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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

Formation of lipid domains using triptycene-based lipid mimic

The article, “Triptycene-Based Lipid Mimics for Thermally Stable Membrane Phase Separation,” was published in the Journal of the American Chemical Society at DOI:
https://doi.org/10.1021/jacs.6c05364

Related links

• lecturer Iwata Takayuki (Researcher Directory)

• Namba Lab, Department of Chemistry

• Eurkalert!
• AlphaGalileo
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(a) Rendered image of the developed measurement system. (b) Enlarged view of the t-SPESI unit and the sample stage unit. (c) Photograph of the conventional ion transfer tube. (d) Photograph of the developed ion transfer tube. (ed) Comparison of the signal intensities of NaI cluster ions. In the legend, O and N indicate the results obtained using the ion transfer tubes shown in (c) and (d), respectively, and the numbers indicate the heater temperature.

The article, “Development of a Tapping-Mode Scanning Probe Electrospray Ionization Platform for High-Sensitivity and Long-Term Stability in Single-Cell Mass Spectrometry Imaging of Tissue,” was published in Analytical Chemistry at https://doi.org/10.1021/acs.analchem.6c02386.

Related links

• Associate Professor Otsuka Yoichi (Researcher Directory)

• Mass Spectrometry Group

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Mitochondria are famously known as the powerhouse of the cell, but their functions go beyond energy generation: they also act as signaling centers, helping the cell to sense and respond to trouble. When mitochondria are ‘hyperfused’, i.e., the stressed, abnormally long state described above, they release their genetic material into the cytosol, where the cell treats it as a warning sign in the same way it would treat a virus.

Recent studies have highlighted that mitochondrial DNA and RNA released into the cytosol can activate innate immune signaling. However, how changes in mitochondrial morphology influence the release of mitochondrial RNA (mtRNA) and the resulting innate immune response has remained poorly understood. Researchers from the University of Osaka set out to clarify these mitochondrial mysteries, and their findings have now been published in Cell Reports.

By using cells engineered to lack DRP1 – preventing mitochondria from dividing – the team triggered hyperfusion and explored the subsequent gene activity. The RNA sequencing analysis demonstrated that genes activated during a typical immune response, interferon-stimulated genes, were upregulated. However, when the hyperfused mitochondria were restored to their normal morphology, the expression of these immune-related genes returned to baseline levels.

“We determined that the trigger was mtRNA leaking into the cytosol, activating RNA-sensing proteins, such as RIG-I and MDA5, which also activate when detecting RNA viruses,” explains lead author Tatsuki Yasuda. “Given the evolutionary origin of mitochondria as descendants of ancient bacteria, it is fascinating that mitochondrial RNA can activate the same surveillance pathways that normally detect invading pathogens.”

These results point to other settings where mitochondrial hyperfusion can arise, including some cancers. Exploring existing cancer datasets, the researchers found that tumors with low DRP1 levels showed higher activity of the same immune-activating genes. In the lab, cancer cells with hyperfused mitochondria were more readily destroyed by natural killer immune cells and failed to grow efficiently after implantation in mice, pointing to a mitochondrial route for stronger anti-tumor immunity.

“Our study identifies a previously unknown molecular mechanism linking mitochondrial morphology to innate immune activation,” says senior author Naotada Ishihara. “We hope these findings will stimulate further research into how mitochondrial dynamics regulate immune responses. Because mtRNA release may contribute to cancer as well as inflammatory and age-related diseases, this mechanism could have broad implications across a range of human disorders.”

The team hopes these findings open new avenues for research into mitochondrial biology and innate immunity. By revealing how mitochondrial shape influences immune signaling, the study provides a new framework for understanding not only cancer but also inflammatory and age-related diseases associated with mitochondrial dysfunction.

Mitochondrial hyperfusion triggers innate immune responses.

The article, “Disrupted mitochondrial dynamics activate RNA sensing innate immunity through mitochondrial RNA release”, was published in Cell Reports at DOI: https://doi.org/10.1016/j.celrep.2026.117607.

Related links

• Professor Ishihara Naotada (Researcher Directory)

• Ishihara Lab, Department of Biological Sciences

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

Now, researchers at the University of Osaka have overcome these limitations by developing a multipath synergistic strategy to toughen elastomers. This study has been published in Nature Communications.

Elastomers are polymers that are exceptionally elastic, i.e., they can deform strongly under external stress and revert to their original shape when the stress is removed. However, traditional elastomers are not very tough, as microscopic cracks can cause the material to tear.
Consequently, strategies are employed to enhance the toughness of elastomers by dissipating energy. That is, during deformation, the polymer absorbs mechanical energy and dissipates it by converting it into other forms of energy.

To reduce the likelihood of tears, three types of energy dissipation strategies can be employed.
i) Molecular sliding – Rotaxane molecules are incorporated into the elastomer, which slide and rotate under an external force, redistributing stress across the network and preventing breakage.
ii) Force-induced bond scission – Molecules are embedded in elastomers with “sacrificial” bonds that break under an applied stress, delaying damage to the elastomer.
iii) Chain entanglement – Molecular design is used to introduce structurally well-defined chain entanglements, which allow chains to slide and rearrange tension across the network when stress occurs.

Individual energy-dissipation strategies provide only a limited improvement in elastomer toughness. Although multiple mechanisms have been incorporated into a single material, achieving synergistic toughening by activating them sequentially as the applied stress increases remains challenging.

“We integrated three energy dissipation pathways that become activated in sequence under increasing stress to prevent failure of the elastomer,” explains lead author Xue Li. “Thus, we synergistically combined three toughening mechanisms.”

In this study, the authors introduced ring molecules with sacrificial bonds into an elastomer. Under applied stress, ring sliding occurs in the elastomer first to absorb force. As the stress increases, the rings cleave to form linear chains. Under even higher stress, the linear chains entangle with other chains, maintaining network connectivity and dissipating energy via chain slippage.

This novel strategy can be used to create materials that are both soft and durable, with uses such as tires, gloves, and adhesives. The superior toughness of these materials translates into improved service life and reliability.

Under an applied force, sequential molecular transformations suppress material failure

The article, “Toughening Elastomer via Sequentially Activated Multi-Pathway Energy Dissipation,” has been published in Nature Communications at DOI:
https://doi.org/10.1038/s41467-026-74148-z.

Related links

• Professor Yamaguchi Hiroyasu (Researcher Directory)

• Assistant Professor Kobayashi Yuichiro (Researcher Directory)

• Supramolecular Functional Chemistry Group

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• ResOU（Research at Osaka University）website

Now, researchers from The University of Osaka have reported a new way to bring ancient proteins back to life. The study, published in ACS Omega, has revealed that the developed methodology can help generate ancestral rhodopsins that can be tested experimentally in bacteria.

A wide range of microbes express proteins called microbial rhodopsins, which are embedded in the cell membrane and play a variety of roles, including pumping ions across the membrane or sensing light. Scientists have long wondered how members of this single family can possess such a wide array of functions, with investigations involving analyzing the protein sequences to determine their evolutionary history.

“Rhodopsins all have seven transmembrane domains that are very similar, but their extramembrane domains, which extend inside and outside of the cell, vary dramatically,” says lead author, Haruto Ishikawa. “This makes it very challenging to use standard sequence alignment techniques to trace the evolution of rhodopsin sequences from their shared ancestral proteins.”

To tackle this problem, the researchers analyzed the sequences of two different microbial rhodopsins, schizorhodopsins and heliorhodopsins, using an approach that specifically accounts for insertions and deletions in the extramembrane domains. Based on this technique, they reconstructed ancestral schizorhodopsin and heliorhodopsin sequences and expressed them in bacteria.

“The results were very exciting,” explains Yasuhisa Mizutani, senior author. “Both the ancestral schizorhodopsin sequence and the ancestral heliorhodopsin sequence produced stable, mature proteins in Escherichia coli that had a distinctive color and showed characteristic spectral properties, just like existing rhodopsins.”

Similar to contemporary schizorhodopsins, the ancestral schizorhodopsin showed light-driven proton-transport activity. In contrast, the ancestral heliorhodopsin did not pump ions, consistent with current heliorhodopsins.

“Our findings show that sequence reconstruction that takes insertions and deletions into account can successfully generate full-length ancestral rhodopsins that can be experimentally produced and tested,” explains Ishikawa.

The researchers have made their analytical pipeline, ConsistASR, available for other investigators to use. The ConsistASR workflow could help reconstruct and engineer other ancestral proteins, providing functional insight into protein evolution.

When E. coli cells producing ancestral rhodopsin (Anc-SzR) were illuminated, the pH of the surrounding solution increased. This result supports that the ancestral rhodopsin absorbs light and, like extant schizorhodopsins, transports hydrogen ions (H⁺) into the cells.

The article, “Resurrecting Full-length Ancestral Schizorhodopsins and Heliorhodopsins with Structure-guided, Indel-aware Sequence Reconstruction,” has been published in ACS Omega at https://doi.org/10.1021/acsomega.6c03010.

Related links

• Associate Professor (Lecturer) ISHIKAWA Haruto (Researcher Directory)

• Mizutzni Laboratory, Laboratory for Biophysical Chemistry

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• ResOU（Research at Osaka University）website

They were welcomed by Prof. Tadashi Kondo, Dean of the Graduate School of Science and Atsushi Takahashi, Vice Dean and Chair of the International Exchange Committee, along with members of the International Affairs Committee and related staff. The two sides held discussions aimed at moving toward full-scale implementation of the Double Degree Program (DDP) agreement concluded in June 2024. During the meeting, they shared information on laboratories that already have ongoing exchanges, as well as laboratories in overlapping research fields and areas in which they hope to further expand collaboration.
Taking this visit as an opportunity, both universities confirmed that they will make use of the DDP agreement to proceed with concrete arrangements for student acceptance and dispatch. They also shared various operational issues that need to be addressed in order to implement these exchanges.

Based on these discussions, we will continue to strengthen the cooperative relationship between the two universities and further examine concrete steps toward student and research exchanges, including the DDP.

(Scenes from the DDP signing ceremony:https://www.sci.osaka-u.ac.jp/en/news/9991_1/ )

[Visitors]
Prof. Luisella Celi, Vice Rector for Research
(Department of Agricultural, Forest and Food Sciences）
Prof. David Lembo, Vice Rector for International Relations
(Department of Clinical and Biological Sciences）
Prof. Federico Maria Petrucci, Rector’s Delegate for Humanities and Social Sciences Strategic Research
(Department of Philosophy and Education Sciences）
Prof. Stefania Maria Beolé, Rector’s Delegate for Natural and Life Sciences Strategic Research
(Department of Physics）
Mr. Stefano Palmieri, Press Office
Ms. Mariasilvia Ciola, Rector’s Advisor for International Projects
Dr. Ugo Falciola, Head of Commercial Office, the Consulate General of Italy in Osaka

[The University of Osaka]
Prof. Tadashi Kondo, Dean, the Graduate School of Science
(Department of Earth and Space Science)
Prof. Atsushi Takahashi , Vice Dean and Chair of the International Exchange Committee
(Department of Mathematics)
Prof. Hajime Nanjo, Member of the International Exchange Committee
(Department of Physics)
Prof. Nobuto Yoshinari , Member of the International Exchange Committee
(Department of Chemistry)
Prof. Yasuhiro Funahashi, Member of the International Exchange Committee
(Department of Chemistry)
Assoc. Prof. Osamu Urakawa , Member of the International Exchange Committee
(Department of Macromolecular Science)
Assoc. Prof. Tomoyuki Furuya, Member of the International Exchange Committee
(Department of Biological Sciences)
Assoc. Prof. Hirokazu Odaka, Member of the International Exchange Committee
(Department of Earth and Space Science)
Dr. Yuri Kamon(Lecturer), Member of the International Exchange Committee
(Center for International Affairs, Office of Research Administration)
Assoc. Prof. Luca Baiotti , International College

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