Materials Connect

Using adsorption science to gain insight into some key characteristics of a materials scientist

Recently I’ve been mentoring a PhD candidate through their first ever manuscript to be submitted to a journal which involves determining porosity of a material with a heterogeneous pore structure. The technique we were using relied on adsorption of nitrogen at 77 K on to the surface of pores within the material. As we went on this journey, I got the impression that we had very different approaches to our work and this made me question what it takes to be a scientist: the attitudes and behaviors that come so easily to some do not seem to manifest in others. What does it mean to be a scientist and how has this influenced materials science?

We are curious

Science is about following the evidence, asking why, and finding information on the things you don’t understand. We design experiments to investigate these things and improve our understanding. We base that investigation on a question. When we design an experiment, we think about all of the factors that could affect the outcome and we decide how we can control them. We carefully consider all of the details while drawing on our experience and scientific instinct. We are careful and thoughtful.

Dewar and Ramsay appear to be the first to report on the sorption of nitrogen and other gases at low temperature. Their separate studies, reported in 1905 and 1906, focused on the composition of the atmosphere and the separation of noble gases. Their simple curiosity about the air around them kicked off a whole series of experiments that ended up being very useful for analyzing porous materials.

We strive for understanding

Science is personal. It’s about developing your own understanding and passing it on to others. Rather than glossing over the details, pretending that they’re not important to us and that someone else will take care of them, we leap on the details and turn them over in our minds; we examine them from all angles to decide their importance in our experiments. We push them together with other details and look at how they fit together. We search books and journals to help us with the details and then list everything that we still do not know. 

After the first reported gas sorption studies in the 1900’s, Langmuir went on to develop a model for ideal localized monolayer adsorption (1916) that later allowed Brunauer, Emmet and Teller to publish a theory which supported the calculation of surface area (1938). Later, the Kelvin equation was used by Barrett, Joyner and Halenda to arrive at a very popular method for finding the pore size distribution (1951). The work of one scientist or group built on the work of another, each body of work inspiring someone to ask a new question.

The International Union of Pure and Applied Chemistry initially categorized adsorption isotherms into 6 different types (King et al, 1985), which was recently refined to closely relate them to pore structures (Thommes et al, 2015).

We are transparent and honest

We make assumptions. Once we’ve pulled together this vast body of knowledge, collected by hundreds of scientists over many decades, we look at what is still unknown and as ourselves what is logical: following all of the evidence, what could be a sensible possibility? We state these assumptions clearly and loudly so that others can understand our reasoning. We invite others to test our assumptions. We communicate our logical argument with straightforward prose, carefully defining our assumptions.

Langmuir very clearly pointed out that his model relates to a flat plane where all adsorption sites are uniform. Similarly, Brunauer, Emmet and Teller specified that their theory assumes that the completed monolayer is made of close-packed spheres. For nitrogen, each sphere is usually said to cover an average area of 0.162 nm². To calculate the Brunauer-Emmet-Teller (BET) surface area, the theory should only be applied to a part of the adsorption isotherm that matches some consistency criteria, and these criteria depend on both the adsorbent and adsorptive as well as temperature. To determine pore size, we assume that the pores are rigid and all of the same simple shape with the curvature of the meniscus dependent only on the dimensions of the pores. It is generally agreed that this method is not applicable to micropores (<2 nm in width) and only applicable to macropores (>50 nm) if the conditions can be extremely well controlled.

Rearranging the BET equation allows a straight line to be plotted so that the BET parameters can be found. The section of the isotherm to which the BET fit is applied must meet the consistency criteria, indicated on the graph by the red data points.

 

We use high-tech equipment and know how it works

Much of this understanding, scientific evidence, theory and basic physics, and even some assumptions are packaged into high precision instruments – tools that we can use to delve even deeper into science and answer yet more challenging questions.

There is a plethora of equipment out there that will automatically program nitrogen sorption at different relative pressures, and will even calculate the BET surface area and pore size distribution. These results should be carefully scrutinized. Many will default to applying the BET theory to relative pressures of 0.05 – 0.35, but of course, you should check the applicability to your material before relying on the default calculation.

 

To sum up: We are curious; we are inspired. We are scientists.

 

This article draws on a review paper by Kenneth Sing “The use of nitrogen adsorption for the characterization of porous materials”, Colloids and Surfaces A: Physicochemical and Engineering Aspects 187–188 (2001) 3–9 as well as various forum discussion on ResearchGate.

 

Gold extends the exfoliation of 2D materials to a large range of compounds

A two-dimensional (2D) material such as graphene is highly versatile. It can be wrapped up into zero-dimensional fullerenes, one-dimensional nanotubes, or stacked into three-dimensional graphite. Such 2D materials emerge as the building blocks for all other applications and now researchers are on a quest to diversify the family of the ultrathin 2D materials.    

This quest to diversify the materials options is demanding. The success requires an industrial-scale method that produces high-quality 2D crystals. Many approaches have been developed but most of them are limited in yield, lateral size and contamination. At present, the preparation of 2D crystals can be categorized into two methods, bottom-up and top-down approach, depending on the direction in the production.

Category I – Synthesis from bottom to up

Epitaxial growth and chemical vapor deposition (CVD) can produce thickness-controllable 2D graphene crystals with a desirable, large single crystal (millimeter scale). However, the quality suffers from scalable growth for many other materials using the synthesis methods, particularly for heterostructured materials. 

Category II – Thin it down production

Liquid-based ion-intercalation and liquid exfoliation are used as one of the top-down methods. By immersing bulk crystals in the liquid, the strength that holds the adjacent layers together in the crystals decreases. With forces applied to the layers, either by sonication or rapid mix, the additional shear force would push the layers apart. Yet, as chemical methods, the solvents often contaminate the 2D products.  

Mechanical exfoliation has been a unique top-down production method of emergent 2D materials. As the origin of the successful 2D graphene, mechanical exfoliation, also known as the scotch-tape method, produces the most high-quality thin layer with few defects due to the absence of chemical processing. While mechanical exfoliation often suffers smaller sizes (from a few microns up to 100 microns) of 2D crystals, a group of researchers believes that they can improve the method by identifying suitable substrates that firmly adhere to 2D flakes without losing the structures and properties.  

 

Au assisted mechanical exfoliation for 2D materials

A new study, published in Nature Communication in May 2020, demonstrated a gold (Au)-involved mechanical exfoliation that successfully isolated 40 different 2D materials as single crystals, including transition-metal-dichalcogenides, metal trichlorides, black phosphorus and magnetic compounds. 

Au is known to have a strong affinity for chalcogens, especially to sulfur atoms that lead to the self-assembled monolayer. In exfoliating 2D crystals, Au serves as a substrate to hold and adhere to the topmost layer of a bulk crystal. The group VIA chalcogens (S, Se, Te) and VIIA halogens (Cl, Br, I) at the terminated surface in most 2D materials interact strongly with Au, thus enabling the adhesion between Au and the crystals. 

The authors used the scotch-tape method in making the 2D material. Once the bulk crystal is brought in contact with the Au deposited substrate, gentle pressure is applied on the tape to establish a crystal/Au contact. Peeling off the tape removes the majority of the crystal, leaving one or a few large-area monolayer flakes on the Au surface. 

The thickness of Au requires only a few nanometers. This thin layer of Au can be applied on a variety of substrates such as silicon wafer, transparent quartz sapphire, and flexible plastic films, demonstrating the versatile applications.

 

(a): The Au-involved mechanical exfoliation process. A thin layer of Au is deposited onto a substrate covered with a thin Titanium (Ti) layer (magenta) that facilitates the adhesion. Then, a cleaved bulk crystal on tape is brought in touch with the Au layer. Peeling off the tape will result in the 2D flakes on the Au surface. (b)-(d): Limited only by the size of bulk crystals, the 2D flakes are at millimeters size. The exfoliated 2D materials can sit on (b) substrates of SiO₂/Si wafer, (c) transparent sapphire and (d) flexible plastic substrate, demonstrating the versatility of applications. (e): This Au-involved substrate method is compatible with CVD-grown 2D materials, such as MoS₂.

 

(f) to (g): Optical images of the resulting large exfoliated 2D crystals. The highlighted red box is hardly accessible using other mechanical exfoliation methods at the present technique. (bottom): heterostructured MoS₂/WSe₂ with Raman spectroscopy characterization.

 

The systematic studies on the efficient exfoliation assisted by an Au adhesion layer to a layered crystal provide access to a broad spectrum of millimeter-sized monolayer materials. The high quality of the exfoliated monolayers, one benefit of the mechanical approach, along with the large-area 2D flakes can support the exploration of the ultrathin 2D materials. 

With the improved reliability to extract atomically thin crystals, the size of the resulting 2D layers would depend on the quality of bulk crystals. As in the successful silicon technology, the extraction of wafers from large, high-quality single silicon crystals has been key. For industrial applications of 2D materials, the focus of materials research may shift toward yielding high-quality layered crystals.

 

Chiung-Wei Huang acknowledges Tianyu Liu, Laura Leayn and Hortense Le Ferrand for the thoughtful suggestions.

The importance of feedback for information sharing: insights from a comedy club and materials science

My favorite comedy club in Manchester, UK, has – like so many other organizations operating during the Covid-19 pandemic – converted to working online. Normally a comedy club would have a stage, a microphone and a live audience but the online format means that the audience is silent and faceless. One of the most common responses of the comedians is that it’s really difficult to perform when you don’t know how your performance is being received: just how funny are you? This experience made me think about how scientific information is passed on from one person to another.

When you’re new to public speaking, giving a lecture to a big room full of people can feel a bit like hurling information into a void, an experience that sounds quite similar to those of the comedians in the online comedy club. However, even though many universities have also switched to giving lectures online, the lecturers have an advantage over the comedians: they can get feedback from the students, either through surveys or through marking assignments.

In a normal face-to-face lecture I find it very helpful to split the lecture up into small sections and ask the students to do a short assignment in between, usually in small groups. The assignments often involve using some specific software and it’s very helpful for me to be able to walk around the room, check progress and offer help. Trying to do the same thing over video-conference seems very daunting! The software, known as TRIM, calculates how an ion with a given energy will interact with a material and produces some visual representations of ion tracks that are great for aiding understanding. I’m so used to simply pointing at the screen in a situation where both the lecturer and students can use gesture and facial expressions to infer meaning that I know I’m going to need to think hard about how to adapt the lecture this fall.

The TRIM software is part of the Stopping and Range of ions in Matter (SRIM) package and provides a wealth of information about an energetic ion interacting with a target material. It’s a very visual way of getting to grips with radiation damage which makes it great for a demonstration in a lecture.

Gestures and facial expressions are some ways of gaining feedback, and this is incredibly important for checking scientific understanding. Imagine having a conversation with someone where you’re explaining something that is new to the other person. You’d probably start with the simplest thing and you’d get a response from the other person. You’d then start gradually building up the complexity and information would pass back and forth, each interaction adding a layer to the sphere of knowledge until you both arrive at the same level of understanding. Along the way the other person will ask questions, seeking clarification and letting you know that they are interested in what you have to say. This shared understanding becomes an organic thing; it grows depending on how you both interact with each other.

The model for communication, developed by Shannon and Weaver (The Mathematical Theory of Communication, University of Illinois Press, 1949), explains that the two people involved in communication must interact if the message is to be understood.

The same organic method of knowledge sharing happens with the written word too. In writing this blog, each author gets feedback from the other bloggers which points out sections that were difficult to understand. The feedback is incorporated into the final published version. This also happens in the peer review process when a manuscript is submitted to a journal.

Giving a lecture, or a stand-up comedy show, to a faceless audience that may be distracted by the cat can be a somewhat surreal experience. Feedback is an essential component of communication; without it, we are just shouting into a void: an exercise that is tiring and, ultimately, pointless. So perhaps now is the time to adapt and do something new to get that same feedback and make sure our science is still heard and understood. One useful adaptation I have noticed when using video communication is that, since I can see my own facial expressions and gestures, I can get an idea of how the others might be receiving my non-verbal communication and I can then modify it on-the-fly to create a more meaningful experience.

Emojis have long been used for communicating feelings online and can also be incorporated into video-communication. In a lecture, they could be used to check that the audience understands what is being said, or maybe to alert the lecturer to something isn’t quite right. In this way, a virtual experience can be even more enriching than a face-to-face one.

Moving a lecture, or indeed any performance or type of communication, to a purely virtual world also means that it can be recorded. This makes it easy to review our own lectures and find ways to make improvements, or to select parts of the lecture to create a mini-series.

Some of these features may work very well for small audiences but how good could they be for a class of a hundred people or more? Would we need to consider one approach for a small audience, and a different approach for a much larger one? Experience, gathered and shared by the entire online community over time, will guide us. In the future, perhaps we can imagine a world where virtual reality makes it feel like you’re attending a real-live lecture where the speaker can move through the audience and interact with individuals.

COVID-19: From my home office to yours – we’re in it together!

Like many folks around the world, MRS staff - since March 16^th - has been working from home in order to stem the spread of the 2019 novel coronavirus.

From our home offices, we’ve been covering materials-related COVID-19 news such as a podcast episode on the development of a microneedle array that is key to a skin patch that delivers a vaccine, and a webinar on how materials research can counter the pandemic.

Researchers on COVID-19 are working at breakneck speed that it’s actually difficult to keep up with all the news! We’ve captured some of the more relevant news articles and linked these on the MRS COVID-19 Information and Resources page. This is where we also keep updates regarding the MRS Meetings for 2020.

Stay safe! Stay well!

-Judy Meiksin

Materials playlist for Valentine’s Day!

Here is a playlist for songs with a materials edge, based on the titles & lyrics.

• STARSHIP Nothing’s gonna stop us – durability, resilient (sustainability)
• The Partridge Family I can feel your heartbeat – mechanical properties, 3D bioprinting
• SHAED Trampoline – stretchable, phase transformation, gold
• Olivia Ong I feel the earth move – tribology, biomaterials
• Charlie Wilson Forever valentine – sustainability, biomaterials, acoustics
• Elton John Something about the way you look tonight – optical, solar energy, microscopy
• Dengue Fever Tokay (lyrics) - biomimetics
• Captain & Tennille Love will keep us together – adhesion, microscopy
• Dolly Parton & Kenny Rogers Islands in the stream – quantum dots, plasmonics, nanoparticles, polymers & soft materials
• Tammi Tarrell & Marvin Gaye Ain’t no mountain high enough – topological insulators, biomaterials, fast transformations (ferromagnetic domains)
• Joe Cocker & Jennifer Warnes Up where we belong – crystal growth, hierarchical, defects, renewables
• Melissa Ethridge & Cam Come to my window (lyrics) – infrastructure, transparency, catalytic, extreme environment
• “Zanna, don’t!” (musical) I think we got love – characterization
• Ariana Grande & John Legend Beauty and the beast – ductility, durability
• “West side story” (musical) Tonight – carbon, sustainability
• From “Grey’s Anatomy” My funny valentine – biomaterials, morphology
• Rihanna Stay - thermodynamic, life cycle assessment, circular economy
• Barbra Streisand & Kris Kristofferson Evergreen (lyrics) - sustainability
• Lionel Ritchie & Diana Ross Endless love – biomaterial, hybrid, optical, strength

-compiled by Judy Meiksin

Finding universality in diversity

Allometry is a branch of science that studies the relationship between sizes and properties. This is an old and well-established field that was initiated in the early beginning of the 20^th century with the book from D’Arcy Thompson “on growth and form”.

Opposite to isometry where the size of an organism or a biological trait scales proportionally to a property, allometry is usually expressed by a power law: Y~m^b, with Y the property, m the mass (or size) of the organism, and b a scaling exponent, usually a multiple of ¼. Typical examples of scaling laws are the metabolic rate  with b ~3/4 or lifespan  with b~1/4 [1].

Establishing general laws from empirical data is an old approach of science, best practised by Galileo Galilei [2]. Since then, the Descartes’ method has spread over all fields of science, emphasizing instead the use of physical laws, the drawing of hypotheses and experiments to confirm them [3]. Yet, starting with the observation may lead to discovery of new principles and still presents interest and opportunities in modern science. This is particularly true for biomimetics and bio-inspiration, two trendy topics at the moment. Indeed, it is acknowledged that there are still many unknown in the natural world and that understanding how biomaterials, biological structures and biological organisms work could lead to new engineering ways to solve current challenges.

It is therefore not surprising that allometry is regaining popularity today. To give an example, the determination of scaling trends between the mass of birds and their bone length in the wing, the spacing of the feathers or their microstructural lengthscale, provides insights for the design of energy-saving aircrafts [4]. Similarly, the scaling laws between the weight and the density, the width or the height of the little pads from the hairs that insects and mammals use to adhere to surfaces is useful to design attachment devices [5].

What is even more exciting about allometry and scaling laws is that the methodology can be applied beyond biology and the mass/size of organisms. For example, Pierre Gilles de Gennes, Nobel laureate, used this scaling concept in polymer physics [6]. This was truly disruptive since polymers used to be characterised solely by their chemistry, and not through their length, branching etc.

Even more unusual, scaling laws can be established between proteins and stiffness, such as between the collagen content and the stiffness of cells, as well as between proteins and genes, such as between the nuclear protein Lamin-A and the gene coding for collagen, COL1 [7]. Finally, scaling laws can also be applied to find trends in publication’s impact factors and citations…[8].

There are thus many opportunities to find universality behind diversity.

 

Further reading:

[1] GB West, JH Brown, The origin of allometric scaling laws in biology from genomes to ecosystems: towards a quantitative unifying theory of biological structure and organization, The Journal of Experimental Biology 208, 1575-1592 (2005).

[2] D Dubarle, La méthode scientifique de Galilée, Revue d’histoire des sciences et de leurs applications 18, 161-192 (1965).

[3] E Denissoff, La nature du savoir scientifique selon Descartes et l’Histoire de mon esprit, autobiographie intellectuelle, Revue philosophique de Louvain, 66, 5-35 (1968).

[4] TN Sullivan, MA Meyers, E Arzt, Scaline of bird wings and feathers for efficient flight, Science Advances 5, 1-8 (2019).

[5] E Arzt, S Gorb, R Spolenak, From micro to nano contacts in biological attachment devices, PNAS 100, 603-606 (2003).

[6] PG de Gennes, Scaling concepts in polymer physics, Cornell University press (1979).

[7] J Swift,  IL Ivanovska, A Buxboim, T Harada, PC Dingal, J Pinter, JD Pajerowski, KR Spinler, JW Shin, M Tewari, F Rehfeldt, DW Speicher, DE Discher, Nuclear lamin-A scales with tissue stiffness and enhances matrix-directed differentiation, Science 341 (2013).

[8] H Dong, M Li, R Liu, C Wu, J Wu, Allometric scaling in scientific fields, Scientometrics 112, 583-594 (2017).

 

 

Materials song list for New Year’s

Earlier this year I put together a song list for summer picnics, identifying songs with a materials edge. For New Year’s, I searched for the same but came up short.

The materials motif I notice for New Year’s songs includes a lot of sustainability & renewable energy with a fair amount of materials chemistry; some metals & alloys, polymers, photonics, silicon dioxide, and mechanical properties; then smithereens of Au, phase transformation, metamaterials, ceramics, crystalline structure, fatigue, graphene, solar energy, membranes, transparency, magnetoresistive random-access memory, and space materials.

Well, okay, that sounds like a lot.

But the problem is that all of these are a real stretch. I match silicon dioxide to one line: passin' round the bottle; ceramics to cup of kindness; metals & alloys to ring in the New Year; and polymers to glitter.

The rest is even a greater stretch: magnetoresistive random-access memory to a mention of memories. Any words related to an ending (of the old year) and a beginning (of the new year) – sustainability. 

From a writing-point-of-view, songs about New Year’s (that I found) carry very few metaphors. This makes me want to come up with some New Year’s lyrics myself – maybe a project for next year!

It’s a great set of songs, though; so here’s the list. Happy New Year’s!

Taylor Swift New Year’s Day (polymers, magnetoresistive random-access memory)

Mariah Carey Auld Lang Syne (materials chemistry, ceramics)

Prince 1999 (lyrics) (materials chemistry, sustainability)

Eagles Funky New Year (lyrics) (silicon dioxide, phase transformation)

U2 New Year’s Day (Au, renewable energy)

Bon Jovi New Year’s Day (metals & alloys, organic materials)

Regina Spektor My dear acquaintance (Happy New Year) (lyrics) (SiO₂, mechanical properties)

Europe The final countdown (space materials)

Sugarland Maybe Baby (New Year’s Day) (lyrics) (photonics)

Goo Goo Dolls Better days (sustainability)

Death Cab for Cutie The new year (crystalline structure, fatigue, graphene)

Pentatonix New Year’s Day (polymers, materials chemistry)

Otis Redding and Carla Thomas New Year’s resolution (lyrics) (metamaterials)

Ella Fitzgerald What are you doing New Year’s eve? (lyrics) (metals & alloys)

B.B. King Bringing in a brand new year (lyrics) (space materials, sustainability)

Van Morrison Celtic New Year (transparency, materials chemistry)

A Great Big World This is the New Year (NOW what’s next!) (solar energy, membranes, mechanical properties)

-compiled by Judy Meiksin

What do you mean by “data”? What do you mean by “share”?

Sara Laura Wilson, an undergraduate student in the Department of Materials Science and Engineering at the Massachusetts Institute of Technology (MIT), posed this inquiry to 6 materials researchers. Three of the scientists head research labs at MIT and three at Imperial College London.

“Their divergent viewpoints illustrate the challenge of openly sharing experimental materials science data,” Sara says.

Working with Micah Altman, director of the Center for Research on Equitable and Open Scholarship at MIT, and Rafael Jaramillo who leads a research group on electronic materials at MIT, Sara developed a list of survey questions targeting these 3 areas of data management:

• attitudes about sharing data
• data sharing practices
• data stewardship practices

It is indeed daunting to think about how the materials research community will move to data sharing when responses to this small set of questions can vary just among a handful of researchers.

Materials Connect: How did you come to choose principal investigators (PIs) from the Boston area and from London?

SARA: When this project began in February 2018, Professor Jaramillo referred me to PIs at MIT who’ve expressed prior interest in data management and sharing. The project continued over the following year, during which I studied abroad at Imperial College London in the Department of Materials. Professor Jaramillo also had a contact at ICL, through whom I was connected to other faculty at ICL. While all faculty I interviewed performed work related to materials science, their fields of study were very diverse. Through the interviews, I learned of the divergent perspectives on data sharing across materials research.

Materials Connect: What surprised you about their responses?

SARA: All PIs believed that data-sharing should be required, but they had mutually incompatible views of what and how much data should be shared. There was also little uniformity of data management practices beyond the use of Dropbox or a similar database. In general, day-to-day activity was managed by the individual researcher, who did not have set management guidelines, thereby making data searching and interpretation by a third nearly impossible.

Materials Connect: What are a few key outcomes from the survey?

SARA: There are clear needs for improved data management tools, but transitions will remain difficult due to the diversity of hopes, expectations, and current practices in experimental materials science. We need a common set of expectations for data sharing—one that is more nuanced than current requirements but sufficiently general so different researchers could use different software tools to comply. These could be developed by a convening of publishers, materials scientists and their member organizations, research librarians and administrators, and other stakeholders.

Materials Connect: What are your recommendations from here?

SARA: Based on this analysis, data sharing should be comprised of two components. The first is the broad adoption of basic file-level data sharing at the time of manuscript submission. The second component is software for managing data during research. The data management system should require minimal documentation for saved information that can enable data sharing at the time of article submission to become seamless. Despite the groundwork needed for these recommendations, I am hopeful about the future of open materials science. By starting conversations among researchers within and between universities, through both studies like this and other works, the need for data sharing and management systems will be realized. The potential benefits will, hopefully, minimize the burden of undertaking this transition.

Sara and her advisors report on their survey in an article forthcoming in the MIT Undergraduate Research Journal; a preprint, however, is available now: “Methods for open and reproducible materials science.”

-Judy Meiksin

The G-filter: The simple high tech solution to India's water pollution

As Abdul Rajak Khan kneads the clay for his Gravity Filter, the sights and sounds of the village are all around him.

Loose brown soil drifts from the ground floating over unplastered red brick buildings. 

Copper bangles clatter as women pound hard mud with a bat, breaking it down to powder the consistency of dust. 

It is even in the way Abdul says ‘Mitti achchi hai’. The soil is good. It has salts which give it strength, and whiteness that has come to define pottery from Jodhpur. 

Like most cities in the Indian state of Rajasthan, Jodhpur is a dense panoply of palaces and forts set in the stark landscape of the Thar Desert. The dry season lasts the whole year with meager rains supplying most of the water for nearly a million people, in addition to livestock. 

Much of this water also happens to be polluted with heavy metals, fecal matter, and bacteria such as E. coli that cause diarrhea. 

The G-filter that Abdul is preparing is a homemade solution that promises clean affordable drinking water to the Indian rural community.  

From the outside, it looks like any other garden variety flower pot, a wheatish brown frustum that fits inside another bucket. On a good day, the G-filter can produce up to a liter of pure water every hour that is then collected through a tap attached to the outer vessel. 

While ceramic filters are quite common all over the world, the G-filter is made by local Indian potters through indigenous technology using only locally sourced raw materials. In Jodhpur, the scientific effort to study and standardize the filter is led by Prof Anand Plappally and his graduate students Sandeep Gupta, Amrita Kaurwar, and Raj Kumar Satankar from the nearby Indian Institute of Technology (IIT) Jodhpur. 

“In India, there is a potter in every village. Our goal is to help them create effective water filters using techniques that they are familiar with,” Prof Plappally tells me over the phone. “We don’t need to teach them much about the traditional manufacturing process - they have been doing it for years.” Instead, the research team helps them in selecting suitable raw materials, fine-tuning specific processing parameters, and in final product testing. The wares are shaped using a locally manufactured molding press. “The potter sells his products in the nearby market, thus avoiding transport costs. Not only does the overall health improve but also the economy,” Prof Plappally says.

His graduate student, Amrita Kaurwar, who led much of the material studies, says, “What differentiates the G-filter from other ceramic filters is that it is made in open earth kilns within potter households from raw materials that are locally available at Jodhpur. This includes sawdust from the local carpenter's shop, salty clays, oxidizing matter from bajri (saltpeter), and marble dust.” 

Marble is one of Rajasthan’s major exports. The white marble used to construct the iconic Taj Mahal was quarried from Makrana, a mere 150 miles from Jodhpur. 

“The salts decrease the temperature at which the filter needs to be baked, reducing the fuel bill. The burnt calcium carbonates help in killing harmful bacteria such as E Coli and is effective to a lesser extent in removing heavy metals such as arsenic. The filtered water has no traceable amount of pathogens and is the best option that most villages currently have,” Amrita says.

Amrita now lives in Pune, a large city in the southern state of Maharashtra where she moved with her husband and son after she obtained her PhD degree in March 2019. 

Oddly, the "village" is here too: It is in the indistinct clamor of the street vendors whose voices unceremoniously cut into our phone conversation. 

India and its villages are deeply intertwined, like a crab and its shell. They share similar destinies and sorrows, what is home and shelter is also what limits mobility and growth. 

Most of the water in the country is severely polluted with microbial growth many times above what would be considered scandalous in the Western world. The Ganges River in the north carries upwards of 9 billion liters of industrial waste and sewage every day. Most of the rivers are clogged with plastic, chemicals, and feces. Potable drinking water is fast becoming not just an urgent civic concern but also a major political issue. The southern city of Chennai, one of the major metropolitan cities of the nation, is facing the worst water shortage in its history and 7 million residents are pointing fingers at local politicians. 

The lessers rivers, cities, and villages are no exception. Bacteria such as E. coli that cause diarrhea and even death are widespread. 

Now that she is the mother of a four-month-old, the quality of drinking water is very much on Amrita’s mind as she explains how the G-filter works. “The pores of the filter are between 10 nanometers and 1 micrometer. These pores are too small for the bacteria to get through.” 

Interestingly, without the marble dust, the E Coli filtration rate is 99.99%. With marble, this increases to 99.999%. At this rate, it is virtually untraceable. 

Much of Amrita’s work has been to detail the scientific nature of the filters and to quantify the filtration parameters. She has established among other things that the filter works best at an ambient temperature of 35°C, even though the drop off on either side is minimal. She has studied the role of other additives such as iron in the ceramic body. The results suggest that iron improves the removal of arsenic. 

A major part of their work has been to measure how effective the filter is in removing microbes. This was done through the setup shown in the figure. Ambient water is spiked with a known strain of E. coli and is allowed to pass through the filter. The number of cells pre- and post-filtration is carefully calculated which yields the rates mentioned before. 

Schematic of microbial filtration set up. From Gupta et al, International Journal for Service Learning in Engineering, Humanitarian Engineering and Social Entrepreneurship, Vol. 13, No. 1, pp. 53-66, Spring 2018

Thanks to their efforts, the G-filter is taking a life of its own and is becoming popular not just in Rajasthan but also in faraway states such as Bihar, Kerala, and Tamil Nadu. This is in no small part due to the work of NGOs such as Rupayan Sansthan, Enactus-IIT Madras and the S M Sehgal foundation that has come forward to promote the product.

The potter can sell fully functional filters with clay storage containers priced at around 600 Indian rupees or roughly ten US dollars. 

A typical filter can last anywhere from six months to a year with an occasional cleaning. The NGOs take no part of the profit. They teach the technique to local potters and help standardize their wares. The potters sell them wherever they like. 

The research group working on the G-filter has more than 10 publications in journals and books, with more in progress. 

But the real reward, both of them assure me, is in the villages across India where their work will translate to good health, happiness, and prosperity. 

______

Watch Rajak Khan make the G-filter in the following video. 

 

 

 

Where were you when Apollo 11 landed on the moon?

Three space experts react very differently to the July 20, 1969 Apollo 11 landing in this video:

The producers of this video, released 10 days ago by Nature, do a fantastic job, I think, of capturing very different takes in science communication. They could have simply held up a microphone and ask, “Where were you when Apollo 11 landed?” and, of course, some of the interviewees they could have chosen may not even have been born yet. So they might have modified their question and ask, “What do you think about the 50^th anniversary of this landing?”

The producers, however, do much better. They film two researchers and one aviator as they watch film footage of the actual landing. The camera focuses on the women, but includes a box in the top corner that shows us viewers what they’re seeing.

Watching the NASA film footage elicits reactions from the women that would not have been possible with simply a mic and a question.

As the film footage shows the landing

Sara Russell (researches planetary materials): I can see the dust starting to come up now, so it’s actually very hard to see anything on the surface….

Marissa Lo (studies lunar volcanology): You can see that they’re just sort of landing onto an area with absolutely no craters….

Wally Funk (aviator): He’s being told what to do when you’re coming down for a landing. It’s just like when I’m coming in for an aeroplane landing.

Isn’t this cool as each interviewee notices something related to her specific interest?

As the film footage shows the astronauts on the moon

Marissa Lo (lunar volcanology): He’s describing what the surface is like here, so this would have been the first time that someone has seen what the lunar regolith is like. So the lunar regolith is like the soil that’s on top of the surface of the moon….They’re collecting a core tube sample. We do this for a lot of rocks and, actually, glaciers on Earth as, say, ice or rocks are deposited over time, that’s recording a history as you’re going deeper into the ground.

Comments after watching the NASA film footage

Sara Russell (planetary materials): And we’re still studying these rocks now, 50 years later ….Before Apollo, we had no idea how the moon got there….This giant impact of a Mars-size body into the Earth that smashed into it and then splashed material out that coalesced to form the Moon.

Wally Funk (aviator): You can’t jump from there to Apollo. You have to learn to fly, you have to learn to fly jets, and you have to understand how the gravity works.

Sara Russell, leader of the Planetary Materials Group at the Natural History Museum, London, was only 2 years old during the landing. Marissa Lo, PhD student researching lunar volcanology at the University of Manchester, was not born yet. And Wally Funk, aviator, was part of the Mercury 13, a privately funded Women in Space Program.

By choosing representatives from 3 generations, the producers provide a range of reactions.

Furthermore, by asking them to watch the film footage, the producers elicit very detailed responses that correlate with their fields, enabling them to continue giving detailed impressions afterwards.

Now, for your reading pleasure, science writer Omar Fabián published this article about a materials researcher receiving a briefing in Houston, 1969, about the moon rocks they’ll be studying. The researcher was sort of not interested until he heard the word lexan….

-Judy Meiksin