Achieving mass transport control with the award-winning Stream system

Achieving mass transport control with the award-winning Stream system

The on-chip flow channel of the Stream system allows for full control over pressure, flow rate, liquid thickness and electric potential

Original article by Anne France Beker, Hongyu Sun, Mathilde Lemang, Tijn van Omme, Ronald G. Spruit, Marien Bremmer, Shibabrata Basak and  H. Hugo Pérez Garza

The liquid phase transmission electron microscopy (LPTEM) community faces numerous challenges when performing in situ electrochemical studies inside the TEM. From a lack of control over the flow and liquid thickness, to limited experimental flexibility and reproducibility, these challenges have posed considerable limitations on research. As a result, DENSsolutions has developed an in situ LPTEM solution that addresses each and every one of these challenges – the Stream system. Due to its unique on-chip flow channel design, users can effectively control experimental conditions such as pressure, flow rate, liquid thickness, electrical potential and bubbles. STEM videos are shown below to demonstrate these advantages and visualize the in situ growth of copper with multiple morphologies.

Because you can independently control the pressure at the inlet and outlet of the Stream Nano-Cell, you can control the absolute pressure in the microfluidic channel. This state-of-the-art design consequently gives you full control over the flow and the bulging of the windows, and therefore the liquid thickness. As a result, spatial resolution is improved, enabling meaningful electron diffraction and elemental mapping in liquid. You can accurately define the mass transport and control the electric potential, granting you complete access to the full kinetics of the reaction.

The in situ LPEM study

In order to exhibit the benefits of the system, copper dendrites were grown and characterized in situ. After the electrodeposition of the copper, EELS and EDS characterization were performed with copper inside the viewing area. Furthermore, high resolution images and diffraction patterns of the grown copper dendrites were recorded using the TEM.

Removal of beam-induced species

A major issue when performing LPTEM experiments with an electrolyte is the undesired influence of the electron beam. In this experiment, the electron beam interacts with the copper electrolyte. However, because you can control the flow of the liquid, you can remove or flush away any unwanted beam-induced species from the region of interest (i.e. window, sample or electrodes). This is displayed in the STEM recording below with the flow moving from right to left.

STEM movie showing debris being flushed

Bubble dissolution

It is important in LPTEM to assure that the cell stays wet. However, when bubbles form, the cell starts to dry out. The Stream system was developed with this in mind, offering a solution to this challenge. Specifically, because you can control the absolute pressure in the microfluidic channel, you can remove unwanted gas bubbles by setting the pressure high. At higher pressures, the size of the bubble decreases until it disappears and vice versa. The dissolution of a bubble that was formed during this copper experiment is shown in the STEM video below.

STEM movie showing bubble dissolution

In situ growth of copper dendrites

The growth and stripping of copper was completed a few times via cyclic voltammetry. The cycles begin with copper reduction, corresponding to the growth of the copper dendrites. Next, oxidation takes place, corresponding to the copper dendrites being stripped. Interestingly, you can see in the STEM video below that after reduction, the dendrites are thicker whereas after oxidation, the dendrites become much thinner.

STEM movie showing 5 cycles of copper growth and etching

Liquid thickness control 

In order to perform high resolution imaging, it is important in LPTEM that the liquid thickness is kept low. Aside from high resolution imaging, controlling the liquid thickness is extremely important when performing analytical techniques like EDS, EELS and electron diffraction. Ideally, the liquid should be limited below the beam broadening, which is normally expected to happen around 500nm of liquid thickness. With this in mind, we designed our Nano-Cell such that the thickness stays below the beam broadening threshold based on the spacer thickness and the maximum bulging of the windows. In the figures below, the elemental mapping and electron diffraction of the electrodeposited copper are presented. 

Elemental mapping - Anne article

EDX elemental mapping showing the spatial distribution of b) the copper dendrites and c) the platinum electrode 

Electron diffraction Annette article

TEM image of the copper dendrites on the electrode in e) and the corresponding SAED patterns in liquid phase in f)

Complete flow control

Controlling the flow also has other important advantages that are expanding possibilities in research. Namely, the ability to manipulate the flow rate allows you to control the morphology. You can see in the STEM image below that when flow is applied, the copper grows in a continuous layer with more copper being deposited. On the other hand, without flow, the copper nuclei grow isolated. This is direct proof that the unique flow-control feature of the system allows you to control the kinetics of an electrochemical reaction.

Morphology of copper with and without flow using the Stream system

Conclusively, this research highlights the unique capabilities of the award-winning Stream system, proving its potential to enable and boost research in various application fields, ranging from battery research and fuel-cells to corrosion and electrocatalysis.

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Improving the mechanical properties of 3D printed metal parts

Improving the mechanical properties of 3D printed metal parts

In situ TEM helps to understand the microstructural changes in AlSi10Mg during 3D printing and post processing

 
Original article by Mihaela Albu, Robert Krisper, Judith Lammer, Gerald Kothleitner, Jacopo Fiocchi and
Paola Bassani
Dental crown created by selective laser melting (SLM)

Dental crown created by selective laser melting (SLM)

Selective laser melting (SLM) is an additive manufacturing technique used to create unique products for the medical technique, automotive-, aeronautic- and space industry. AlSi10Mg alloy is widely used for this technique because of its low weight, corrosion resistance, good thermal properties, specific strength, and flexible post processing capabilities. The mechanical properties of 3D printed parts show better values compared to parts that are made using traditional casting of metal. But these values decrease after conventional heat treatment. In this research, scientists from Graz Centre for Electron Microscopy, Austria, tried to understand the fundamental mechanisms responsible for the drop in mechanical properties after heat treatment.
This work provides the first correlative in-situ heating multiscale analysis of the powder and the additive produced AlSi10Mg alloy, allowing a unique insight into material transitions at the micro-and nanoscale. The researchers showed that microstructural changes like crystallization of eventually present amorphous phases and the evolution of Si nanoparticles evenly dispersed in the Al-matrix are the most important factors that contribute to the enhancement or decrease of the mechanical properties.

Towards affordable 3D metal printing

Nowadays, selective laser melting (SLM) refers to the most common system used to create metal parts from powders as feedstock. Despite its popularity, powder based additive manufacturing is still an expensive process, and consequently, getting proof components at the first attempt is of great economic interest. Manufacturers of such parts strive for optimizing their processes, not only to improve material properties, but also to enhance the interchangeability of building platforms and thus, their economic flexibility. Controlling these production aspects and finding an adequate post-processing strategy helps to fine-tune the microstructural features, and therefore the mechanical properties, according to different application fields.

Low magnification HAADF STEM video 80°C to 360°C in 20°C steps for the as-built sample, maintaining the isothermal stages for 4 min each
Atomic resolution video of a Si nanoparticle in the Al-matrix during in-situ heating

Benefits of in situ STEM

In-situ heating experiments in scanning transmission electron microscopes (STEM) enable immediate information about the structural, morphological and chemical changes and are thus helpful for the selection of various post-processing strategies.

DENSsolutions Wildfire System TF FEI

The DENSsolutions Wildfire H +DT system enabled the fast heating and cooling that allowed us to perform nanoscale crystallographic and chemical analyses at certain temperatures that corresponded to the exothermic peaks in DSC measurements and to the in-situ XRD measurements.

Dr. Mihaela Albu
“In-situ heating experiments performed on 3D printed materials enable breakthrough advances in printing and post-process optimization. DENSsolutions Wildfire system proved to have superior thermal and spatial stability, ensuring high-resolution investigations at higher temperatures.”

Dr. Mihaela Albu
Senior Scientist | TEM at the Austrian Centre for Electron Microscopy and Nanoanalysis

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EUSMI Nanostars Project

EUSMI Nanostars Project

Nothing could better illustrate the excellence of EUSMI Joint Research Activity (JRA), than the Nanostars project, which has combined the expertise of three EUSMI partners from three distinctive areas: CIC biomaGUNE, EMAT and DENSsolutions.

Nanoparticles are a versatile functional material and have much potential in medical applications. The chemists at CIC biomaGUNE have successfully synthesized a novel type of nanoparticles, targeting at cancer diagnosis and therapy. For this, it is crucial to obtain a precise understanding of the particle morphology, especially at high temperature. The electron microscopy experts at EMAT in Belgium have come to help and taken up the challenge to visualize the nanoparticles.

This challenge is formidable but also pushing the frontier of the electron micrsoscope technique. A new component must be developed and implemented into the existing machine. To achieve this, EMAT has jointed force with engineers and experts from DENSsolutions. In the video, you will see how the trio has produced a masterpiece of solution and extended the scientific and technical know-how.

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Stream LPEM system wins the Microscopy Today 2020 Innovation award

Stream LPEM system wins the Microscopy Today 2020 Innovation award

A conversation with our CTO Dr. Hugo Pérez-Garza who has been leading the development of the award winning system.

DENSsolutions is one of this year’s winners of the Microscopy Today Innovation Award. At the 2020 Microscopy & Microanalysis Virtual Meeting, DENSsolutions Stream LPEM system has been recognized as one of the ten most innovative products of the year.

We interviewed CTO Dr. Hugo Pérez- Garza to learn exactly how the Stream system convinced the jury of its high degree of innovation that makes new scientific investigations possible. Below you will find a transcript of the video interview.

Congratulations on winning the award. Can you tell us how you felt when you first heard the news?

It was great to hear that we were selected as the innovation of the year. This is something that confirms not only the level of innovation that the team has been bringing up, but it also helps us to confirm our leading position in the market. So it’s been really great.

Who were the people you first shared the news with?

As you can imagine, the first people that I shared this with were the R&D team members. As soon as I heard about this innovation award, I immediately called for a meeting so that I could tell everyone about it. None of this would have been possible without the ongoing effort of everyone within the R&D team. So they were the ones who deserved to know first. And of course, to me, it’s been a privilege to have the chance to lead what I consider as a world class R&D team.

Can you tell us about the innovative aspects that made it earn the reward?

Yes, this is all thanks to the different components that make up the Stream system. We’ve got the nano cell, the holder, our pressure based pump and of course the hardware that allows us to introduce the stimuli.

The nano-cell has a patented design that allows us to have on-chip inlet and outlet so that we can have a well-defined microfluidic path. We have the holder that has a modular design so that you can disassemble the tip at any point, do some thorough washing, you can put the tip in a sonicator, and because you can remove the tip, you can also replace the inner tubing at any point so that you can prevent cross contamination or clogging. And then we have the pump that, as opposed to current solutions that are out there which rely on a syringe pump that only pushes the liquid via the speed of the stepper motor, in our case, we can control the actual pressure of the liquid. So because we can combine this with our current nano-cell, by independently controlling pressure at the inlet and outlet, we can control the absolute pressure inside of the fluidic channel and therefore enjoy a very well-defined, pressure driven flow. And then we have the heating control unit and the potentiostat that allows us to introduce either the heating or biasing capabilities.

Why did you guys develop this system to start with?

Before the Stream system, we used to work with the so-called Ocean system, which is the predecessor of the Stream. Back in those days, we started realizing, together with our customers, that one of the most important things to address was to prevent relying on diffusion as a way of getting the liquid into the region of interest where the window and the sample is located. So after discussing a lot with experts and people in the community, we realized that it was important to make sure that we wouldn’t be bypassing the chips in the so-called bathtub design, which is the same design that not only our predecessor system used to have, but also other systems out there are still relying on. So making sure that you can prevent the bypass of the chips, making sure that you can therefore control the mass transport was something that ultimately gives you the benefit of controlling the kinetics of your experiment at any point.

What are the main benefits of the system?

Because we can control not only the pressure and the flow, there’s a lot of things that basically start from that point onwards, which are the fact that since you can control the liquid thickness, you can control, for example, the possibility of avoiding the beam broadening effects that the electron beam typically suffers from when you are working in liquid. If you can achieve that, then that means that you can start providing meaningful electron diffraction capabilities, meaningful EELS capabilities. You can do elemental mapping in liquid. And the fact that we still preserve that flow and pressure control at any point allows you also to start getting other very important benefits, such as the capability to mitigate away unwanted bubbles. You can even dissolve the bubbles at any point, or you can flush away beam induced species.

So when you put it all together, it really results in a very strong system that addresses the main issues that the community has been facing. The modular design of the Stream holder allows for flexibility as it prevents cross contamination or clogging when changing experiments. The system allows you to have a reproducible flow through your region of interest at any point. And you can manipulate the sample environment to your own convenience as you are able to control all the parameters that are around it.

Who contributed to the development of this system?

You can imagine that the Stream system was the result of a multidisciplinary work. We had to call in our main expertises in-house. We see MEMS development as our core competence. But MEMS is something that is very complex, that involves different areas. So we have people with a lot of expertise on the mechanical engineering area, on the electrical engineering area, material sciences, physics, chemistry and biology. But of course, the system, as I mentioned before, is not only the MEMS, but also the holder, the pump. So there’s a lot of mechatronics development in there. You can imagine that, of course, there’s a lot of microfluidics fluid dynamics.

So overall, it was a highly multidisciplinary work that, together with the expertise and the advice that we got from our customers, allowed us to put it all into one strong system that is now being able to address many of the issues that they all had.

Are customers already working with the system?

Yeah, absolutely. Ever since the launching of the system, by now, we have a very good amount of systems that are installed in the field where people are working in all sorts of application. Like material sciences, life sciences and energy storage. And we see that this system has been able to take over the work that they attempted to do for many years before. But due to the limitations that their previous systems had, they were never able to achieve. Now, with the Stream system we see and we hear directly from the customers that they’re finally able to start speeding up with the research and the results that they always wanted to get. So it’s a great feeling for us to know that the value is really there.

Who are the people that will benefit most from this system?

Of course, the Stream system finds its applications in a wide variety of opportunities. On one side, people in material sciences, people interested in, for example, nucleation work, in chemical production processes where it is very important not only to control the kinetics, but also to control the temperature. That’s where the Stream system finds one of its core values. On life sciences of course, people who are interested in working with either fuel cell analysis or biomolecule analysis where it is very important to try to mimic as much as possible physiological conditions like 37 degrees of body temperature. Controlling the environment and keeping these samples in its native liquid environment. That, of course, opens up a lot of opportunities for people in these kind of fields. And people who are doing research on energy storage, for example, people trying to develop the next generation of batteries where it is really important to understand how the battery works. What are the best conditions to prevent, for example, dendrite growth that might lead to short circuit. People working on fuel cells, people working on corrosion. There’s really a wide variety of electrochemical applications where the Stream also brings some big added value.

Can you tell us something about what future developments lie ahead?

Despite the fact that our current Stream system is already addressing most of the important issues that the LPEM community wants to avoid, we still remain very self-critical on our own developments and we keep analyzing what the main areas of opportunities for our system still are. And by now, we have already identified additional steps that we can take further. So we’re working very hard on new developments that I think are going to be really exciting. So stay tuned, because in the upcoming months, we can expect some very nice announcements on future developments that are coming.

Thank you for reading, to learn more about our Stream system please follow the links below.

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In-situ imaging provides detailed insights on the dynamics of SMSI induced overlayer formation on catalyst particles

In-situ imaging provides detailed insights on the dynamics of SMSI induced overlayer formation on catalyst particles

Enabled by DENSsolutions Climate system in correlation with other TEM characterization techniques

Original article by Arik Beck, Xing Huang, Luca Artiglia, Maxim Zabilskiy, Xing Wang, Przemyslaw Rzepka, Dennis Palagin, Marc-Georg Willinger & Jeroen A. van Bokhoven.

Noble metal nanoparticles stabilized on oxide supports are an important class of catalysts that are used in many applications such as fuel cells, exhaust gas treatment and energy conversion. It is well known that an interaction occurs between the nanoparticles and their oxide support which affects the catalytic activity called ‘strong metal-support interaction’ (SMSI). SMSI is a surface phenomena in which the migration of partially reduced oxide species, from the oxide support, covers the nanoparticle and thereby alters the chemisorption and catalytic properties. It can give rise to desired synergistic effects and increased selectivity. Now, using in situ TEM combined with other analytical techniques and theoretical modelling, researchers at ETH Zurich have been able to create a real time view of the SMSI phenomena.

Controlling the sample environment

Reductive pre-treatment of catalysts by heating, resulting in SMSI, has been known to alter the selectivity of oxide supported nanoparticles since the late 1970’s. However, the exact influence of the different parameters like temperature and gas concentration were still unknown. But now, thanks to the DENSsolutions Climate G+ system, researchers are able to determine the immediate effect of these parameters in increasing detail. The Climate G+ system provides a nano-reactor, containing the catalyst sample, that can be placed in any TEM* and gives the researcher unprecedented control over the sample environment in terms of temperature and gas parameters.

The in situ TEM experiments performed for this research required multiple switching between hydrogen and oxygen environments at 600 °C. This made the Climate G+ system, that is used on the JEM-ARM 300F at ETH Zurich, ideal for this research.

Evolution and dynamic structural changes of the overlayer in SMSI. A platinum particle on a titania support in the first exposure to H2 at 600 °C (a,b) and the subsequent atmosphere change to O2 at 600 °C (c), a switch to H2 (d) and then a switch to O2 again (e), and interpretation of the phenomena based on the combined results of in situ transmission electron microscopy, in situ X-ray  photoemission spectroscopy, and in situ powder X-ray diffraction (f–j). Insets for c–e show a magnified image of the overlayer structure observed. Scale bar is 5 nm.

Correlative techniques

In situ TEM, using gas and heating, is a powerful characterization technique to obtain atomistic, real time, information about the SMSI phenomena. To derive a holistic view of SMSI and the role of hydrogen and oxygen within this process. The in situ TEM results have been combined with ambient pressure XPS and in situ powder XRD experimental results. Finally, theoretical density functional theory (DFT) modelling was used to support the conclusions about how SMSI actually works.

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New article about the Stream Liquid Heating system

New article about the Stream Liquid Heating system

Published in Journal of Materials Chemistry C

Original article by J. Tijn van Omme, Hanglong Wu, Hongyu Sun, Anne France Beker, Mathilde Lemang, Ronald G. Spruit, Sai P. Maddala, Alexander Rakowski, Heiner Friedrich, Joseph P. Patterson and H. Hugo Pérez Garza.
We are proud to announce a new publication in the Journal of Materials Chemistry C, in which we collaborated with our customers to observe the temperature dependent etching behavior of silica particles inside the TEM. The paper discusses the design of the Stream system and how it allows to control the solution conditions inside the Nano-Cell. For this experiment, we were particularly interested in the comparison between in situ LPEM data and ex situ data from more traditional methods.

According to the reviewers

“In this manuscript, the authors provided a new design of MEMS based liquid flow system with a unique on-chip microfluidic channel and a microheater, which enables the quick replenishment of fresh solution and uniform heating of the liquid solution.”

Connecting in situ to ex situ

One of the most fundamental challenges that any microscopist experiences is the question whether the phenomenon you observe inside the microscope is representative of what happens outside. You can see interesting things happening inside the microscope, but if there is no link to the outside world, the knowledge is not so useful.

To solve this challenge, we design our products so that the user has full control of all the relevant parameters during the in situ experiment. In the Stream system, this relates to controlling the solution conditions. Especially temperature and concentration. The sample should experience the same conditions inside and outside the TEM. To achieve this, the Stream system has a flow channel that enables rapid replenishment of the solution to ensure continuous supply of fresh reactant species. Meanwhile, the microheater accurately controls the temperature.

Temperature control

Temperature is a highly important variable to control. For this reason, all our product lines include the possibility to manipulate temperature. In liquid, the speed of chemical reactions is often dictated by the temperature. Moreover, completely different reaction pathways can be found at different temperatures. During an in situ experiment, the increase in temperature can be used to trigger a phenomenon. Many people rely on the electron beam to induce the dynamics. However, it’s normally desirable to decouple the stimulus from the imaging. In other words, the beam is used for imaging, while the MEMS device supplies the heat to start a reaction.
We chose to design the MEMS device to generate a uniform temperature throughout the Nano-Cell. In other words, no temperature gradients are present that could lead to complications. This also allows to accurately measure and control the temperature of the liquid and the sample.

Temperature dependent etching kinetics of silica nanoparticles in-flask vs. in situ LPTEM, showing good similarity between both situations. Time = reaction time.

Silica nanoparticle experiment

To validate the effect of the combined flow channel and microheater, we looked at the etching process of silica nanoparticles in NaOH. This process is quite sensitive to temperature; increasing the temperature substantially accelerates the reaction kinetics. In-flask, the etching time in NaOH with pH 13.8 is reduced from ~500 to ~10 minutes when increasing the temperature from 20 to 60 °C. This was found by measuring the transmittance of the solution. The TEM allows us to observe this process in real time, at the nanoscale. In the Stream, we aimed to reproduce the reaction conditions from the in-flask experiment. In the flask, the bulk liquid acts as a large reservoir of available reactant species, while in the Nano-Cell, the space is much more confined. A constant flow was used to refresh the solution to make sure that the silica particles are etched by fresh reactants continuously.
We found very good similarity between the results obtained in-flask and in situ. In the Nano-Cell, the etching time reduced from 360 to 4 minutes for the same temperature increase from 20 to 60 °C. So in both cases, the same order of magnitude increase in etching rate is observed, indicating that the Nano-Cell meticulously mimics the situation outside the microscope. This was the most important finding from the paper. The e-beam seems to slightly accelerate the etching process, but the low dose imaging procedure ensured that the effect of the e-beam was reduced to a minimum.

“The most exciting part of the Stream holder is that the control it offers over temperature and flow means that we have access to a completely new phase space to observe dynamic processes, this will undoubtedly result in the discovery of new nanoscale phenomena and lead to innovations in materials synthesis.”
Dr. Joseph P. Patterson
Department of Chemistry and the department of Materials Science and Engineering,
University of California, Irvine, USA

Collaboration with customers

DENSsolutions actively participates in the scientific community. We work closely together with our customers to make sure that our products help them to generate impact. This study is a good example where our expertise in the design and engineering of the in situ system was combined with the expertise at TU Eindhoven and UC Irvine.

In Eindhoven they were already very experienced working with the silica nanoparticle samples and with the ex situ etching behavior at different temperatures. So when the MEMS devices for Stream Liquid Heating were launched, they proposed to run this experiment inside the microscope. We anticipated that one of the key parameters to control during the experiment would be the e-beam, as it could interfere with the etching process. Fortunately the groups at Eindhoven and Irvine have a thorough background in imaging soft matter, so we managed to adhere to a low dose imaging protocol to successfully minimize the beam effect.

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