Fuel-generating photosynthetic solar cell engineered for first time

A research team at the University of Illinois, Chicago, has developed a new form of solar cell that operates on the same basis as plant photosynthesis; cheaply and efficiently converting atmospheric carbon dioxide into usable hydrocarbon fuel, with the only energy it requires coming from sunlight.

While conventional solar cells require heavy batteries to store the electricity they produce from sunlight, the new solar cell directly converts carbon dioxide into fuel. These “artificial leaves”, if in operation on a large-scale solar farm, would be able to not only provide energy-dense fuel at an efficiency far beyond that of normal cells, but also remove significant amounts of carbon from the atmosphere in the process.

“The new solar cell is not photovoltaic – it’s photosynthetic,” said Amin Salehi-Khojin, assistant professor of mechanical and industrial engineering at UIC and senior author on the study.

“Instead of producing energy in an unsustainable one-way route from fossil fuels to greenhouse gas, we can now reverse the process and recycle atmospheric carbon into fuel using sunlight.”

Amin Salehi-Khojin (left) and postdoctoral researcher Mohammad Asadi pose with the artificial leaf

Amin Salehi-Khojin (left) and postdoctoral researcher Mohammad Asadi pose with the artificial leaf

The cell produces syngas, a mixture of hydrogen gas and carbon monoxide that can either be burned directly or converted into a range of hydrocarbon fuels, including diesel. Such a process is known as a reduction reaction, as it converts CO₂ into a burnable form of carbon.

Until now producing such reactions was inefficient, and relied on expensive precious metals as catalysts.

Deciding that they required a “new family of chemicals with extraordinary properties”, Salehi-Khojin and his team selected a group of nano-structured compounds called transition metal dichalcogenides (TMDCs) to focus on. These were placed in a two-compartment, three-electrode electrochemical cell along with an unconventional ionic liquid which functioned as an electrolyte.

The purpose of this was to determine the most efficient catalyst, and it worked: the team’s ultimate choice was nanoflake tungsten diselenide, a material which was found to be 1,000 times faster and 20 times cheaper than the previously used noble-metal catalysts.

However, there was still more to do to make the process work, as on its own, the catalyst can’t survive the necessary reaction to produce fuel. The solution was to add an ionic fluid with the catchy name ethyl-methyl-imidazolium tetrafluoroborate, mixed 50-50 with water, which allows the catalyst to endure the reaction.

“The combination of water and the ionic liquid makes a co-catalyst that preserves the catalyst’s active sites under the harsh reduction reaction conditions,” Salehi-Khojin said.

A lab demonstration of the technology producing syngas when exposed to artificial sunlight. Inline images courtesy of University of Illinois at Chicago / Jenny Fontaine

A lab demonstration of the technology producing syngas when exposed to artificial sunlight. Inline images courtesy of University of Illinois at Chicago / Jenny Fontaine

The technology, which has had a provisional patent application filed, should have a fairly high rate of adaptability, as it is usable on both large and small scales. Perhaps the most exciting possibility raised, however, is usage on Mars. Given that the planet’s atmosphere is mostly carbon dioxide, if water is found, these cells could go a long way towards contributing to possible settlement on the red planet.

Robert McCabe, National Science Foundation program director, said: “The results nicely meld experimental and computational studies to obtain new insight into the unique electronic properties of transition metal dichalcogenide.

“The research team has combined this mechanistic insight with some clever electrochemical engineering to make significant progress in one of the grand-challenge areas of catalysis as related to energy conversion and the environment.”

The dangers of space travel: Apollo astronauts experience increased cardiovascular problems

A new study has found that astronauts involved in the Apollo space programme experience higher rates of cardiovascular-related deaths than those who never ventured beyond low-Earth orbit – the cause of which is likely to be exposure to deep space radiation.

The paper, published in Scientific Reports by Florida State University (FSU) Dean of the College of Human Sciences Professor Michael Delp, notes that the men who travelled into deep space as part of the Apollo missions were exposed to very high levels of galactic cosmic radiation.

And it is this exposure to radiation that is now manifesting itself as cardiovascular problems, which could have deep implications for future missions beyond low-Earth orbit, including those to Mars.

Apollo 16 astronauts Thomas K Mattingly II and Charles M Duke undertake a spacewalk during the mission. Above: Duke in his role as lunar module pilot during the Apollo 16 lunar landing

Apollo 16 astronauts Thomas K Mattingly II and Charles M Duke undertake a spacewalk during the mission. Above: Duke in his role as lunar module pilot during the Apollo 16 lunar landing

The Apollo space programme ran from 1961 to 1972, with 11 manned flights into space – nine of which flew beyond Earth’s orbit into deep space. This study is the first to look at the mortality rate of these Apollo astronauts.

“We know very little about the effects of deep space radiation on human health, particularly on the cardiovascular system,” Delp explained. “This gives us the first glimpse into its adverse effects on humans.”

The research is of particular interest as the US, other nations and private organisations continue to make plans for deep space travel. Elon Musk ‘s SpaceX, for example, has proposed landing humans on Mars by 2026. And NASA plans to launch orbital missions around the moon from 2020 to 2030.

While astronauts have access to top medical care, the Apollo mission members did experience vastly different environmental conditions when they travelled into deep space – conditions that, the study has found, have affected their health.

The study revealed that 43% of deceased Apollo astronauts died from cardiovascular problems – four to five times higher than non-flight astronauts and those who travelled in low-Earth orbit.

Apollo 8 astronauts make their way to the launch pad to begin the mission, led by commander colonel Frank Borman and command module pilot James A Lovell Jr. Images courtesy of NASA

Apollo 8 astronauts make their way to the launch pad to begin the mission, led by commander colonel Frank Borman and command module pilot James A Lovell Jr. Images courtesy of NASA

A total of 24 men travelled into deep space as part of the Apollo lunar missions – eight have died; seven were included in the study (the eighth died after the data analysis had been completed).

Delp’s team carried out an animal test as part of the research, exposing mice to the type of radiation that Apollo astronauts would have experienced. After six months, or the equivalent of 20 human years, the mice showed damage to arteries that is known to lead to the development of atherosclerotic cardiovascular disease.

“What the mouse data show is that deep space radiation is harmful to vascular health,” Delp said. He is currently working with NASA to carry out further studies on the Apollo astronauts with regard to their cardiovascular health.

Researchers prove that microswimming robots that work together don’t have to stay together

Drexel University researchers have demonstrated how their microswimming robots can deliver medicine to targeted areas and perform surgery inside the body.

The “microswimmers” are essentially beads that come together in order to reach faster speeds when travelling through a liquid.

Once they’ve reached their target, the beads can separate and be individually controlled to deliver their medicinal payload or targeted treatments.

“We believe microswimmer robots could one day be used to carry out medical procedures and deliver more direct treatments to affected areas inside the body,” said U Kei Cheang, PhD, and postdoctoral research fellow in Drexel’s College of Engineering, U Kei Cheang.

“They can be highly effective for these jobs because they’re able to navigate in many different biological environments, such as the blood stream and the microenvironment inside a tumour.”

When linked, the microswimming robots move by spinning, and the more the robots spin the faster they move.

In a paper published in Nature Scientific Reports, the researchers documented how the longest chain that was examined by the group – 13-beads in length – was able to reach speeds of 17.85 microns per second.

This dynamic propulsion system is also the key to getting the robots to divide into shorter segments.

Once the robots reach a certain rate of rotation the chain separates and smaller beads remain that can move independently of each other.

Having separated, the robots can be manipulated and made to move in different directions if required.

“To disassemble the microswimmer we simply increased the rotation frequency,” Cheang said.

“For a seven-bead microswimmer, we showed that by upping the frequency 10-15 cycles the hydrodynamic stress on the swimmer physically deformed it by creating a twisting effect, which leads to disassembly into a three-bead and four-bead swimmer.”

Images courtesy of Drexel University

Images courtesy of Drexel University

Drexel University is partnering with ten institutions of research and medicine from around the world to develop this technology for performing minimally invasive surgery on blocked arteries.

But the work it has been doing on microswimmer robots represents the culmination of nearly a decade’s work into understanding the biomedical applications of microrobots.

“For applications of drug delivery and minimally invasive surgery, future work remains to demonstrate the different assembled configurations can achieve navigation through various in vivo environments, and can be constructed to accomplish different tasks during operative procedures,” the study’s authors write.

“But we believe that the mechanistic insight into the assembly process we discussed in this research will greatly aid future efforts at developing configurations capable of achieving these crucial abilities.”