored.

The article, “Upcycling Waste Cyclic Poly(phenylene sulfide) as Valuable Movable Crosslinkers for Toughening and Ring-Size-Controlled Enzymatic Degradation of Polycaprolactone” will be published in ACS Sustainable Chemistry & Engineering at DOI:  https://doi.org/10.1021/acssuschemeng.6c05417

Related links

• Professor Takashima Yoshinori 

• Takashima Laboratory, Department of Macromolecular Science

• Eurkalert!
• AlphaGalileo
• Asia Research News
• ResOU（Research at Osaka University）website

Osaka, Japan — Sand, powders, and other collections of visible-sized grains are found throughout daily life, from food and pharmaceuticals to soils and industrial materials. When grains of similar size are arranged regularly, they can form a strong crystal-like solid. Yet what happens inside such an ordered structure immediately before it begins to break has remained unclear.

Researchers at the University of Osaka, Shimane University, and Kyoto Sangyo University have now theoretically identified an unusual pattern of vibrations that emerges just before a crystal made of regularly arranged grains yields. Many vibrational modes soften simultaneously along particular directions, while long-wavelength waves travel more slowly than shorter ones. The findings reveal a possible physical precursor to failure in highly ordered particulate materials.

The team studied a two-dimensional model in which particles were arranged in a triangular crystal and slowly sheared, similar to sliding the top of a deck of cards sideways. By taking advantage of the crystal’s regular structure, the researchers analyzed its vibrational modes mathematically as it approached yielding—the point at which deformation becomes irreversible.

Before shear, low-frequency vibrations were concentrated near the center of wave-number space, corresponding to long wavelengths, as expected for an ordinary solid. Close to yielding, however, soft vibrations extended along two specific directions, forming a cross-shaped pattern in wave-number space. “Soft” means that even a small force can cause a large vibrational response.

The researchers also found a striking change in how waves travel through the crystal. In ordinary solids, sufficiently long acoustic waves travel at nearly the same speed regardless of wavelength. Immediately before yielding, waves traveling along the soft direction instead followed a quadratic frequency-wavenumber relationship; longer, gentler waves propagated more slowly than shorter ones. The number of low-frequency vibrations also increased beyond the level predicted by the conventional Debye law.

The team derived these relationships analytically, including their numerical prefactors, and confirmed similar behavior using another type of interaction between particles. This suggests that the behavior may occur broadly in defect-free, ordered particulate systems.

“Granular materials are familiar, but many aspects of their physical behavior remain poorly understood,” says lead author Fumiaki Nakai. “By studying a simple, regularly ordered system, we were able to describe in detail how it approaches yielding. We hope this work will provide a foundation for exploring more complex effects such as disorder, friction, and energy dissipation.”

The findings provide a foundation for understanding and eventually predicting when and how ordered granular materials and colloidal crystals begin to fail. Such knowledge could ultimately contribute to safer and more reliable handling and design of materials made from regularly arranged particles. Because the study considered an ideal crystal without defects, further work will be needed to determine whether similar warning signs appear in real materials.

Maps of the vibration frequency across wavenumber space. Before shear (γ = 0, left), low-frequency vibrations gather near the center. Just before the crystal breaks (Δγ = 10⁻⁴, right), a cross-shaped low-frequency region appears, showing that the crystal becomes soft along particular directions.

The article, “Anomalous phonon dispersion near yielding in athermal crystals,” will be published in Physical Review E at DOI:  https://doi.org/10.1103/3lnj-1ml1

Related links

• Assistant Professor Nakai Fumiaki 

• Katsuragi Laboratory, Department of Earth and Space Science

• Eurkalert!
• AlphaGalileo
• Asia Research News
• ResOU（Research at Osaka University）website