Podcast: Women of the periodic table, and harvesting energy from Wi-Fi

Host: Benjamin Thompson

Welcome back to the Nature Podcast. This week, we’ll be finding out how Wi-Fi signals could be harnessed to power electronics.

Host: Noah Baker

And celebrating some of the women behind the periodic table. I’m Noah Baker.

Host: Benjamin Thompson

And I’m Benjamin Thompson.

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Interviewer: Noah Baker

Wireless charging is all the rage right now. No wires – just power from the air. Chargers like this work by converting electricity into radiofrequency waves, also called RF waves. They travel through the air before being captured by a device and converted back into electricity – neat. Now, wireless chargers use very low frequency RF waves, and the devices being charged have to be very close to the source where it’s most powerful. But what if we could develop devices which could harness weaker RF signals from further away, and what if those signals were at a higher frequency, like maybe those used by Wi-Fi routers? Do I hear Wi-Fi charging? Well, as wireless tech develops, cities like London – where I’m sitting right now – are getting chock-full of high frequency radio waves and right now the energy is just wasted. That is what researcher Tomás Palacios from MIT in the US is trying to change. He’s developing a new type of energy-harvesting device which he hopes will future-proof our energy-gathering needs, and in Tomás’ mind, the future is big and the future is bendy. I gave him a call to find out more.

Interviewee: Tomás Palacios

The way I envision the future, we are going to have electronics everywhere. We are going to have electronics embedded in our clothes, on the floors in our buildings, in the bridges… basically everywhere. But then the question is how do we power those electronics, and I believe that an interesting approach is by harvesting whatever energy is out there. A relatively straightforward solution is to have sunlight, but the problem is that the sun is only out for that many hours a day, so then what is the next option? And it turns out to be RF signals coming from cell phones, Wi-Fi routers. That is energy that is already out there and we are not doing anything with it.

Interviewer: Noah Baker

And the technology that’s needed to harvest these sorts of signals is not a particularly new technology – it’s a device called a rectenna. Tell me, what is that and roughly how does it work?

Interviewee: Tomás Palacios

That is correct. The idea of the rectenna has been there for many decades and there are commercial devices that are working today based on this concept. The first thing you need to do is to have an antenna. That antenna takes the RF signals, and then the problem is that the RF signals are sinusoidal in nature and that means that they cannot be used to power electronics directly. So, to make them useful, you need to rectify them. So, you couple the antenna with a rectifying device and that combination is called a rectenna. The problem with that approach based on conventional electronics is that it’s relatively expensive and – what I think is more important – the form factor is very small.

Interviewer: Noah Baker

Yeah, and this form factor, the sort of shape of electronics, is very much at the heart of the work that you’re doing. Tell me, what’s wrong with the current form factor of the way that the electronics work at the moment and what needs to change?

Interviewee: Tomás Palacios

There is a mismatch between the electronics that we have today, which is very, very small – and there are lots of applications that really benefit from having small electronics – and the infrastructure that we are surrounded by. So, as we move in the direction of bringing sensors to everything we have, we need, I believe, to change the form factor of electronics. We need to move towards something that is a lot more flexible, mechanically flexible, to be able to embed in a wide variety of new objects, and also something that is compatible with the large dimensions of things around us.

Interviewer: Noah Baker

And your approach to create these new flexible, large-area electronics is to use 2D materials – these super-thin, maybe only a-couple-of-atoms-thick sheets of material that are popping up all over the place at the moment.

Interviewee: Tomás Palacios

Yeah, so the material we’ve used is called molybdenum disulfide, and it’s basically a three-atom-thick semiconductor that we grew by a process called chemical vapour deposition, which can actually be done on a roll-to-roll basis. So, that means that we can potentially produce thousands of square metres of this material with high enough quality to make these RF-harvesting devices.

Interviewer: Noah Baker

And so, you’ve created your device. Tell me some numbers. What is it able to do?

Interviewee: Tomás Palacios

For the first time in flexible electronics, we can harvest RF signals all the way till 10GHz, which basically covers 99% of the frequency bands of interest for Wi-Fi, cell phone-based stations, radio channels etc. And not only is it able to go to very high frequencies, but also, it’s able to harvest those signals in a fairly efficient manner. It’s actually enough to power some simple LED displays as well as some low-power electronic sensors and communication devices.

Interviewer: Noah Baker

How common is molybdenum? Is it something that you can feasibly use on a large scale? Would that be even cheap enough?

Interviewee: Tomás Palacios

I mean the big advantage is we don’t need that much of it. We only need three atomic layers. In volume it’s very, very small, so I do believe that the final cost of these RF-harvesting devices is going to be very low. But we are not selling these devices yet, I mean we haven’t really started the cost structure yet to know exactly what will be the final price, but they will be cheaper than conventional electronics, orders of magnitude cheaper.

Interviewer: Noah Baker

That was Tomás Palacios. You can read his paper over at nature.com/nature.

Interviewer: Benjamin Thompson

Listeners, 2019 is a big year for chemistry and for science. This year is the International Year of the Periodic Table of Chemical Elements, celebrating the 150th anniversary of Dmitri Mendeleev’s insightful mapping out of the elements way back in 1869. The periodic table’s wonder is in its simplicity, laying out elements according to their atomic number and properties. The table was made before many elements were discovered, or in some cases created, but Mendeleev’s system left gaps where they would fit. There were many scientists involved in filling in the table, by discovering elements, and learning more about them. But lots of these great scientists are underappreciated, or in some cases completely unrecognised, and is so often the way throughout science history, many of these unrecognised researchers were women. So, in Nature this week, we’ve a Comment article highlighting some of those women who were absolutely central to our understanding of the elements. You’ve certainly heard of double Nobel Laureate Marie Curie, but there are many other women who remain largely unknown. One of the Comment’s authors is Annette Lykknes from the Norwegian University of Science and Technology. I gave her a call and she told me about a female chemist who played an important role in piecing together the early periodic table.

Interviewee: Annette Lykknes

Just a few years after Mendeleev had presented his first periodic table, there was a Russian woman called Julia Lermontova, and she took up a challenge that was being discussed among the chemists at the time – how to order the platinum and metal elements in the right way because in order to place them in the periodic system in the right order, you need a very accurate atomic weight, as they called it at that time. In order to find that atomic weight, you needed to separate the elements, and this demanded very careful, chemical, analytical work. We don’t know exactly why she took up the work, whether it was because Mendeleev asked her, but at the very least we find her manuscript and correspondence between Mendeleev and her about it in his archives.

Interviewer: Benjamin Thompson

So, she was working to separate out the elements in the platinum-group so they could be correctly placed in the periodic table. Is she well remembered within the chemistry community?

Interviewee: Annette Lykknes

Not at all, she is mostly forgotten actually. Of course, she has been celebrated as one of the early chemists at that time, but she’s not celebrated for her work on the periodic table.

Interviewer: Benjamin Thompson

And scientists being forgotten is something that is mentioned several times in the piece you’ve written. Who else was really important at the time who doesn’t get the credit they deserve?

Interviewee: Annette Lykknes

When we’re talking about radioactivity, many women have been involved. Radioactivity was in fact a field that attracted many women, not just to Marie Curie’s laboratory, but also to the Laboratory of Radioactivity Research in Vienna and also elsewhere.

Interviewer: Benjamin Thompson

And why was that?

Interviewee: Annette Lykknes

One reason was that this was a new field, so it was not established as a male community, so to speak, with hierarchies between men. Also, the role of the supervisors – not just Marie Curie – was not actually particularly trying to recruit new women, but also the male leaders of the laboratories like Stefan Meyer in Vienna, Rutherford who was first in Canada and later in the UK, they have been characterised as very encouraging towards women.

Interviewer: Benjamin Thompson

At this time there were still a lot of gaps in the periodic table and chemists were working to fill them in, but sometimes there were more elements being discovered than there were gaps, so what was going on there?

Interviewee: Annette Lykknes

In 1913, Frederik Soddy, a British chemist, he proposed a new concept which he called isotopes, meaning the same elements could have different atomic weights. Actually, it was a woman called Margaret Todd, a physician, who coined the term when she was attending a dinner party with Soddy.

Interviewer: Benjamin Thompson

So how was the concept of isotopes proved?

Interviewee: Annette Lykknes

One way of proving it was to find one particular element that had different atomic weights. So, Soddy suggested, for example, that lead that was derived from uranium decay had a lower atomic weight than ordinary lead, or lead that came from decay of thorium would have a greater atomic weight. And this is where a woman comes in to the picture. So, this is a Polish-Jewish chemist called Stefanie Horovitz. She was working on radioactive uranium and radium ores, and so she separated out very pure samples of lead through careful extraction procedures and atomic weight determinations, and she was providing the first authoritative evidence for the concept of isotopes.

Interviewer: Benjamin Thompson

Well, let’s leap forward again then Annette to when researchers had a better idea of atomic structure. Who is one more female researcher who you think deserves better recognition?

Interviewee: Annette Lykknes

So, if we move a little bit further in time, into the 1920s, at that time many of the gaps in the periodic table had been filled already, but there were still a few that Mendeleev had predicted that had not yet been discovered. One of the women who were involved in this was called Ida Noddack. She was a German chemist. She met Walter who became her husband – he was a chemist too – and together they decided to take up the quest for finding the elements beneath manganese in the periodic table. And after some years they discovered the element they called rhenium, after the River Rhine.

Interviewer: Benjamin Thompson

As well as being a co-author on this week’s comment, you’ve also co-edited a forthcoming book about the women behind the periodic table. Again and again, many of these women were overlooked. Why did this keep happening?

Interviewee: Annette Lykknes

Quite often the women didn’t have prominent positions in their community. Quite often they were working with other men and they were part of teams and other people got the credit for it. So, when we look at women, it’s one way of unveiling the fuller picture of all the people working. Many of them were women, unpaid assistants, technicians, so we want to emphasise with this work that we want to bring the women to the fore, but also the many men who were not credited.

Interviewer: Benjamin Thompson

That was Annette Lykknes. You can read her Comment article which has stories about many more of the women behind the periodic table over at go.nature.com/periodictable, where you’ll find a host of other content celebrating the table’s 150th anniversary.

Host: Noah Baker

Stick around for the News Chat, where we’ve got the latest on the recently ended US government shutdown. But before then, Nick Howe, the newest member of the podcast team, is here with this week’s Research Highlights.

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Nick Howe

When your alarm clock alarm rings, do you groan and roll over or do you leap straight out of bed? Your response may be partly down to your genes. Scientists studied the genomes of nearly 700,000 people. They found 351 genetic regions associated with a person’s natural sleep rhythms, also known as their chronotype. The research suggests that wanting to sleep at a certain time may have much more of a genetic basis than previously thought. The authors also suggest associations between chronotype and health, with early birds having higher subjective well-being and a lower risk of depression. However, there’s still much to learn, as this latest study relies in part on self-reporting of sleep times, so more work needs to be done to confirm the role that these genetic regions play. Find that bedtime reading in Nature Communications.

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Nick Howe

Researchers from Spain have developed a virus that could help treat certain types of eye cancer in children. In a cancer of the developing retina, known as retinoblastoma, tumours overproduce a protein called E2F. The team behind this work designed a virus to kill retinoblastoma cells – this virus is unable to replicate without E2F, making it highly specific to the tumour cells. These targeted viruses could be especially useful when treating tumours

resistant to chemotherapy, negating the need to remove affected eyes. In the first small human trial of two patients, the virus successfully shrank small tumours in one of the participants. Have a look at this research in Science Translational Medicine.

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Interviewer: Benjamin Thompson

Finally then on this week’s show, it’s time for the News Chat and I’m joined here in the studio by Sara Reardon, reporter here at Nature. Hi, Sara.

Interviewee: Sara Reardon

Hello.

Interviewer: Benjamin Thompson

So, for our first story today then, Sara, let’s talk about the shutdown. This week, thousands of US federal employees are going back to work.

Interviewee: Sara Reardon

Yeah, the government has been shut down since before Christmas over funding disputes. They have agreed last week to reopen temporarily just for three weeks while they try and hash out some discussions. So at least for the time being, hundreds of thousands of employees are going to be going back to work.

Interviewer: Benjamin Thompson

Which has got to be good news if you’ve got bills to pay. This shutdown lasted for I think 35 days, which is a record in the US. What sort of an impact has this had on science?

Interviewee: Sara Reardon

It’s had an enormous impact. There have been many, many government scientists out of work, not sure how they’re going to be able to pay their bills, and now they have a lot of work to catch up on. I’ve seen some interviews with some government agencies like the FDA saying that it might take them a year to recover. They’ve just got all of these drugs that haven’t been being reviewed. There’s grant applications at the NSF that haven’t been being reviewed. Getting back into your email might be a hassle. It’s just going to take a really long time for them to be able to get back to normal, and then what’s possibly even worse is science that hasn’t been getting done over the last month here.

Interviewer: Benjamin Thompson

And do you have any examples of the sort of work that’s been affected?

Interviewee: Sara Reardon

There’s a very famous long-running ecological study on an island in the Great Lakes where there’s a wolf population. Researchers go out there every year to study how wolves are interacting with their prey, with moose, and they have to go at this time of year, and last I heard, they weren’t going to be able to go if it stretched out much beyond January. So, we’ll see if they’ll be able to go out there and see how the wolves are doing.

Interviewer: Benjamin Thompson

Thinking about the shutdown in the broader context, Sara, obviously, it is affecting directly folk in the US, but what about researchers around the world? Are they seeing any sort of ripple effects?

Interviewee: Sara Reardon

Well, researchers around the world rely on a lot of US datasets that NASA collect on climate. I’m sure there have been collaborations that have been affected – people haven’t been able to reach their US colleagues. Quite a few large scientific meetings had to go forward without the US contingent there. Nobody’s happy about this.

Interviewer: Benjamin Thompson

Right, so a lot of things have been affected then Sara, but as things stand, people are going back to work which has to be good news, right?

Interviewee: Sara Reardon

Yeah, it is good news. They are going to at least be able to start catching up on work, but everyone’s kind of living in this constant fear right now – is the impression I’ve had – of what’s going to happen in three weeks. They really want to get things back up and running if it’s only going to get shut down again very soon.

Interviewer: Benjamin Thompson

And so, this is a possibility then, so there’s a few weeks’ worth of funding and then do we know what happens afterwards?

Interviewee: Sara Reardon

We don’t. It could get shut down again; it may not. And I think that one of the things we have to talk about too is the long-term impacts of this and people’s willingness to want to work at government jobs. I live in Washington DC. I have friends who have been affected by the shutdown in the last three weeks and they’re thinking about getting new jobs now because this just could keep happening.

Interviewer: Benjamin Thompson

Well, let’s move on to our second story today, Sara, and it’s about drones. What’s the story here?

Interviewee: Sara Reardon

Yeah, so drones are being used in conservation. They’re used pretty frequently in a lot of different types of conservation work, monitoring animals, monitoring various ecosystems and in this particular case though, they’re being used in the Galapagos to drop poison on rats.

Interviewer: Benjamin Thompson

I guess rats aren’t good news for the Galapagos?

Interviewee: Sara Reardon

No, the rats eat eggs, they eat trees, they eat and otherwise destroy all of these species that are very special in the Galapagos. They’re just kind of bad news all round.

Interviewer: Benjamin Thompson

And why drones? I mean it seems like you could easily go out on foot and distribute this poison.

Interviewee: Sara Reardon

Well, you could, and that’s what people have been doing for a long time. They’ve been fighting against invasive rats for many, many decades, and had been making some progress until recently rats showed back up and instead of hacking their way through the forest to build trails to go out there, they realised they could just drop the poison from the air and distribute it that way. Drones are a lot cheaper and logistically easier to use than helicopters which is kind of historically what’s been done when you need to disperse something over an island, but yeah, this new technology is going to be the first test of whether you can do this on a large scale.

Interviewer: Benjamin Thompson

Well if this initiative has just started, how long do we need to wait to find out how effective it is?

Interviewee: Sara Reardon

Yeah, they just dropped the first round. They’re going to be doing another one in a couple of weeks here, and then they’re going to be monitoring the rats for the next two years. What I thought was kind of interesting about this story is that they had to only cover half of the island at first due to mechanical difficulties with the drones, and then they spread the rest of the poison on the island by hand. So that will actually enable scientists in the future to be able to compare those two halves and see whether the drones were more effective than humans.

Interviewer: Benjamin Thompson

Oh wow, so sort of an accidental experiment then?

Interviewee: Sara Reardon

Yeah.

Interviewer: Benjamin Thompson

Well, what are researchers themselves saying about this drone use?

Interviewee: Sara Reardon

Well, a lot of researchers in different parts of the world are interested in it. There’s some invasive possums in New Zealand, for instance, and people who want to eradicate them might want to use this in the future if it works out well. Though there is a little bit of cause to maybe not be concerned, but at least think about the fact that instead of going in and actually seeing that we are killing a lot of animals, it kind of lets you be detached from that reality, and I think that some conservationists want researchers to keep that in mind before they get too excited about never having to look at the rats that they’re killing, to just think that we are taking a lot of animal lives here and keep that in perspective.

Interviewer: Benjamin Thompson

Well, thank you Sara, and listeners, for more on those stories, head over to nature.com/news.

Host: Noah Baker

And that’s it for this week’s show. Don’t forget, you can get in touch with us on Twitter –

we’re @NaturePodcast –or on email at podcast@nature.com. I’m Noah Baker.

Host: Benjamin Thompson

And I’m Benjamin Thompson. Thanks for listening, see you next time.