A building material that lives and stores carbon

ETH Zurich

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Picoplanktonics shows large-format objects made of photosynthetic structures.

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Credit: (Image: Valentina Mori/ Biennale di Venezia)

The idea seems futuristic: At ETH Zurich, various disciplines are working together to combine conventional materials with bacteria, algae and fungi. The common goal: to create living materials that acquire useful properties thanks to the metabolism of microorganisms – "such as the ability to bind CO2 from the air by means of photosynthesis," says Mark Tibbitt, Professor of Macromolecular Engineering at ETH Zurich.

An interdisciplinary research team led by Tibbitt has now turned this vision into reality: it has stably incorporated photosynthetic bacteria – known as cyanobacteria – into a printable gel and developed a material that is alive, grows and actively removes carbon from the air. The researchers recently presented their "photosynthetic living material" in a study in the journal Nature Communications.

Key characteristic: Dual carbon sequestration

The material can be shaped using 3D printing and only requires sunlight and artificial seawater with readily available nutrients in addition to CO2 to grow. "As a building material, it could help to store CO2 directly in buildings in the future," says Tibbitt, who co-initiated the research into living materials at ETH Zurich.

The special thing about it: the living material absorbs much more CO2 than it binds through organic growth. "This is because the material can store carbon not only in biomass, but also in the form of minerals – a special property of these cyanobacteria," reveals Tibbitt.

Yifan Cui, one of the two lead authors of the study, explains: "Cyanobacteria are among the oldest life forms in the world. They are highly efficient at photosynthesis and can utilise even the weakest light to produce biomass from CO2 and water".

At the same time, the bacteria change their chemical environment outside the cell as a result of photosynthesis, so that solid carbonates (such as lime) precipitate. These minerals represent an additional carbon sink and – in contrast to biomass – store CO2 in a more stable form.

Cyanobacteria as master builders

"We utilise this ability specifically in our material," says Cui, who is a doctoral student in Tibbitt's research group. A practical side effect: the minerals are deposited inside the material and reinforce it mechanically. In this way, the cyanobacteria slowly harden the initially soft structures.

Laboratory tests showed that the material continuously binds CO₂ over a period of 400 days, most of it in mineral form – around 26 milligrams of CO2 per gram of material. This is significantly more than many biological approaches and comparable to the chemical mineralisation of recycled concrete (around 7 mg CO2 per gram).

Hydrogel as a habitat

The carrier material that harbours the living cells is a hydrogel – a gel made of cross-linked polymers with a high water content. Tibbitt's team selected the polymer network so that it can transport light, CO2, water and nutrients and allows the cells to spread evenly inside without leaving the material.

To ensure that the cyanobacteria live as long as possible and remain efficient, the researchers have also optimised the geometry of the structures using 3D printing processes to increase the surface area, increase light penetration and promote the flow of nutrients.

Co-first author Dalia Dranseike: "In this way, we created structures that enable light penetration and passively distribute nutrient fluid throughout the body by capillary forces." Thanks to this design, the encapsulated cyanobacteria lived productively for more than a year, the materials researcher in Tibbitt's team is pleased to report.

Infrastructure as a carbon sink

The researchers see their living material as a low-energy and environmentally friendly approach that can bind CO2 from the atmosphere and supplement existing chemical processes for carbon sequestration. "In the future, we want to investigate how the material can be used as a coating for building façades to bind CO2 throughout the entire life cycle of a building," Tibbitt looks ahead.

There is still a long way to go – but colleagues from the field of architecture have already taken up the concept and realised initial interpretations in an experimental way.

Two installations in Venice and Milan

Thanks to ETH doctoral student Andrea Shin Ling, basic research from the ETH laboratories has made it onto the big stage at the Architecture Biennale in Venice. "It was particularly challenging to scale up the production process from laboratory format to room dimensions," says the architect and bio-designer, who is also involved in this study.

Ling is doing her doctorate at ETH Professor Benjamin Dillenburger's Chair of Digital Building Technologies. In her dissertation, she developed a platform for biofabrication that can print living structures containing functional cyanobacteria on an architectural scale.

For the Picoplanktonics installation in the Canada Pavilion, the project team used the printed structures as living building blocks to construct two tree-trunk-like objects, the largest around three metres high. Thanks to the cyanobacteria, these can each bind up to 18 kg of CO2 per year – about as much as a 20-year-old pine tree in the temperate zone.

"The installation is an experiment – we have adapted the Canada Pavilion so that it provides enough light, humidity and warmth for the cyanobacteria to thrive and then we watch how they behave," says Ling. This is a commitment: The team monitors and maintains the installation on site – daily. Until 23 November.

At the 24th Triennale di Milano, Dafne's Skin is investigating the potential of living materials for future building envelopes. On a structure covered with wooden shingles, microorganisms form a deep green patina that changes the wood over time: A sign of decay becomes an active design element that binds CO2 and emphasises the aesthetics of microbial processes. Dafne's Skin is a collaboration between MAEID Studio and Dalia Dranseike. It is part of the exhibition "We the Bacteria: Notes Toward Biotic Architecture" and runs until 9 November.

The photosynthetic living material was created thanks to an interdisciplinary collaboration within the framework of ALIVE (Advanced Engineering with Living Materials). The ETH Zurich initiative promotes collaboration between researchers from different disciplines in order to develop new living materials for a wide range of applications.

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Journal

Nature Communications

DOI

10.1038/s41467-025-58761-y 

Method of Research

Computational simulation/modeling

Subject of Research

Not applicable

Article Title

Dual carbon sequestration with photosynthetic living materials

 

KAIST develops glare-free, heat-blocking 'smart window'... applicable to buildings and vehicles​

The Korea Advanced Institute of Science and Technology (KAIST)

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(From left) First author Hoy Jung Jo, Professor Hong Chul Moon

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Credit: KAIST Polymer Ionic Materials & Ionotronics Lab

In the building sector, which accounts for approximately 40% of global energy consumption, heat ingress through windows has been identified as a primary cause of wasted heating and cooling energy. Our research team has successfully developed a 'pedestrian-friendly smart window' technology capable of not only reducing heating and cooling energy in urban buildings but also resolving the persistent issue of 'light pollution' in urban living.

On the 17th of June, Professor Hong Chul Moon's research team at KAIST's Department of Chemical and Biomolecular Engineering announced the development of a 'smart window technology' that allows users to control the light and heat entering through windows according to their intent, and effectively neutralize glare from external sources.

Recently, 'active smart window' technology, which enables free adjustment of light and heat based on user operation, has garnered significant attention. Unlike conventional windows that passively react to changes in temperature or light, this is a next-generation window system that can be controlled in real-time via electrical signals.

The next-generation smart window technology developed by the research team, RECM (Reversible Electrodeposition and Electrochromic Mirror), is a smart window system based on a single-structured *electrochromic device that can actively control the transmittance of visible light and near-infrared (heat).

*Electrochromic device: A device whose optical properties change in response to an electrical signal.

In particular, by effectively suppressing the glare phenomenon caused by external reflected light—a problem previously identified in traditional metal *deposition smart windows—through the combined application of electrochromic materials, a 'pedestrian-friendly smart window' suitable for building facades has been realized.

*Deposition: A process involving the electrochemical reaction to coat metal ions, such as Ag+, onto an electrode surface in solid form.

The RECM system developed in this study operates in three modes depending on voltage control.

Mode I (Transparent Mode) is advantageous for allowing sunlight to enter the indoor space during winter, as it transmits both light and heat like ordinary glass.

In Mode II (Colored Mode), *Prussian Blue (PB) and **DHV+• chemical species are formed through a redox (oxidation-reduction) reaction, causing the window to turn a deep blue color. In this state, light is absorbed, and only a portion of the heat is transmitted, allowing for privacy while enabling appropriate indoor temperature control.

*Prussian Blue: An electrochromic material that transitions between colorless and blue upon electrical stimulation.

**DHV+•: A radical state colored molecule generated upon electrical stimulation.

Mode III (Colored and Deposition Mode) involves the reduction and deposition of silver (Ag+) ions on the electrode surface, reflecting both light and heat. Concurrently, the colored material absorbs the reflected light, effectively blocking glare for external pedestrians.

The research team validated the practical indoor temperature reduction effect of the RECM technology through experiments utilizing a miniature model house. When a conventional glass window was installed, the indoor temperature rose to 58.7°C within 45 minutes. Conversely, when RECM was operated in Mode III, the temperature reached 31.5°C, demonstrating a temperature reduction effect of approximately 27.2°C.

Furthermore, since each state transition is achievable solely by electrical signals, it is regarded as an active smart technology capable of instantaneous response according to season, time, and intended use.

Professor Hong Chul Moon of KAIST, the corresponding author of this study, stated, "This research goes beyond existing smart window technologies limited to visible light control, presenting a truly smart window platform that comprehensively considers not only active indoor thermal control but also the visual safety of pedestrians." He added, "Various applications are anticipated, from urban buildings to vehicles and trains."

The findings of this research were published on June 13, 2025, in Volume 10, Issue 6 of ACS Energy Letters. The listed authors for this publication are Hoy Jung Jo, Yeon Jae Jang, Hyeon-Don Kim, Kwang-Seop Kim, and Hong Chul Moon.

※ Paper Title: Glare-Free, Energy-Efficient Smart Windows: A Pedestrian-Friendly System with Dynamically Tunable Light and Heat Regulation

※ DOI: 10.1021/acsenergylett.5c00637

This research was supported by the Nano & Material Technology Development Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT and the internal research program of the Korea Institute of Machinery and Materials. 

  

igure 1. Operation mechanism of the RECM smart window. The RECM system can switch among three states—transparent, colored, and colored & deposition—via electrical stimulation. At -1.6 V, DHV•+ and Prussian Blue (PB) are formed, blocking visible light to provide privacy protection and heat blocking. At -2.0 V, silver (Ag) is deposited on the electrode surface, reflecting light and heat, while DHV•+ and Prussian Blue absorb reflected light, effectively suppressing external glare. Through this mechanism, it functions as an active smart window that simultaneously controls light, heat, and glare.

Figure 2. Analysis of glare suppression effect of conventional reflective smart windows and RECM. This figure presents the results comparing the glare phenomenon occurring during silver (Ag) deposition between conventional reflective smart windows and RECM Mode III. Conventional reflective devices resulted in strong reflected light on the desk surface due to their high reflectivity. In contrast, RECM Mode III, where the colored material absorbed reflected light, showed a 33% reduction in reflected light intensity, and no reflected light was observed from outside. This highlights the RECM system's distinctiveness and practicality as a 'pedestrian-friendly smart window' optimized for dense urban environments, extending beyond just heat blocking.

Figure 3. Temperature reduction performance verification in a miniature model house. The actual heat blocking effect was evaluated by applying RECM devices to a model building. Under identical conditions, the indoor temperature with ordinary glass rose to 58.7°C, whereas with RECM in Mode III, it reached 31.5°C, demonstrating a maximum temperature reduction effect of 27.2°C. The indoor temperature difference was also visually confirmed through thermal images, which proves the potential for indoor temperature control in urban buildings.

Credit

Authors: Hoy Jung Jo et al.

Journal

ACS Energy Letters

DOI

10.1021/acsenergylett.5c00637 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Glare-Free, Energy-Efficient Smart Windows: A Pedestrian-Friendly System with Dynamically Tunable Light and Heat Regulation

Article Publication Date

13-Jun-2025

 

Event-triggered adaptive neural network asymptotic tracking control of intelligent vehicles with composite learning

ELSP

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The ETC-ACC control scheme addresses the practical issues of excessive communication traffic and low tracking accuracy by integrating composite learning, event-triggered technology, and asymptotic convergence control methods.

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Credit: Yingjie Deng/Yanshan University，Fangcheng Liu/ Yanshan University，Songtao Wang/ Yanshan University, Yifei Xu/ Yanshan University, Tao Ni/ Yanshan University, Dingxuan Zhao/ Yanshan University

Researchers have developed an Event-triggered asymptotic composite neural tracking control scheme for intelligent vehicles, integrating radial basis function neural networks and a serial-parallel estimation model to compensate for system nonlinearities and uncertainties. Published in Advanced Equipment, this breakthrough has the potential to improve tracking precision of intelligent vehicles by ensuring asymptotic convergence of position error, enhance communication efficiency through event-triggered control, and boost system robustness against nonlinear dynamics and uncertainties, as validated by numerical simulations showing superior performance over traditional adaptive control methods.

High-precision tracking control for intelligent vehicles holds significant promise in advancing autonomous driving technology, yet it is challenged by system nonlinearities, uncertainties, and communication constraints that often lead to excessive traffic and low accuracy. Addressing this challenge, Professor Yingjie Deng from Yanshan University and Master's candidate Fangcheng Liu, in collaboration with researchers from the same institution, have developed an event-triggered asymptotic composite neural tracking control scheme that enhances both tracking precision and communication efficiency in intelligent vehicle systems. By integrating radial basis function neural networks, a serial-parallel estimation model, and integral-bounded functions, the scheme ensures asymptotic convergence of tracking errors while reducing communication traffic through variable threshold-based triggering conditions, with numerical simulations validating its superior performance in circular and abrupt trajectory scenarios.

“This control scheme marks a critical advancement in intelligent vehicle tracking," explains Professor Deng. "With reduction in communication traffic and a robust asymptotic convergence mechanism, this framework safely achieves high-precision tracking without compromising control efficiency, even in complex nonlinear driving scenarios."

"The newly developed control scheme delivers event-triggered updates, which are more communication-efficient than traditional continuous control methods. Its adaptive asymptotic convergence mechanism ensures compatibility with nonlinear vehicle dynamics, which are common in autonomous driving scenarios. Liu emphasizes, 'The event-triggered strategy significantly boosts communication efficiency and tracking accuracy, overcoming the challenges posed by system uncertainties and high-dimensional state spaces.'"

A major challenge in intelligent vehicle tracking is communication overload, which can lead to control delay and tracking deviation. The team addressed this by integrating a variable-threshold event-triggered mechanism and a serial-parallel estimation model into the control framework, reducing unnecessary communication updates during complex trajectory tracking.

While the team acknowledges the need for further research in addressing external disturbances and multi-vehicle coordination, this study represents a critical step toward more efficient and robust intelligent vehicle tracking control.

This paper ”Event-triggered adaptive neural network asymptotic tracking control of intelligent vehicles with composite learning” was published in Advanced Equipment. 

Deng Y, Liu F, Wang S, Xu Y, Ni T, et al. Event-triggered adaptive neural network asymptotic tracking control of intelligent vehicles with composite learning. Adv. Equip. 2025(1):0002, https://doi.org/10.55092/ae20250002.

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DOI

10.55092/ae20250002 

Method of Research

Computational simulation/modeling

Subject of Research

Not applicable

Article Title

Event-triggered adaptive neural network asymptotic tracking control of intelligent vehicles with composite learning

Article Publication Date

11-Jun-2025

 

Colorado River water market could help fish and farmers alike

A new water market model for the Colorado River basin could improve water security and restore ecosystems amid intensifying shortages.

Stanford University

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A market-based approach to managing water in the Colorado River basin could provide more reliable supplies for farmers, communities, and industry amid ongoing drought and excess demand. The right market design and a little extra investment could also help threatened fish species, researchers have found.

The study, published June 20 in Nature Sustainability, details a new system for leasing rights to water from the basin while reallocating some water to imperiled habitats. 

Not enough river water to go around

When the seven states of the Colorado River basin first divided water rights in the 1920s, they allocated more than the river could reliably deliver, especially during periods of drought. Today, the basin supplies drinking water to 40 million people and irrigation to 5 million acres of farmland across the southwestern United States, 30 tribal nations, and parts of Mexico. 

Climate change has exacerbated shortages, with studies indicating that recent Colorado River flows are near their lowest in at least 2,000 years. “The Colorado River is a marvel in terms of the scale of its impact on ecosystems, agriculture, economies, and people across the western U.S. and Mexico,” said Stanford Doerr School of Sustainability hydrologist Steven Gorelick, a senior author of the new study. “Given the overallocation of the river water, we explored how the needs of people and the environment can both be served.” 

Two decades into a historic megadrought in the U.S. West, the immediate need for effective solutions has grown. Out of 49 fish species native to the Colorado River basin, 44 are already threatened, endangered, or extinct. Standing agreements governing Colorado River management among states and between the U.S. and Mexico are set to expire after 2026.

“By strategically directing river water to the right places, even under drought conditions, fish can be saved with targeted restoration at nominal additional cost,” Gorelick said.

Congress allocated more than $4 billion in federal funds under the Inflation Reduction Act of 2022 for drought mitigation, largely through water market transactions that pay farms, cities, and industries in the region to use less water. “Those projects are not sufficient in many cases to meaningfully improve flow conditions for fish and ecosystems,” said the study’s lead author, water policy expert Philip Womble, who worked on the research as a graduate student and postdoctoral fellow at Stanford and is now an assistant professor at University of Washington. 

Voluntary water markets

Under the 1922 Colorado River Compact, states in the river’s Upper Basin agreed that they would not cause the river’s flow toward the Lower Basin – just below the nation’s second largest reservoir, Lake Powell – to be depleted below a 10-year rolling average of 7.5 million acre feet per year. 

Legal debates persist around whether the Upper Basin must deliver that amount of water amid climate-driven supply declines, and the possibility of U.S. Supreme Court litigation looms. “Under the interpretation that there’s a delivery obligation, the Upper Basin states basically bear the risk of climate change and climate change-driven reductions in water,” Womble explained. 

In an effort to avoid the risk of sudden cutbacks, water users in the Lower Basin states have created systems for voluntary water market transactions. Upper Basin states including Colorado, New Mexico, Utah, and Wyoming, meanwhile, have explored a water market designed to reduce water consumption and keep water flowing to Lake Powell. But existing programs generally do not prioritize water for critical fish habitats.

Womble, Gorelick, and colleagues including Stanford’s Barton “Buzz” Thompson wanted to quantify the extra cost associated with strategically improving fish habitat. 

The team developed a model to simulate transactions and ecological impacts in Colorado’s headwaters, which contribute nearly a quarter of the river’s natural average annual flow into Lake Powell. 

In the proposed market model, water sellers – including farmers, irrigation organizations, and cities – would lease senior water rights to governments and nongovernmental environmental organizations to protect threatened fish habitat. Those senior water rights are critical for environmental protection because they are fully allocated before newer, junior water rights receive any water.

“One key characteristic of water law across the western U.S. is our ‘use it or lose it’ principle,” Womble explained. “That can be a disincentive to water conservation.”

Modeling future drought scenarios

The team evaluated six scenarios to understand potential outcomes in a future drought year. They compared a “protected” market – where newer water users are legally barred from diverting restored flows – to an unprotected market with no legal flow protections.

Simulations showed that without reductions in water consumption, fish populations could face dire conditions for at least one month of the irrigation season along nearly the full length of the river. In contrast, strategic water transactions that reduce water use would benefit more than 380 miles of restorable river reaches. Hundreds of the most ecologically significant miles could see at least partial restoration of fish habitats.

“Instead of only reducing water consumption, strategic environmental water transactions would simultaneously reduce water consumption and preserve fish habitat at the lowest cost to the buyer,” the authors write.

Additional modeling results suggest that moderate cuts to water use could be achieved with $29 million spent in a protected market. Aggressive reductions might cost approximately $120 million. Comparable reductions would cost about 12% more in an unprotected market.

One possible source of the nominal extra funding to strategically benefit fish, Womble said, could be the growing number of technology companies and other corporations seeking to offset water use from their operations, including data centers.

“Spending a little bit more money, especially in headwaters, could have outsized ecological impact,” Womble said. The model indicates that the most stringent market design – with aggressive water-use reductions and legal protections for conserved water – is 29% more cost effective than a less formal option. “Although unprotected markets may be well suited for localized environmental flow improvement,” the authors write, “our results suggest they impede effective large-scale programs to substantially reduce water consumption.”

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Womble, JD ’16, PhD ’20, began work on the research as a graduate student at Stanford, where he earned degrees from the Emmett Interdisciplinary Program in Environment and Resources (E-IPER) and Stanford Law School. He is now an assistant professor in the Evans School of Public Policy & Governance at the University of Washington.

Gorelick is the Cyrus Fisher Tolman Professor in the Doerr School of Sustainability’s Department of Earth System Science. Thompson is the Robert E. Paradise Professor of Natural Resources Law in the Stanford Law School and Professor of Environmental Social Sciences in the Doerr School of Sustainability. Gorelick and Thompson are also senior fellows in the Stanford Woods Institute for the Environment. Gorelick directs the Global Freshwater Initiative, and Thompson is faculty director of the Water in the West program.

Co-author J. Sebastian Hernandez-Suarez was a postdoctoral scholar in the Stanford Doerr School of Sustainability’s Department of Earth System Science in Gorelick’s Water Resources and Hydrogeology program.

This research was supported by the Stanford Woods Institute for the Environment, Walton Family Foundation, the Stanford Doerr School of Sustainability’s Emmett Interdisciplinary Program in Environment and Resources (E-IPER), a Stanford Interdisciplinary Graduate Fellowship, Ishiyama Family Foundation, Babbitt Center for Land and Water Policy, Robert and Patricia Switzer Foundation, a Landreth Family Grant, and a McGee/Levorsen grant from the Stanford School of Earth, Energy & Environmental Sciences.

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Journal

Nature Sustainability

DOI

10.1038/s41893-025-01585-x 

Article Title

A strategic environmental water rights market for Colorado River reallocation

Article Publication Date

20-Jun-2025

 

Shifting from quantity to quality in climate adaptation finance to create real impact

Climate adaptation finance: From paper commitments to climate risk reduction

Delft University of Technology

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The quantity of adaptation finance has been a controversial political issue, and a critical negotiating point for develop­ing countries in international climate negotiations. At the United Nations climate conference (COP29) in Baku last year, developed countries agreed to provide more money for climate adaptation in emerging market and developing econo­mies. ‘But it is not only the amount of money that counts. At present, we have no evidence whether the existing finance distributed has been effective, and what we are actually trying to achieve with this finance in terms of climate risk reduction,’ says Verschuur.

Capacity building
‘Despite good intentions and skilled people dedicated to adaptation, the lack of impact is in part due to the wrong incentives being in place’. There is strong tendency now to focus on increasing adaptation finance commitments by adding adaptation components to existing and planned development projects. At the same time, we have considerably less focus on programmes that help build capacity, making necessarily policy changes, and put countries in charge of their own adaptation plans. But without the latter, adaptation will simply not be impactful.

Measures to reduce CO₂ emissions are often universally applicable. Climate adaptation measures, on the other hand, are heavily influenced by regional circumstances, such as agricultural needs, the local economy, and regional stakeholders. For climate adaptation to be truly effective, initiatives should originate from the countries themselves. Looking at climate adaptation in the Netherlands: the Dutch Delta Works are more than just dikes — they are the product of a deeply rooted policy culture. We should create such culture to emerging countries that face climate risks.

Urgent shift is necessary
Verschuur: ‘We provide five recommendations to improve adaptation programs and projects throughout the design cycle with adaptation finance, and the role of science to facilitate this.  These recommendations range from improving risk identification to planning, monitoring and creating an enabling environment for finance to be impactful.

Eventually, all five recommendations rely upon much strengthened capacity building efforts within governments, economic sectors, and communities. Verschuur: ‘Instead of the piecemeal capacity building efforts currently done, we urgently call for large-scale, coherent, efforts to enhance capacity. The next COP in Belem this October could be a good starting point for this discussion.’

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Journal

Science

DOI

10.1126/science.adx1950 

Method of Research

Literature review

Subject of Research

Not applicable

Article Title

Climate adaptation finance: From paper commitments to climate risk reduction

Article Publication Date

19-Jun-2025