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Empa Quarterly
RESEARCH & INNOVATION II #70 II JANUARY 2021
FOCUS
CLEAN
NEW CAR WORLD
CARS ARE LEARNING TO SEE
HOUSES HOARDING ELECTRICITY
ROBOTS KNITTING ROADS
www.empaquarterly.ch
[ EDITORIAL ]
[ CONTENT ]
[ FOCUS: CLEAN NEW CAR WORLD ]
IN PRAISE OF
CONTRADICTION
[ FOCUS ] [TOPICS ] [ SECTIONS ] Dear Readers,
17 AUTONOMOUS 08 BIOTECHNOLOGY 04 INSIGHTS Wherever you look these
DRIVING Melanin: Miracle drug days, one conjecture comes
Eye test for robot cars for wood protection 06 IN BRIEF to mind: we have forgotten
and more how to deal with contra-
20 CIVIL 34 ON THE ROAD diction. Instead of dealing
ENGINEERING 12 SUSTAINABILITY with counterarguments in a factual way, we
Road surface made of Renewable energy – are quick to play tough in controversial discus-
gravel and twine Game without limits? sions. This rarely pans out well; just look at the
furious Viking-shaman in the U.S. Capitol...
22 FUEL 15 MATERIALS
Synthetic methane from RESEARCH A glance at science might be useful here. Sci-
solar energy Modified wood can ence thrives on contradiction. The Austrian-Brit-
generate electricity ish philosopher Karl Popper considered it one, if
24 ELECTRIC DRIVE not THE high road to acquiring new knowledge.
Houses hoard solar power 28 HYGIENE Everything can be thought, said and asserted.
for cars Water filters against But every hypothesis, assertion or theory, as
germs soon as it has been put into the world, has to
20 be met with critical scrutiny. If it can be refuted,
30 THIRD WORLD it is thrown overboard and a new thesis is to be
Customized power grids developed – which in turn ... I think you get it.
for villages in Kenya
It is thus hardly surprising that sometimes,
when the state of knowledge is still patchy,
[ COVER ] [ IMPRINT ] different scientists favor different ideas. The
How well can
self-driving cars see? PUBLISHER Empa public often perceives this as “cacophony”
Empa‘s test vehicle
has a laser scanner on Überlandstrasse 129 and disunity within the research community.
board that produces
highres images like 8600 Dübendorf,Schweiz In fact, however, we merely see scientists at
this. Additionally the
system uses cameras www.empa.ch work and observe how they check their own
and radar scanners.
Empa wants to find out EDITORIAL Empa Kommunikation and other people’s ideas for disagreements.
how accurately these
sensors recognize the LAYOUT PAUL AND CAT.
17 22
world. Page 17.
www.paul-and-cat.com
CONTACT Phone. +41 58 765 47 33
We could take an example from this way of
working in future social and political de-
empaquarterly@empa.ch bates. However, this means we have to be
www.empaquarterly.ch prepared to question our very own convic-
PUBLISHING SEQUENCE tions, not just those of our counterparts.
quarterly
PRODUCTION Enjoy reading!
Printed Matter
Photos: iStockphoto, Empa
rainer.klose@empa.ch
myclimate.org/01-21-462265
Your MICHAEL HAGMANN
ISSN 2297-7414
Empa Quarterly (English edition)
28 30
2 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 3
[ INSIGHTS ]
SHIMMERING PROTECTION
The varnish influences vibration, stability and mois-
ture content of a violin. Empa researchers, together
with PSI scientists, have now been able to use the
latest imaging techniques such as in-situ neutron
tomography to gain insights into the depths of
varnished violin wood. Under the UV light micro-
scope it is possible to see how the varnish covers
the honeycomb-like wood structure. Depending on
the type of varnish it also penetrates the wood to
varying depths. This picture shows a shellac-alcohol
varnish / oil varnish in orange / blue.
Further information on the topic is available at:
https://www.nature.com/articles/s41598-019-54991-5
Sarah Lämmlein/Scientific Reports
4 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 5
[ IN BRIEF ]
STEP2 – NEW UNIT AT NEST GLUE FOR WOUNDS
START-UP
Sebastian Loy
and Tino Matter
(right) developed
The first prize of the 2020 «Empa Innovation Award» the new tissue
went to a novel tissue adhesive technology that adhesive and
founded the
promises faster and safer wound healing. It was
startup company
INNOVATIVE developed by researchers from Empa‘s «Particles-Bio- Anavo.
The two-story STEP2 unit will
logy Interactions» lab together with ETH Zurich‘s
be built on the top platform of
the NEST building. Nanoparticle Systems Engineering Lab. Unlike
previous wound adhesives, which consist mainly
of the body‘s own protein fibrin, the technology is
based on a combination of inorganic nanoparticles.
The adhesive particles bind particularly well to bone
or soft tissue. Accelerated coagulation improves
the treatment of external and internal wounds.
www.empa.ch/web/s604/empa-innovation-award-2020
A spiral staircase in the shape of a spine from 3D printing, a ribbed filigree ceiling that requires around a third less material,
and an energy-efficient building envelope that ensures optimum comfort: a new Unit is being planned at NEST. STEP2 – as it is
called – brings together innovations in the fields of circular economy, industrial and digital fabrication, and building envelope
and energy systems. The two-story unit will be built on the top NEST platform and is scheduled for completion in summer 2022.
www.empa.ch/web/nest/step2
DURABLE
The concrete beam
DATA CURRENT reinforced with a
The new 5G mobile communi- steel lamina has
cations standard makes data been supporting a
transmission much more efficient. HOW DOES 5G load of just over six
tons since 1970.
AFFECT THE CLIMATE?
Researchers at Empa and the University of Zurich have
been mandated by the swisscleantech trade association
and Swisscom to study the impact that the 5G mobile
Photos: James Yarema für Unsplash, ROK Architekten
communications standard will have on greenhouse
gas emissions. The study shows that the expansion of
BY HOOK OR BY CROOK
the 5G network can significantly reduce environ- Since 1970, Empa has been running a globally unique test to investigate the long-term behavior of bonded steel
mental impacts. One reason for this is greater reinforcements on a concrete beam. Investigations like this have contributed to the fact that bonded reinforcement is
energy efficiency. Added to this are savings due now state of the art as a strengthening method, and engineers have confidence in this construction method.
Photos: Empa, anavo
to intelligent power grids or more targeted use
www.empa.ch/web/s604/biegekriechversuch
of fertilizers and pesticides in agriculture.
www.empa.ch/web/s604/5g-netz
6 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 7
[ BIOTECHNOLOGY ]
THE "BLACK GOLD"OF I
ts properties are astonishing and its as a pigment, but also far beyond for
applications manifold: the pigment the development of innovative com- A PIGMENT AGAINST
melanin, which, for instance, pro- posite materials,” says Empa research- ENVIRONMENTAL STRESS
MUSHROOMS
tects human skin from harmful UV er Francis Schwarze from Empa‘s "Melanin" is a generic term for a large
light (and gives us a summer tan), is a “Cellulose & Wood Materials” lab. group of pigments. The pigment melanin
veritable treasure trove for new materials gives our hair, eyes and skin its color. It is
and technologies. Although the miracle In their quest for simpler, cheaper pro- found in bird feathers, sheep wool and in
substance occurs naturally, the com- cesses for the production of natural mel- the ink of squids. Plants, fungi and even
plex biopolymer can only be produced anin in large quantities, Schwarze and bacteria also produce the miracle substance.
artificially at an industrial scale through his team came across a fungus, which is Its task: to protect the organism from
Empa researchers have succeeded in extracting the pigment melanin in large quantities from expensive and complex processes, actually a common saprophytic fungus environmental stress. The darkening of the
a fungus. The gigantic Armillaria fungus in the service of science is one of the largest and during which some of the compound‘s that grows in the forest: Armillaria cepis- skin when exposed to the sun is but one
oldest living organisms in the world. Potential applications for the “black gold” range from properties are lost. To date processes for tipes. Its amazing metabolism enables example. Fungi, on the other hand, have
wood preservatives to the construction of water filters and historic musical instruments. extracting natural melanin from microor- the fungus to bind heavy metals, make an even more amazing ability: thanks to
ganisms only have low yields. wood glow in the dark – and produce melanin, they can even use radioactivity to
Text: Andrea Six melanin on a massive scale. “We have generate energy in their own metabolism.
selected a promising strain of A. cepis-
tipes, that allows us to produce around
1,000 times more melanin than with
other fungi” says Schwarze. The Anh Tran-Ly. Using electrospinning, the
trick: A. cepistipes is cultivated polymer mixture was spun into ultra-fine
in a nutrient fluid, and, in fibers to form membranes. The Empa
the presence of a precur- team found that these melanin-based
sor, tyrosine, the fungus composite membranescan remove up to
releases melanin into 94 percent of lead from polluted water.
the environment. “In
this way we have de- AS BLACK AS EBONY
veloped a sustainable In nature, fungi use melanin to protect
production method, themselves against other organisms
which no longer re- that compete for nutrients and space
quires time-consuming in the environment. With the new
extraction steps used in technology, the pigment can now
previous microbiological also be used to protect much larger
processes,” explains the communities from human influence:
Empa researcher. In three melanin can be used to conserve
months A. cepistipes produces tropical forests where highly priced
around 20 grams of melanin. and much sought after ebony grows.
The scalable and sustainable production Tropical ebony wood is particularly pre-
of melanin now enables Empa research- cious because of its unique dark color. A
ers to advance projects to develop inno- sustainable method that upgrades native
It is therefore not surprising that the vative materials for a range of industrial Norway spruce wood to a visually equal-
DESTRUCTIVE
Like a sponge, the watery porling grows substance is many times more expen- applications. These include, for example, ly attractive product allows vulnerable
on wood surfaces and attacks its structure sive than gold. Empa researchers have a system for water purification: since tropical forests to breathe a sigh of relief.
even in the depth.
now developed a method to produce melanin is able to bind heavy metals, “When spruce wood is impregnated with
the “black gold” in a simple and highly it can be used to develop new types a melanin suspension, a deep dark wood
scalable process. “Melanin is extremely of water filters. “We have integrated can be produced that is comparable to
Photo: Empa
stable when exposed to environmental melanin into artificial polymers such as ebony,” says Empa researcher
influences and is interesting not only polyurethane,” explains Empa researcher Tine Kalac.
8 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 9
[ BIOTECHNOLOGY ]
To enable the black melanin to penetrate it covers the registers of the human Other woodwind instruments built today
the wood, the researchers used another voice and can thus “carry” a choir, the using domestic, less resistant woods
“helper” from their fungal trick box: passionate instrument maker explains. could also benefit from such an environ-
Physisporinus vitreus – the white rot fun- mentally friendly wood treatment. Thus,
gus – is also a saprophyte that colonizes Although today‘s trend towards histor- the collaboration with the Empa team is
wood, thereby enhancing wood perme ically informed performances means exciting in more ways than one. ■
ability. It grows sponge-like on trees that the Serpentino is in great demand,
and preferentially decomposes lignin Berger is unable to supply its customers
within wood. With the help of a method with instruments: the peculiarly curved
developed at Empa, the wood is now original instruments have become rare.
GREEN LIGHT first treated with the white rot fungus for Because the snake-shaped instrument AS BLACK AS EBONY
Top: The Armillaria six weeks to allow the melanin suspen- made of walnut wood not only creates Empa researcher Tine
fungus colonizes Kalac applies melanin
wood and makes it
sion to penetrate deeply into the wood, an incomparable sound – there is also as a varnish to Norway
glow brightly in the without altering the wood‘s stability. a war raging inside the “little snake”: spruce wood.
dark with its own condensation from the musicians‘
bioluminescence.
Center: Melanin is SERPENTINO – THE LITTLE SNAKE breath creates a humid microclimate
also found in squid AMONG INSTRUMENTS that provides excellent conditions for the
ink.
Bottom: An Armillaria Since Armillaria fungi use melanin as growth of all kinds of microorganisms.
fungus network is a weapon against competitors, it is Thus the conditions for bacteria and fun-
protected by melanin
only logical to use melanin to protect gi are favorable for the decomposition of
and can be several
square kilometers wood from fungi. In order to develop the centuries-old instruments gradually
in size. a melanin-based wood preservative, destroying the last original specimens.
Empa researchers are participating in
a recently launched interdisciplinary The research project‘s faithful serpen-
project supported by Innosuisse, the tino replicas are to be protected from
Swiss Innovation Agency. The goal is to this damage. This is where Empa‘s
reconstruct a historical wind instrument, melanin comes in: “If we can use a
the Serpentino (in English: small snake). melanin-based wood preservative, not
only the newly built serpentinos can be Further information on the topic is available at:
Together with the University of Applied protected against decay,” says Berger. www.empa.ch/web/s302
Sciences and Arts Northwestern Switzer-
land and the Basel Historical Museum,
the industrial partner in the project is
STEPHAN BERGER
the company SBerger Serpents in Le Bois A MOST GIGANTIC FUNGUS containing melanin, and colonize new habitats The Serpentino: a
(JU), which is responsible for the practi- The honey fungus is one of the most and food sources. These so-called rhizomorphs peculiar shape with a
SCHWARZ WIE
EBENHOLZ touching sound.
cal implementation of the research pro- amazing organisms on Earth. Inconspi- can also penetrate tree roots as parasites,
Empa-Forscher
Tine Kalac wertet ject. Company founder Stephan Berger is cuously, it lives and grows in forest soils ascend the trunk and decompose their host
gewöhnliches enthusiastic about the rebirth of this rare and colonizes wood debris and trees with from within. With a size of several square kilo-
Fichtenholz mit
instrument: “The Serpentino was used its rhizomorphs. The fruting body is mus- meters, the largest living organism in the world,
Melanin auf.
over 400 years ago and was the godfa- hroom-shaped with cap, stipe with ring an approximately 2400-year-old Armillaria net-
ther of modern instruments such as the around the stipe, like a bracelet, which gives work, is expanding in the US state of Oregon.
saxophone and the tuba,” he explains. the fungus its latin name «Armillaria». In Switzerland, the largest fungus in Europe is
Although it is a technical challenge for loacted at the Ofen Pass. This Armillaria covers
musicians to master the instrument, the Much more impressive, however, is his network an area of 50 soccer fields. It owes its age of
Photos: Empa, Xavier Voirol
sound is incomparable, enthuses Berger. of black strands, which grows over the wood around 1000 years to the pigment melanin,
Photos: Empa, unsprash
“The Serpentino creates sounds that are and in the soil. Mushroom threads join which protects the black fungal threads from
rich in overtones and deeply touching”. together to form thick bundles several meters environmental damage and competitors.
Originally, the wind instrument was used long, surrounded by a black protective layer
in churches to support singing because
10 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 11
[ SUSTAINABILITY ] [ SUSTAINABILITY ]
ECO-ENERGY WITHOUT LIMITS?
T
Even a sustainable he Earth has its limits. We are becoming more and more aware compensate for such disruptions to a certain extent. However, if they are
circular economy of this in view of the climate crisis, the increasing extinction of too large, the risk of exceeding so-called “tipping points” increases. This
doesn’t run without species and the littering of the oceans (and even space) as a result would result in rapid and irreversible changes in the Earth system, such as
energy. Solar panels of human activity. In response, governments and institutions the melting of the polar ice caps, which in turn would accelerate climate
and wind farms, the world over are championing the concept of a circular change. In order not to exceed these tipping points, the size of the
tidal and geothermal economy. By closing material cycles, the environmental impacts land area occupied must not exceed the planetary boundary.
power plants: they associated with the extraction of raw materials shall be Beyond the scale, the way in which the land is used is also
all divert energy avoided and the waste problem solved. This approach is, crucial: solar plants instead of forests, for example, disrupt
from energy fluxes however, not sufficient to build a sustainable society in biodiversity, evaporation and thus the water cycle, the
that had remained and by itself, as it leaves the questions open of how radiation of heat back to space, and much more.
untapped since time much and how quickly materials can be cycled and "Wind power,
immemorial. The what energy is used to power these cycles. After The same upper limits for land occupation not
hydropower and
question is therefore: all, in a truly sustainable society, not only mate- only applies for direct solar energy use but also
what part of these rial flows but also energy flows must remain to the harvesting of so-called chemical ener-
biomass pro-
energy fluxes can within the limits set by our home planet. gy - that is, to agriculture and forestry, which duction are also
mankind use for produce food and fodder, heating materials, powered by the
its own purposes ENERGY FOR “RUNNING” THE EARTH fuels, and building materials. The produc- sun – but there
without damaging A key question is thus: is there enough tion of technical energy competes with are losses in
the Earth’s energy renewable energy available globally to food production on many surface areas. the process.
system? Empa re- sustainably manage material flows without
It is better to
searchers have devel- violating planetary boundaries? This ques- ELECTRICITY AS "UNIVERSAL CURRENCY"
oped an approach harvest energy
tion is being investigated by a team led by In order to be able to compare or add up
to estimate this. Harald Desing from Empa’s Technology and the various potentials for renewable ener-
directly, with
Society lab. If we look at Earth as a system, gy, the Empa researchers have converted photovoltaics."
Text: Harald Desing it only exchanges energy with space. By far them into electrical energy equivalents. To
the largest part of the energy brought into the do this conversion, efficiencies of power
Earth system is solar radiation, supplemented plant technologies available today are used in
by minor contributions from planetary motion the calculations. It makes a difference whether
and geothermal energy. These energy fluxes had electricity is generated from solar energy, wood
always been used entirely by the Earth itself. They or hydropower. These conversion losses further
have powered its many subsystems, such as the oceans, reduce the possible harvest of some potentials sig-
atmosphere and forests, but also reflective ice surfaces. nificantly. The result of the study is surprising: 99.96 %
of the energy arriving on Earth from space is needed to
Most of these subsystems convert the incoming energy into fur- power the Earth system and food production, therefore only
ther renewable energy fluxes, for example wind and water currents 0.04 % can be used technically. Nevertheless, this potential is
or biomass production. In these conversions, free energy, called exergy, is still about ten times higher than today’s global energy demand.
extracted from the incoming energy fluxes. Regardless whether energy con-
versions are taking place in the natural Earth system or in the technosphere A further result is, on the other hand, hardly surprising when looking
created by humans, all the energy is ultimately radiated back into space. at conversion losses: we should prefer to harvest and use the avail
IT'S GETTING HOT
NASA uses this image to able energy through direct solar energy conversion. After all, almost
SOLAR PARKS MAY ALSO CHANGE THE CLIMATE – IT’S A MATTER OF SCALE illustrate global methane all renewable energy resources – including wind, hydro power and
Photo: Nasa
emissions. Methane is the
As humanity increasingly diverts renewable energy fluxes to its activities, second most important
biomass production – are ultimately powered by the sun. Direct use of
the parts available to the Earth system are reduced. The Earth system can greenhouse gas, after CO2. solar energy means fewer conversion steps and thus fewer losses.
12 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 13
[ SUSTAINABILITY ] [ MATERIALS RESEARCH ]
VOLTAGE FROM
PHOTOVOLTAICS ON ALL SEALED SURFACES today’s demand per capita in Switzer- factors include the availability of raw
Much of the sun’s energy could be land, desert areas would also have to be materials, but also financial and human
harvested from a small portion of the used. All other energy potentials (e.g. capital, environmental impacts during
Earth’s deserts, but this is technically from wind or biomass) are orders of raw material extraction or production,
THE PARQUET
and logistically challenging. The re- magnitude smaller than the direct use of operation and disposal of the plants, and
search team of the “Technology and solar energy – and some resources are the need for additional infrastructure
Society” Lab therefore considers solar already overused. Nevertheless, they can for energy distribution and storage.
energy harvested on desert areas as a play a significant role locally, especially
global energy reserve in case all other because they can reduce the need for Currently, the research team is exploring
harvesting possibilities are exhausted. storage capacity – a problem that has how such a pathway from a fossil to a
Researchers at Empa and FULL OF ENERGY
not been considered in the study. solar society might look like. The solar Modified wood can
As a consequence, we should start energy system must not only be large
ETH Zurich have made generate electricity
using already sealed surfaces world- DESERT REGIONS AS A RESERVE enough to meet global demand, but
wood flexible and turned through deformation.
Is a tango enough
wide, e.g. building roofs and facades, Simply building solar plants en masse must also be able to replace the fossil
it into a micro-generator. for dim light?
but also roads, railroads and parking and the energy problem is solved? It’s fuel system quickly enough to avert the
When it is loaded, electri-
lots. This area would be sufficient to not quite that simple, of course. In their climate catastrophe in time. ■
cal voltage is generated.
power a global 2000-watt society. study, the Empa team only looked at
In this way, the wood can
the first step – calculating the available
serve as a bio-sensor – or
However, if one would like to raise the energy potential. The actual amount of
generate usable energy.
Further information on the topic is available at:
global energy demand to the level of energy available will be smaller: limiting www.empa.ch/web/s506
Text: Stefanie Zeller
EMPA SHOWS THE WAY
Harvesting solar energy on all roofs
and facades is possible. The NEST unit
Solace does not have a roof. It only
harvests electricity and heat through
its turquoise façade.
I
ngo Burgert and his team have ty can be generated by some kind of use materials that are unsuitable for use
proven it time and again: wood is “wood sponge” using a simple chemi- in biomedical applications, such as lead
so much more than “just” a build- cal process. This is where the so-called zirconate titanate (PZT), which cannot
ing material. Their research aims at piezoelectric effect comes into play. be used on human skin due to the lead
extending the existing characteristics it contains. It also makes the ecological
of wood in such a way that it is suitable VOLTAGE DUE TO DEFORMATION disposal of PZT and Co rather tricky.
for completely new ranges of applica- Piezoelectricity means that an electric Being able to use the natural piezoelec-
Photo: Roman Keller, istockphoto
tion. For instance, they have already voltage is created by the elastic defor- tric effect of wood thus offers a number
developed high-strength, water-re- mation of solids. This phenomenon is of advantages. If thought further, the
pellent and magnetizable wood. In a mainly exploited by metrology, which effect could also be used for sustain
recent study, his team, collaborating uses sensors that generate a charge able energy production. But first of all,
with the research group led by Francis signal, say, when a mechanical load is wood must be given the appropriate
Schwarze, has shown how electrici- applied. However, such sensors often properties. Without special treatment,
14 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 15
[ MATERIALS RESEARCH ] [ FOCUS: CLEAN NEW CAR WORLD ]
wood is not flexible enough; when layers. “We take advantage of the hierar- It would therefore be conceivable to de-
subjected to mechanical stress; there- chical structure of wood without first velop a wooden floor that is capable of
fore, only a very low electrical voltage is dissolving it, as is the case in paper pro- converting the energy of people walking
generated in the deformation process. duction, for example, and then having to on it into electricity. The researchers also
reconnect the fibers”, says Burgert. The tested the suitability as a pressure sensor
FROM BLOCK TO SPONGE resulting white wood sponge consists on human skin and showed that it could
Jianguo Sun, a PhD student in Burgert‘s of superimposed thin layers of cellulose be used in biomedical applications.
team, used a chemical process that is the that can easily be squeezed together
basis for various “refinements” of wood and then expand back into their original However, there is still a long way to
the team has undertaken in recent years: form – wood has become elastic. go before the “piezo” wood can be
delignification. Wood cell walls consist of used as a sensor or even as an elec-
three basic materials: lignin, hemicellu- ELECTRICITY FROM WOODEN FLOORS tricity-generating wooden floor. But
loses and cellulose. “Lignin is what a tree Burgert‘s team subjected the test cube the advantages of such a simple yet
needs primarily in order to grow to great with a side length of about 1.5cm to renewable and biodegradable piezoelec-
heights. This would not be possible with- about 600 load cycles. The material tric system are obvious – and are now
out lignin as a stabilizing substance that showed an amazing stability. At each being investigated by Burgert and his
connects the cells and prevents the rigid compression, the researchers measured colleagues in follow-up projects. ■ TEST DRIVE
The radar- and
cellulose fibrils from buckling,” explains a voltage of around 0.63V – enough
laser-equipped
Burgert. In order to transform wood into for an application as a sensor. In further Lexus does its
a material that can easily be deformed, experiments, the team tried to scale laps on the
Empa campus.
lignin must at least partially be “extract- up their wooden nanogenerators. For Dejan Milojevic
ed”. This is achieved by placing wood in example, they were able to show that (left) and
Miriam Elser
a mixture of hydrogen peroxide and ace- 30 such wooden blocks, when loaded
designed the
tic acid. The lignin is dissolved in this acid in parallel with the body weight of an driving tests.
Further information on the topic is available at:
bath, leaving a framework of cellulose adult, can light up a simple LCD display. www.empa.ch/web/s302
VISION TEST FOR
NANOGENERATOR
After the rigid wood
structure (top) has
been dissolved with
AUTONOMOUS CARS
an acid, flexible cel-
lulose layers remain Cars that autonomously navigate from A to B are expected to be a common sight in a few years from now.
(bottom). When
pressed together, But road approval is still a long way off. One important aspect: how can we tell a self-driving car has become
differently charged “blind” with age, i.e., its sensors would need to be replaced? An Empa team is looking for a solution.
areas are displaced
against each other.
The surface of the Text: Rainer Klose
material becomes
electrically charged.
Photos: Empa
Photo: Empa
16 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 17
[ FOCUS: CLEAN NEW CAR WORLD ] [ AUTONOMOUS DRIVING ]
T
he five meter-long Lexus RX- strictly obeys speed limits and autono- happens in a black box. The know-how suisse, FEDRO and industry partners.
450h leads a rather contem- mously maneuvers around parked cars. is worth a lot of money and is carefully TECHNICAL PROFILE OF LEXUS RX-450H TEST VEHICLE While Empa is investigating commer-
plative life at Empa. It never kept by Google, Apple, Tesla, Cruise cially available sensors in practical use,
• Hybrid powertrain
takes long trips. Instead, the TRUST IS GOOD, CONTROL IS BETTER LLC and the other major manufacturers the Swiss Federal Institute of Metrology
SUV dutifully does its laps If the Californians have already come developing autonomous vehicles. They • 3.5-liter V6 gasoline engine 183 kW/249 hp (METAS) is analyzing the same sensors
on a special track just 180 meters long this far, what sense does it make to drive don’t let anyone look into their cards • Two electric motors with 123 kW and 50 kW in a laboratory environment. The next
in a secluded backyard of the Empa around in a backyard in Dübendorf? generation of vehicle sensors is also
• Acceleration (0–100 km/h): 7.8 s
campus. The scenery is not particularly Miriam Elser explains why. She works in THE NEEDLE IN THE DATA HAYSTACK already the subject of research. This part
spectacular: the Mobileye camera be- Empa’s Automotive Powertrain Technol- Sensor quality plays an important role • Top speed: 200 km/h of the project is being undertaken by
hind the windshield sees freshly painted ogies lab and is leading the project with in the eventual approval of autono- the Institute for Dynamic Systems and
• Conversion kit to self-driving vehicle from autonomoustuff.com
lane markings on aging concrete; the the Lexus. Empa is breaking new ground mous cars for public transportation. The Control Engineering at ETH Zurich.
Gas pedal, brake, steering, transmission, horn, turn signals and driving lights
Velodyne lidar scans the window front with this project: previously, she and her operational safety of such vehicles falls can be switched remotely
of always the same lab building at every colleagues had been working on power- within the remit of the Swiss Federal AVOIDING ACCIDENTS
turn, and the Delphi radar behind the trains, renewable fuels and exhaust gas Roads Office (FEDRO), which is provid- • Self-driving vehicle starter kit from autonomoustuff.com There is not much time left to devel-
Lexus’ radiator grille routinely meas- purification, as well as vehicle operation. ing financial support for the research at • "AStuff Nebula" driving computer, Velodyne lidar, Mobileye camera, op the scientific basis for evaluating
ures the distance to five tin trash cans Now, for the first time, the Empa team Empa. FEDRO wants to be able to assess Delphi Aptiv ESR radar and Robot Operating System (ROS) and assessing autonomous cars.
set up to either side of the course. is also looking at self-driving cars. the functionality of autonomous systems The competition around self-driving
at regular intervals – and independently cars is enormous, and the automo-
AT THE SAME TIME, IN CALIFORNIA ... “We are investigating how these sensors of the manufacturers. The authority’s tive industry could soon be equip-
Thousands of miles to the west, on the work in different environmental condi- experts also want to make it possible ping its vehicles for this purpose.
U.S. Pacific coast, things look a bit more tions, what data they collect and when to conduct a kind of “witness inter-
dramatic. “Wow, I didn’t think the car they make mistakes or even fail,” says view” if an autonomous car has been Whether self-driving cars will in future
could do that,” says Sam Altman. He’s the researcher. “Every human driver has involved in an accident. The problem be able to avoid accidents and traffic
the head of OpenAI, an artificial intelli- is that each second the sensors collect is the subject of ongoing research.
gence company, in which Elon Musk and enormous amounts of data. Analyzing An appropriate legal framework is
Microsoft have stakes. Altman watches this flood of raw data would be un- crucial. But the trend toward vehicle
“We are studying how
a video with Kyle Vogt. Vogt is CTO and reasonable for accident investigation software that increasingly supports
co-founder of Cruise LLC, which is now
these sensors work authorities. At some point in the future, driving is unstoppable. ■
part of General Motors. The video is also in snow and rain, what therefore, the law will have to specify WHAT DOES A CAR SEE?
available on Youtube and shows how data they collect, which data must be stored in the car Above: Laser scan of the
Empa test track. The lab
a Cruise test vehicle drives through San and what mistakes and made accessible for investigations.
building on the left, trees on
Francisco for 75 minutes, mastering all they make.” the right, a pedestrian in front
inner-city driving situations with very Moreover, FEDRO is preparing the of the car.
Below: The Lexus was
little intervention from programmers. It approval of field tests with self-driving converted by a specialized
overtakes waiting garbage trucks even vehicles on public roads. But how can company and can also be
controlled from the back
when oncoming traffic is already in sight, to pass a vision test before getting a we judge if and when it becomes dan- seat with a game controller.
and can turn left independently at small driver’s license. Professional drivers must gerous? When do sensors fail, and when Computer screens show the
intersections even when pedestrians repeat this test on a regular basis. We do they make serious mistakes so that vehicle’s perspective.
want to cross the lane at the same time. want to develop a vision test for auton- the test would have to be aborted or
omous vehicles so they can be trusted modified? Even for monitoring such field
The Tesla fan community also published even when they’re several years old and trials, it is necessary to be able to quickly
euphoric videos in late October 2020. have thousands of miles on the clock.” and accurately assess the vision and
Some beta testers of the Tesla software the “judgment” of autonomous cars.
have received a pre-release version that The topic has not received a lot of atten- Further information on the topic is available at:
allows the car to navigate autonomously tion so far: among the more than 1,000 The project is part of a digitalization www.empa.ch/web/s504
through residential areas. A Youtuber research papers published on autono- initiative of the Swiss Competence
Youtube-Video: https://youtu.be/SHwQyKMxHpY
by the name of TeslaRaj underpins his mous driving in the past five years, only Center for Energy Research – Efficient
Photos: Empa
enthusiastic video with violin music and about 20 deal with the quality of sensor Technologies and Systems for Mobility
shows how his car stops at red lights, data. The processing of the data literally (SCCER Mobility), co-funded by Inno-
18 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 19[ FOCUS: CLEAN NEW CAR WORLD ] [ CIVIL ENGINEERING ]
KNITTING ROADS A
robotic arm lays out a also later during use. What‘s more, it Method (DEM). This should reveal the
string in a mandala-like makes asphalt susceptible to cracking displacement of individual stones and
pattern on a bed of and deformation and, on top of that, the tensile forces acting on the thread
gravel. What appears impermeable to rainwater – this too – something that cannot be investi-
to be a contemporary could be overcome. For the researchers, gated in the lab. In addition, different
art performance is basic research that it is also conceivable that rock could be patterns and mesh widths and their
explores new ways in road construc- used that is otherwise not suitable for effects on the stability of the pavement
tion. On the one hand, robot-assist- road construction, but is less rare. Last will also be examined in more detail.
ed construction techniques for road but not least, the process allows for
Empa scientists are investigating how roads could be re-
building are being tested that have so a rollable and recyclable pavement. The research of Martin Arraigada and
inforced with simple means and recycled easily after use.
far only been used in structural engi- Saeed Abbasion has not yet resulted
Their tools are a robot and a few meters of string.
neering. On the other hand, a new type A STRING AND LOOSE GRAVEL in a final product that is ready to be
of mechanical reinforcement is intend- The two Empa researchers are using used in road construction. However,
Text: Stefanie Zeller
ed to change the typical structure of various experimental setups to test solu- their research provides a lot of in-
the road surface and thus to help save tions for the above-mentioned aspects. novative potential to get closer to a
valuable resources in future or even The robotic arm plays a central role. recyclable and possibly rollable road
to recycle road surfaces altogether. It places the string in a programmed pavement with simple means. ■
pattern on the layers of gravel stacked
AN IDEA FROM STRUCTURAL ENGINEERING on top of each other. For the mechan-
The idea originates from a project of the ical tests, five of these layers of gravel
CONNECTED Gramazio Kohler Research lab at ETH Zu- and thread are placed on top of each Further information on the topic is available at:
The “Rock Print rich. Here the project was actually raised other in a test box, with the floor of www.empa.ch/web/s308
Pavilion” in Winter-
thur demonstrated as an art and research project. Pillars the box covered with a rubber mat that
how a stable piled up purely from strings and gravel fixes the whole package to the ground.
construction made
of loose stones and demonstrated that outstanding stability It simulates the deformable bed, to
strings can be cre- can be achieved by simply interlocking which the pavement is applied. The fact
ated by the “hand”
the gravel with a thread – without any that the string is exactly the same as
of a robot.
cement as a binder! Laboratory tests the one used by every Swiss citizen for
showed that gravel pillars with a height bundling waste paper shows that Empa
of 80 cm and a diameter of 33 cm can researchers are breaking completely
withstand a pressure of 200 kN, which new (and cost-effective) ground here.
corresponds to a load of 20 tonnes.
TESTS AND COMPUTER MODELING
OPTIMIZED
Asphalt also consists of rocks of various The gravel-thread package is then load-
The robotic
sizes and a binder, bitumen. Thus Martin ed with a rotating plate and with pres- arm lays out
Arraigada and Saeed Abbasion from Em- sure. This load test shows: by entangling the “knitting
pattern”. Empa
Photos: Empa, Gramazio Kohler Research / ETH Zürich / Martin Rusenov pa‘s “Concrete & Asphalt” lab transferred the individual gravel stones with the researchers are
this concept to road construction: “We thread, the package can withstand investigating
different
want to find out how a recyclable pave- a pressure of 5 kN – half a tonne – with- patterns in a
ment could be produced in the future. out the stones moving much. Normally, number of test
To do this, we are using digitalized con- the binder bitumen performs this task series.
struction methods in road construction in asphalt. Dynamic load tests with
for the first time,” explains Arraigada. rolling pressure, similar to the extreme
conditions road pavements have to
A string-reinforced road surface that withstand, are soon to be carried out.
does not require bitumen promises a
number of advantages. Since bitumen is In parallel to their lab experiments, the
extracted from crude oil, air pollutants researchers model everything in 3D on
are released during production and the computer using the Discrete Element
20 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 21[ FOCUS: CLEAN NEW CAR WORLD ] [ FUEL ]
SAVING THE CLIMATE
The latest project focuses on the produc- the filter. Using heat – around 100 °C – tium consists of partners who cover the
tion of synthetic methane from hydrogen the CO2 molecules can be released from entire value chain – from Empa research-
and CO2 – the so-called methanization. the filter. Empa researchers see further ers to energy suppliers, filling station and
WITH SOLAR FUEL
Such fuels, produced synthetically with potential for optimization in the heat fleet operators and industrial partners in
renewable energy – thus called synfu- required for this CO2 desorption. “Both the technology and plant sectors,” says
el or syngas –, can be transported via hydrogen production and methaniza- Brigitte Buchmann, member of Empa‘s
conventional routes and made available tion continuously generate waste heat,” Board of Directors and strategic head of
through the existing infrastructure. This says Bach. “By means of a clever heat “move”. The project is supported by the
is of interest for Switzerland as well as management, we want to cover the Canton of Zurich, the ETH Board, Aven-
Produced in a sustainable way, synthetic fuels contribute to switching mobility to renewable energy and to achieving globally, because it opens up an enor- heat requirements of the CO2 collector ergy Suisse, Migros, Lidl Switzerland,
the climate goals in road traffic. In the mobility demonstrator “move” Empa researchers are investigating the produc- mous potential for renewable energy. as much as possible with this waste Glattwerk, Armasuisse and Swisspower.
tion of synthetic methane from an energy, technical and economic perspective – a project with global potential. heat”. In addition to CO2, the Clime-
METHANIZATION MADE BY EMPA works plant also extracts water from Currently, Christian Bach‘s team is
Text: Stephan Kälin
The basic chemical process of meth- ambient air, which is used for hydrogen concentrating on the investigation of
anization has been known for over production in the electrolysis device. water adsorption on porous materials
100 years as the Sabatier reaction. In This means that such plants are also and the process control of the catalytic
ECO TRANSPORT “move”, another process developed fur- conceivable in regions without water reaction. Construction of the plant is
By 2030, the retailer
Lidl Switzerland ther at Empa will be used: the so-called supply, for example in deserts (see box). planned for mid-2021. “About a year
will switch from sorption-enhanced methanization. Empa later, we want to refuel the first ve-
fossil natural gas to
researchers hope that this novel process In addition to new knowledge about hicle,” says Buchmann. “With
liquefied renewable
gas to operate its engineering concept will lead to simpler technical and energetic aspects, insights methane from solar energy. ■
trucks. process control, higher efficiency and about the economic efficiency of syn-
better suitability for dynamic operation. thetic methane are one of the project‘s
prime goals. “In order to ensure this Further information on the topic is available at:
Methanization works as follows: holistic perspective, the project consor- www.empa.ch/web/s504
methane (CH4) and water (H2O) are
produced by catalytic conversion from
carbon dioxide (CO2) and hydrogen (H2).
The water is causing problems with SYNTHETIC FUELS system by harnessing surplus summer electri-
conventional processes, however: to FROM THE DESERT? city and connecting different energy sectors.
remove it, serial methanization stages When converting our energy system to However, large plants could exploit their full
are typically required – with condensa- renewable sources, there is a major challenge: potential above all in the Earth‘s sunbelt. This
tion areas in between. Due to the high renewable sources such as sun or wind are is illustrated by a simple calculation: in order
reaction temperatures, a proportion not always available everywhere. In winter we to cover Switzerland‘s energy needs during
of the water is converted back into have too little renewable energy, in summer winter not covered by hydropower as well as all
hydrogen by the so-called water-gas there is too much – in the northern hemi- long-distance domestic traffic exclusively with
shift reaction. The gaseous product of sphere. In the southern hemisphere it is the (imported) synthetic energy sources, a solar
the methanization reaction thus con- other way round. But there are also areas with power plant would be required in a desert with
M
tains a few percent hydrogen, which almost continuous sunshine – the so-called an area of approximately 700 km2; that is 27 x
obility analyses show: CO2 emissions in road traffic. Synthetic these concepts have advantages and prevents direct feeding into the gas grid; sun belt, in which the large deserts of the 27 km or, in other words, 0.008 % of the area
only a small propor- fuels from surplus renewable electricity drawbacks in terms of energy, oper- the hydrogen must first be removed. Earth are located. “From a global perspective, of the Sahara. The water and CO2 needed for
tion of all vehicles are can make a significant contribution to ation and economics. In order to use we do not have too little renewable energy production could be extracted locally from the
responsible for the such frequent driver applications. With them in a smart way, we need a deeper CO2 AND WATER FROM THE AIR worldwide, but ‘merely’ an energy transport atmosphere (see main text). “Existing trade me-
majority of the kilo- electric mobility, hydrogen mobility and understanding of the overall system,” CO2 for the methanization as well as problem,” says Christian Bach. Synthetic chanisms, transport infrastructures, standards
meters driven. We are talking above all synthetic fuels, Empa‘s future mobility says Christian Bach, Head of Empa‘s water for hydrogen production is taken energy carriers could help solve this problem. and expertise could simply be used further”,
about long-distance trucks that transport demonstrator, “move”, is investigating Automotive Powertrain Technologies directly from the atmosphere with a CO2 says Bach. So could the plant in “move” soon
Photo: Lidl Schweiz
goods all over Europe. If these continue three paths forCO2 reduction in road lab. “Together with our ‚move‘ partners, collector from the ETH spin-off Clime- Smaller plants in Switzerland can make a be a model for a gigawatt plant in the desert?
to be fueled with fossil energy, it will traffic against the background of a we are working to develop knowl- works. The system sucks in ambient air valuable contribution to the national energy
hardly be possible to sufficiently reduce rapidly changing energy system. “All edge that can be put into practice.” and CO2 molecules remain attached to
22 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 23[ FOCUS: CLEAN NEW CAR WORLD ] [ ELECTRIC DRIVE ]
ENERGY
HOUSE-KEEPING
Energy management in a house with a solar system is becoming increasing-
ly complex: when do I turn on the heating so that it is nice and cosy in the
evening? How much electricity can the hot water tank hold? Will there still be
enough energy for the electric car? Artificial Intelligence (AI) can help solve the
problem: researchers at Empa developed an AI control system that can learn
all these tasks – and save more than 25 percent energy in the process.
Text: Rainer Klose
H
ow simple it used to be: in the same time environmentally friend-
the spring, when oil prices ly way will no longer be able to rely
WHAT'S THE
took a dip, one just filled on permanently installed thermostats PRIORITY?
the basement tanks, and and manually operated buttons. What is more
important: a warm
all trouble was gone. There living room or a fully
was gasoline at every corner. All around A MULTIFACETED PROBLEM charged electric car?
the clock. Fill up, drive on, that was it. Bratislav Svetozarevic, a researcher at A smart house can
manage both.
Empa’s Urban Energy Systems lab,
With the phase-out of the fossil econo- has recognized this problem. What is
my life became much harder for smart needed is an automatic control system
spenders. Now energy prices no longer that hoards energy when it’s abundant STEP ONE: THE THEORY be ready to go. In the evening at 5 PM, STEP TWO: TEST IN A REAL BUILDING
change annually, but hourly. Solar and makes it available for expensive The solution to such problems is AI. the electric car returns to the charging Now the controller had to pass the
power is in abundance at lunchtime times of the day. The battery of one’s The Empa researcher designed an AI station with some residual charge and reality check. Svetozarevic used the
– in the evening the low sun hardly car, for instance, which is attached control system based on the principle can supply electricity back to the house NEST research building on the Empa
supplies any energy, while returning to the charging station in the garage, of reinforcement learning. When the during the night. The control system campus for this purpose. In the DFAB
commuters are causing the demand could serve as a storage device. But system acts “correctly”, it receives a was fed with weather data as well as House unit, the AI algorithm controlled
for electricity to rise rapidly. The effect Svetozarevic has to deal with a complex “reward”. Gradually the control sys- room temperature data from last year the temperature of a student bedroom
can be seen so clearly on consumption problem: every house is different, and tem perfects its behavior in this way. and had to cope with two electricity for a week. At the same time, the 100-
graphs that scientists have given it a so are its inhabitants. Depending on tariffs: expensive electricity during the kWh-sized storage battery was used to
name: the “duck curve”. When the duck both weather and season, the power Initially, the control system was only day between 8 AM and 8 PM, and simulate the battery of an electric car.
raises its head, it is getting expen- generated by the solar cells changes, simulated on the computer. The specifi- cheap electricity during the night. This time, the result was even clearer:
sive for everyone to buy electricity. as does the need for heating or cool- cations: a certain room in a building had during a chilly week in February 2020,
ing. An optimized energy control must to be electrically heated to the desired The result was amazing: the self-learning the AI control system saved 27 percent
Eying the clock when drawing energy therefore learn the daily rhythm of a temperature and maintain this temper- control system saved around 16 per- of heating energy compared to the
will thus be important for electric car house and its inhabitants – and should ature. At the same time, the system cent energy compared to a fixed-pro- neighboring student bedroom, whose
Photo: iStockphoto
drivers and homeowners. In future, also be able to react flexibly during had to supply power to an electric car, grammed solution and, in the theoretical heating was operated with a fixed-pro-
those who want to use the available operation, for example when a sudden which had to be at least 60 percent test, also maintained the desired room gram (rule-based) control system.
renewable energy in a cheap and at weather change upsets all calculations. charged by 7 AM in the morning and temperature much more accurately.
▲
24 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 25[ FOCUS: CLEAN NEW CAR WORLD ] [ ELECTRIC DRIVE ]
laying the foundation for much more:
“Our AI control system can still cope
Distributing electricity in a smart way when a photovoltaic system supplies
electricity, a heat pump and a local hot
water storage tank have to be operat-
ed – and the comfort requirements of
the residents are constantly changing”.
However, a new generation of electric
FORWARD-THINKING cars is required to be able to use the
President of The Swiss AI system for optimal energy supply in
Confederation Guy Par-
Sunshine hours melin opened the DFAB the future. Today’s standard models in
House in 2019. Now one Europe and in the US with the “CCS”
Time of the rooms serveds as
a research object.
quick-charging connection can only
be filled up, but not supply electricity.
Japanese cars with “Chademo” plugs,
on the other hand, are designed for
so-called bi-directional charging. The
Korean company Hyundai announced
in December that it would equip its
Outside temperature Electricity tariff new electric car platform E-GMP for
bidirectional charging, too. This could
help homeowners save energy in the
long term and at the same time
stabilize the electricity grid. ■
AI control system
Temperature in Electric car
hot water storage tank
Further information on the topic is available at:
www.empa.ch/web/ energy-hub
Empa’s AI control system distributes electricity from solar collectors in an optimized way.
It does not need to be programmed, but uses AI to “learn” the needs of the occupants and “The nice thing about our self-learning WORKS EVEN WITH COMPLEX BUILDINGS
Grafic: Empa / Photos: Nicolas Zonvi (2), Roman Keller
adapt to the time of day and season. It can be used for buildings of various types and sizes. AI control system is that it can be used In a next step, Svetozarevic and his
not only at NEST, but also in any other colleagues now want to determine how
When distributing energy, the occupants’ thermal comfort is the top priority. The battery of building”, says Bratislav Svetozarevic. the system can be extended from one
the electric car is used as intermediate storage and and must provide enough range in the “It doesn’t need an engineer to pro- room to larger buildings. “In our first
morning for the first trip of the day. Grid electricity is purchased when it is cheapest. gram the control system, nor someone experiment we wanted to map a typical
to analyze the house beforehand and household of the future,” says the Empa
calculate a tailor-made solution”. researcher. For the sake of simplicity,
the team has limited itself to heating
and vehicle charging. But the work is
26 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 27[ HYGIENE ]
HEAVY CHARGE
TINY PATHOGENS "We were able to show copper oxide. “Together with the ceram-
The researchers are aiming at the how virus particles attach ic, the highly porous copper layer forms
smallest of germs: tiny pathogens themselves to positively a composite material with a positively
AGAINST WATER GERMS
that – unlike the currently circulating charged and immensely large specific
charged surfaces."
coronavirus Sars-Cov-2 – are spreading surface,” says Graule. The researchers
via contaminated water and thus cause were also able to coat tiny multi-layer
various water-borne diseases such as carbon nanotubes with copper ox-
polio, diarrhea and hepatitis. Among For their investigations, the researchers ide, thus enabling virus elimination.
these pathogens is the rotavirus, which therefore chose a model virus that is
is only about 70 nanometers in size. even smaller than the rotavirus: the bac- In order to develop a cost-effective
“Conventional water filters are ineffec- teriophage MS2, which is only and sustainable filter technology, the
tive against rotaviruses,” explains Empa 27 nanometers in size – a virus that at- researchers specifically utilize materials
researcher Thomas Graule from Em- tacks bacteria but is harmless to humans. that can be recovered after use in the
Removing pathogens from drinking pa‘s High Performance Ceramics lab in Using this model virus, the scientists sense of a closed material cycle. It is also
water is especially difficult when Dübendorf. However, it is precisely these were able to show that viruses in water important that no filter components are
the germs are too tiny to be caught tiny germs that are among the most adsorb to the filter surface to varying washed out into the purified water. To
by conventional filters. Researchers common pathogens causing gastrointes- degrees depending on the water‘s this end, analytical methods for nano-
at Empa and Eawag are develop-
tinal infections. According to the World pH. “This must be taken into account safety still need to be developed so that
ing new materials and processes
Health Organization (WHO), in 2016 when developing new water treatment the most suitable composite material can
to free water from pathogenic
around 130,000 children worldwide died and filter technologies,” says Graule. be determined. At the end of the pro-
microorganisms such as viruses.
from rotavirus infections. The researchers ject, a filter technology is expected to be
Text: Andrea Six BIOACTIVE FILTERS
have now developed strategies for filtra- POROUS NANOCOATING available that is also suitable for water
Empa researchers tion technologies based on new materi- In order to develop filter technologies treatment in developing countries with
are developing novel als that cleverly circumvent the problem that can capture viruses at the nanome- their particularly high numbers of rota
filter systems made of
composite materials. of minuteness. This is because one prop- ter scale, Graule is focusing on compos- virus and other water-borne diseases. ■
Here: ceramic gran- erty of the virus particles can be used ite materials that are functionalized in
ules with a copper
for a new type of filter: the negative such a way that they specifically bind
nanocoating.
W
ater is life, biology Further information on the topic is available at:
teaches us. Reality PATHOGENS IN DRINKING WATER (0.5 to 6 micrometers), but equally potent pa- www.empa.ch/web/s201.
teaches us some- Worldwide, around 3.4 million people, mostly thogens. With a size of 25 to 80 nanometers –
thing different: children in structurally underdeveloped coun- about 100 to 1000 times smaller – viruses are
water contami- tries, die every year from water-borne diseases. the most difficult pathogens to filter out of wa-
nated with pathogens causes hundreds Among the pathogens are single-cell parasites, ter. In developing countries the contamination
of thousands of deaths each year in such as amoebae and lamblia with a size of up of drinking water with rotaviruses is particularly
places where water treatment is lacking to 40 micrometers. Bacteria such as salmo- widespread, followed by other viruses such as
or poorly functioning. To put an end to nella, which cause typhoid fever, E. coli germs the pathogens that cause hepatitis and polio.
this, the availability of clean water for and cholera pathogens are significantly smaller
all mankind has been included in the
United Nations (UN) Global Sustainabil-
ity Agenda since 2015. In accordance electrical charge of the virus particles. viruses. “In water, the surface of the virus
with this goal, Empa researchers, in Based on this idea, the researchers particles is negatively charged. We were
collaboration with their colleagues at began to develop suitable materials able to show how the virus particles
Eawag, are developing new materials that allow the adsorption of negatively attach themselves to positively charged
Photos: CDC / Unsplash, Empa
and technologies to remove patho- charged virus surfaces. Until now, it has surfaces,” he explains. For example, the
gens from drinking water, which until been difficult to create easily regener- researcher is working in an internation-
now could hardly be eliminated with ated positively charged surfaces with al team on ceramic granules made of
conventional measures, or only with high adsorption capacity, and systematic aluminum oxide, whose fine granules
expensive and complex processes. experimental studies have been scarce. are coated with nanometer-thin layers of
28 I EMPA QUARTERLY II JANUARY 2021 II # 70 # 70 II JANUARY 2021 II EMPA QUARTERLY I 29You can also read
