Insights into hydrothermally altered oceanic crust through melt inclusion analysis

Homogenized glassy inclusion after reheating and quenching.

Paper of the Month, January 2019

There are many different types of Volcano. One such are the so-called ocean island volcanoes, which include Hawaii, Iceland, Samoa, Reunion, Tahiti. The magmatic sources of ocean island basalts are believed to be derived from the lower mantle. Mantle upwellings (part of convection within the mantle) carry deep mantle materials towards the surface, causing the materials to melt, generating these ocean island basalts. Geochemists study the material of ocean island basalts to elucidate their chemical composition and its evolution in the deep mantle. In the previous studies, it has been suggested that some ocean island basalts from Cook-Austral Islands (French Polynesia) involve subducted ancient oceanic crust in their magma sources.

January’s Paper of the Month was a collaborative effort from Japan Agency for Marine-Earth Science and Technology, The University of Tokyo and Tokyo Institute of Technology. The purpose of their study was to explore the nature of volatiles in the mantle and the exchange of volatiles between the mantle and the Earth’s surface.

The major volatile reservoir in the Earth is the atmosphere and hydrosphere (Earth’s surface layer), but those volatiles came from the mantle by long-term degassing of the mantle. It is still unclear how much of these volatiles remain in the mantle and whether the exchange of volatiles occur between the Earth’s surface and the mantle, that is, outgassing from the mantle through volcanism and ingassing from the surface to the mantle via subduction of oceanic crust.

Their main finding was the exchange of Chlorine (Cl) between the Earth’s surface and the mantle. They measured volatile composition in olivine-hosted melt inclusions in ocean island basalts from Raivavae, Austral Islands. Due to the size of melt inclusions (50 to 150 micrometers in their samples), they combined several in-situ micro-analytical techniques to measure volatile elements (with secondary ion mass spectrometry) together with lithophile elements and Lead (Pb) isotopes (EPMA and LA-ICP-MS).

The Linkam TS1500 heating stage was used to homogenize melt inclusions. By using a heating stage and microscope, they were able to avoid overheating of the sample and confirm that melt inclusions did not crack or burst during the heating experiment. The implication of this work is that such subducted oceanic crust, which is eventually accumulated in the deep mantle, could be a major reservoir of Cl in the mantle. Their work suggested that subduction of oceanic crust played a significant role in moderating the salinity conditions in the ocean. Chlorine is one of the essential elements for life, but too much salinity is rather stressful. They concluded that the exchange of Cl (and volatiles) may play a key role in the evolution of life. This will be part of future studies

The group would like to expand their research target not only for ocean islands but also for island-arc volcanism, particularly in Japan where island-arc type volcanoes are prevalent. They plan to study volatiles in melt inclusions in island-arc magmas to understand how much volatiles exist before eruption and how the volatiles control the eruption style in each volcanic system.　The usage of the Linkam TS1500 is essential in these studies.

Hanyu et al., Tiny droplets of ocean island basalts unveil Earth’s deep chlorine cycle (2019). Nature Communicationsvolume 10, Article number: 60

E-skin: Understanding mechanical properties of flexible electronics

Paper of the Month, October 2018

Electronic skins (E-skins) that can mimic the functions of a human skin have been intensively studied in the past few years. They are expected to have a great impact on the upcoming generation of portable and wearable electronics related to the Internet of Things. Even after many breakthroughs in the material sciences, there are still difficulties in achieving high performance and highly functional sensors durable enough for continuous monitoring of human activity and health.

Advanced micro- and nanoscale materials within polymer-based protective layers have been successfully applied for the E-skins. However, it is not only important to study and understand the behavior and properties of these electronic materials, but also to create smart structures to achieve the desired performance for these devices.

A research group from University of Oulu bypassed common performance and functional issues by combining advanced materials and an ingenious structure to achieve mechanosensitivity to different stimuli, high sensing performance, and functionality within the device. The structure not only provided simultaneous ability to be adhered to a human skin or be attached to clothes or textiles, but also possibilities for precise tuning of the response to achieve optimal performances for different locations in the human body. The devices were able to record human activity and health in a reliable manner, providing adequate long-term durability with machine washability.

The group used a TST350 to test the tensile properties of their sample. When asked about the purpose of the stage, author Jarrko Tolvanen explained: “In our research the Linkam TST350 stage has provided a reliable way to record the stress-strain curve of various materials. Also, this stage has enabled easy and quick way of testing the mechanical properties under controllable temperature and humidity conditions, that could be proven advantageous when further improving and optimizing the performance of a strain sensor.”

However, there is still a long way to go until the commercialisation of wearable products. One of the major difficulties is to achieve a multidirectional sensor that can distinguish the types of stimuli with high selectivity but is also feasible for wireless sensing.

Although more testing is required for long-term durability and environmental stability, the group’s work is a promising start in achieving high performance wearable sensors.

Tolvanen. J, Hannu. J & Jantunen. H, Stretchable and Washable Strain Sensor Based on Cracking Structure for Human Motion Monitoring. (2018) Scientific Reports volume 8, Article number: 13241

The Role of Temeprature in Studying Slip Hydrodynamics in Polymer Melts

The movement of liquid molecules along a solid surface is called hydrodynamic slip. This event is central to understanding how fluids are transported at the smaller scales.

Between a solid and liquid interface, friction is present. When this friction is extremely high, the velocity of the fluid at this interface can be considered zero - this is called the “no-slip” boundary. This can be used to assume fluid flow at macroscopic scales, however there has been much focus in the last few decades to understand this at the more microscopic scale.

A cross-disciplinary research collaboration* aimed to develop a fundamental understanding of the physics of fluid flow. They investigated a long-standing question in fluid dynamics by trying to understand the factors that control friction at a solid/liquid interface. The group did so by conducting experiments using novel techniques that allowed them to precisely measure nanoscale fluid flow.

When discussing their experimental setup, Dr Mark Ilton said: “We use several Linkam stages in the labs, all in the THMS family. The Linkam stages provide a standardised way to thermally anneal our samples across the various labs involved in the collaboration. The simplicity, quick ramp-rates, and remarkable long-term stability are all key features. Since the viscosity of the polymeric fluids, a crucial parameter in our measurements, is highly sensitive to temperature, the precision of the Linkam stages is integral to the experiments. The size of the sample stage provided enough room to have a control sample side-by-side with a sample of experimental interest. This was a crucial part of our experimental protocol and enabled the data quality that supported our conclusions.”

Their experiments demonstrated that solid substrates that are considered “ideal” (coated silicon wafers, where the solid/liquid interactions are weak compared to uncoated substrates) can still have consequential friction due to transient adsorption of liquid molecules. This has important repercussions for products that use such coatings as they may not be as ideal as first thought.

By Tabassum Mujtaba

Bäumchen et al., Adsorption-induced slip inhibition for polymer melts on ideal substrates. (2018) Nature Communications, volume 9, Article number: 1172

*McMaster University, University of Massachusetts Amherst, University of Bordeaux, Global Institution for Collaborative Research and Education, Hokkaido University, Laboratoire de Physico-Chimie Théorique, PSL Research University, Max Planck Institute for Dynamics and Self-Organization & Ecole Polytechnique.

Cooling Rate Dependent Polymorphic Liquid Crystals

Polarised optical photomicrographs of liquid crystals show the change in texture caused by slow cooling.

Polymorphism is the existence of more than one form. In the case of liquid crystals, this is when a material can exist in two or more crystal structures. As the structures vary, this in turn affects their function and properties. Finding liquid crystal polymorphs would be advantageous for many different fields including engineering, pharmaceuticals and sensors. 

Real polymorphisms are difficult to find in rod shaped liquid crystals. Previous studies have shown that bent-core liquid crystals, although their phases can vary depending on cooling rate, havesmectic structures and x-ray diffraction patterns that are almost identical. 

A collaborative research effort from the Kent State University and Lawrence Berkeley National Laboratory found a polymorphic bent core liquid crystal that has structurally and morphologically independent liquid crystal phases that are cooling rate dependent. As their structures differ, so does the structural colour, paving way for a range of potential applications. 

The group conducted several different experiments to identify the liquid crystal polymorphs. They used Polarised Light Optical Microscopy to visualise the cooling rate dependant formation. To do so, the team used the Linkam LTS420E to conduct their temperature-controlled experiments, both heating and cooling the samples. 

They found that upon slow cooling oblique columnar phase forms and on rapid cooling, helical microfilament phase forms were produced. This change in structure was also accompanied by a unique colour change. 

This novel finding highlights the ability to control liquid crystal structure through temperature control. The change in colour facilitated by the structural transformation, could be used in future applications of thermal sensors and security tags.  

By Tabassum Mujtaba

Hegmann et al., An unusual type of polymorphism in a liquid crystal. (2018) Nature Communications volume 9, Article number: 714