Prof. dr. Kees Jalink
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“A main aim in basic cancer research is to unravel the differences between normal cells and cancer cells. These differences might then be exploited in the hunt for specific cancer vulnerabilities: any trade that is exclusive for cancer cells might give us leads on how to attack cancer cells while leaving healthy cells untouched”, explains Prof. dr. Kees Jalink of The Netherlands Cancer Institute in Amsterdam (NKI).

Today Prof. dr. Kees Jalink shares his story about the research the ‘Biophysics and Advanced Imaging Group’ the NKI (The Netherlands Cancer Institute) is working on and the role of flow meters and controllers in their research.

Biophysics and Advanced Imaging Group

Unraveling these differences between normal cells and cancer cells has proven a difficult task because most cancer cells are for 99.9% like healthy cells. In the Biophysics and Advanced Imaging Group, we zoom in on cells using advanced microscopy techniques, including live-cell imaging, fluorescence microscopy and “functional imaging” techniques. In the latter, tricks like Fluorescence Resonance Energy Transfer (FRET), Fluorescence Recovery After Photobleaching (FRAP) and Fluorescence Correlation Spectroscopy are used to extract information about proteins (biomolecules) and their interactions in single living cancer cells.

Image description Photo Jalink Group | Composite living cells NKI

Living cells yield much more information

Not too long ago, for visualization by high-resolution microscopy, cells were typically killed, fixed, stained for specific components and embedded in resin. However, imaging living cells yields much more information:

  • living cells may go through division
  • migrate
  • interact to form tight monolayers just like living (cancer) cells in our body Only with living cells, we can get a grasp of the dynamics of the internal biochemical processes.

A whole range of colored Fluorescent Proteins (picture 1) are available that enable us to label a single protein species and learn what we want to know about that protein. The trick is, to keep those cells alive and healthy on the microscope.

A two-color photomicrograph of a few cells through the microscope

A two-color photomicrograph of a few cells through the microscope

On the microscope, cells are kept in a glass bottom dish filled with DMEM medium: a bloodplasma-like salt solution with vitamins and nutrients. In the early days, we just kept them at room temperature in dishes in free air (~20 % O2, 80 % N2, 0.05% CO2). However, that does not mimic the atmosphere in our bodies at all, and consequently, results were not as expected.

For example, cells typically refused to divide and most cells died after 1-2 days. Also, control of pH in the medium appeared next-to-impossible. Therefore we needed to set up a dedicated incubator that houses the cells and most of the microscope. In this incubator, the air needs to be warmed to 37°C, moisturized and the atmosphere must be different from air:

  • it must contain at least 5% CO2
  • and the % of oxygen must be adjusted between ~2 % and 20%

This is to resemble the various oxygen tensions encountered in the body. For example, solid tumours are well known to be hypoxic (contain less than a few % of O2) and this completely alters the physiology of the cells, as well as their response to anti-cancer drugs. Read the process solution in our customers application note.

But how to achieve precise atmospheric control?

At a exhibition we learnt about Bronkhorst and their mass flow meters and controllers. With assistance of Bronkhorst Nederland, we have chosen three thermal mass flow controllers of the EL-FLOW Select series and hooked them up to the outlets of compressed CO2, N2 and air present in our lab.

The rest was simple: by adjusting the relative gas flows with the mass flow controller, we can now set CO2, N2 and O2 levels to all the relevant values. These ranges are 2-19 % for oxygen, 0-20 % for CO2 and 80 – 100% for nitrogen.

Ever since, we have carried out all our experiments under such controlled conditions and the results have been much more consistent -and also much more relevant- due to this incubator. We have used it to investigate how cancer cells migrate during metastasis and how they can penetrate layers of other cells and survive in this ‘niche’. We also used it to explore how cells use chemical signals to communicate with each other, and how these signals are received and subsequently processed within the cells, in detail.

Bronkhorst instruments in experimental setup

Bronkhorst instruments in experimental setup

The µ-Flow liquid mass flow controller comes to the rescue

As it goes in science, solving one problem led to the identification of another. We noted that at 37°C, the medium evaporated more rapidly, leaving the cells dry after a few days unless we tightly closed the imaging dish. But that restricts access to the cells, it makes it impossible to add growth factors, hormones or cancer drugs for our studies during the experiment.

Moisturizing the air only partly solved that, because at high humidity, condensation formed that might damage the sensitive electronics in our setup, and we therefore had to remain below 60 % relative humidity. Again, mass flow controllers provided a simple and reliable solution. We selected a µ-FLOW mass flow controller for liquids to supply a very stable flow of deionised water. Using a local BRIGHT controller with PiPS (Plug-in Power Supply) allowed us to control water influx between 0.5 and 9.6 microliter per minute.

Empirically we found that with the valve adjusted to 1.3 ul/min, we completely compensated for evaporation, and we are now capable of keeping cells alive for weeks on the microscope. The system has been very-low maintenance: simply install, and forget about it, so that we can focus on our core business. The mass flow controllers have been pivotal in constructing the microscope incubator, and the cells, they divide and develop happily.

Read and learn more about this application ‘Accurate flow control for cancer research’ from our customers experience. • Check out our instrumentsused in this application: µ-FLOW mass flow controller, EL-FLOW Select mass flow controller and BRIGHT controller

• Read more about this research on the website of The Netherlands Cancer Institute, NKI.

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Lynn Woerts
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2020 is a few days old and the plans and goals of this new year are starting to take shape. Let’s look back on last year. What did we achieve? Which blog post was the most fun, useful, gripping or interesting to you? Oh and by the way, we’ll assure you that we’re going to share all our knowledge about low flow, mass flow and flow meters even more often this year. From the overview of the 2019 statistics, we’ve come up with a top 5 of most popular blog posts.

  1. How to deal with vibrations using Coriolis mass flow meters
  2. Do you know why Mass Flow reference conditions matter?
  3. Real-time pressure and temperature compensation to optimize flow control
  4. Flow Meter Accuracy & Repeatability
  5. Flow control valves; the most used accessory in flow control

Top 5 most popular blog posts in 2019

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1. How to deal with vibrations using Coriolis mass flow meters A Coriolis mass flow meter is known as a very accurate instrument and it has many benefits. To be quite frank we were quite surprised that this blog post came in first place. In industrial applications, all kinds of vibrations with different amplitudes are very common. However, the question is whether these vibrations influence the measuring accuracy of a Coriolis mass flow meter. Ferdinand Luimes, Liquid Flow Technologies product manager, shares the advantages as well as the disadvantages of these flow meters and provides some handy hints in using these instruments.

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2. Do you know why Mass Flow reference conditions matter? The world of flow measurement applies reference conditions, which can be further divided into standard reference and normal reference. Another distinction is between European and American style. Chris King, Bronkhorst USA General Manager, sheds light on this apparently complicated construction in his blog post, detailing exactly what the differences are and explaining why these reference conditions matter.

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3. Real-time pressure and temperature compensation to optimize flow control This blog post topped the charts in 2018 and is still in the top 5 today, once again proving the relevance of this topic. As it turns out, various external factors can have an influence on the measurement accuracy and control stability of mass flow controllers. Vincent Hengeveld, Gas Flow product manager, explains the theory behind real-time pressure and temperature compensation.

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4. Flow Meter Accuracy & Repeatability Choosing which flow meter is right for your application is a pivotal element in its success. Generally speaking, the two important statistics are flow meter accuracy and repeatability. In his blog post, Chris King explains what these two parameters mean and why they are crucially important.

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5. Flow control valves; the most used accessory in flow control Finishing the list is a blog post about control valves, perhaps the most often used accessory in flow meters. A control valve is used to control a flow by varying the size of the flow passage. Do you know which valve is best for your flow meter? Stefan von Kann, senior engineer in applied physics, provides a number of tips and tricks for the most pressing areas of attention.

2019 guest bloggers

We wish to thank our guest bloggers very much for their fascinating studies and compelling stories. It fills us with pride that you contributed content to our website in 2019.

• Roland Snijder, medical physicist resident at Haaglanden Medisch Centrum (NL), worked as a researcher on the multi-infusion project at the department of Medical Technology & Clinical Physics of University Medical Center Utrecht. In his guest blog, he focuses on investigating physical causes of dosing errors in multi-infusion systems. • Jean-François Lamonier (University of Lille) is an expert in the catalytic treatment of volatile organic compounds. In this blog post, he explains how his team uses flow meters for this purpose. • Jornt Spit, researcher at the Radius research group at Thomas More University of Applied Sciences in Belgium, has a background in biochemistry and biotechnology. He is working on renewable biomass. Read his blog post on controlled CO2 supply for algae cultivation and its valuable contribution as an alternative source of carbon. • Prof. Michaela Aufderheide (Cultex Technology GmbH) has been working in the field of cell-based alternative methods with a focus on inhalation toxicology for more than 30 years. Increasing pollution of the environment and workplaces demands new testing methods. Read her blog post: ‘The e-cigarette – A blessing or a curse?’

Would you like to become even more inspired? All blog posts can be read on our website.

On behalf of the entire Bronkhorst team, I wish you a healthy, wonderful and innovative 2020!

Which topic would you like to be the focus of a blog post in 2020?

Dion Oudejans
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Semiconductor chip technology is enhancing our lives in many ways. Emerged from semiconductor technology, MEMS chip technology is also present in devices around you in the form of sensors. Think of your smartphone that captures your voice and senses the smartphone position, orientation and movement by means of Micro Electro Mechanical Systems (MEMS). Adding those features is barely impacting the physical dimensions of a smartphone: it still fits in your hand and pocket.

This blog is about instrument miniaturization by MEMS chip technology and the benefits of miniaturized gas flow instruments for application in the field of gas chromatography. As a MEMS Product Manager at Bronkhorst High-Tech, I can see the benefits of miniaturization by MEMS technology in such applications.

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IQ+ FLOW solution based on MEMS modules

Miniaturization by MEMS chip technology

Further miniaturization is achieved by combining MEMS modules in customer specific flow solutions.


In a laboratory environment, it is advantageous to work with desktop-sized equipment. Advantages of increasing functionalities in table top equipment are: reduced space requirements, enhanced ease of operation and often reduced cost of ownership.

Gas chromatography equipment is a good example of a concentration of functionalities on a small footprint. Many types of gas composition and vapour composition can be analysed with high accuracy and for very low concentration levels. Additionally, there is a certain degree of automation involved. This is all within arm’s reach of a laboratory analyst.

Gas chromatography

The goal of gas chromatography analysis is to identify and measure the concentration of gas components in an analytical gas sample. Within the gas chromatograph (see picture 3), there is often a need for gas flow or pressure control. The picture shows a gas flow controller for the carrier gas stream (red) and a pressure controller for the split flow stream (yellow).

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The principle of gas chromatography involves a controlled carrier gas stream that passes an injector, column and detector. A sample gas is injected for a short period of time, creating a gas sample plug. The gas sample plug is separated into gas components across the column, which become visible as peaks during detection.

Picture 4 shows an example of a gas chromatography output.

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Headspace sampling

Let’s zoom in on dynamic headspace sampling that is used in combination with gas chromatographys. Headspace sampling refers to the gas space in a chromatography vial containing a liquid sample. The liquid sample is a solvent, containing material to be analysed. E.g. volatile organic compounds in environmental samples, alcohols in blood, residual solvents in pharmaceutical products, plastics, flavor compounds in beverages and food, coffee, fragrances in perfumes and cosmetics.

This is explained in picture 5. Dynamic headspace sampling is performed by purging the gas space and the adsorbent. The adsorbent collects the sample gas. After transport, the adsorbent is purged again to release the sample gas into a gas chromatograph.

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Where a gas flow controller comes into play is at purging the headspace with a constant Helium or Nitrogen flow for a pre-determined period of time at a specified temperature between 10 - 200 °C. The gas flow, containing the headspace sample gas, passes an adsorbent that collects the headspace sample gas.

The adsorbent is usually made of Tenax TA material. Now, the adsorbent is transported to the inlet of a gas chromatograph. While the adsorbent is heated between 20 - 350°C, a controlled Helium or Nitrogen gas flow passes the adsorbent to release the headspace sample gas into the inlet of the gas chromatograph. The gas chromatograph does its job to analyse the sample. Different signal peaks in time show the different components and their concentration.

IQ+FLOW gas flow meters and pressure controllers

For flow instruments, a number of specifications are important in headspace sampling and gas chromatography in general. The IQ+FLOW product line addresses these specifications with small instrument size, fast response, good repeatability, low power, low cost of ownership and the excellent support that you can expect from Bronkhorst.

Read more about the IQ+FLOW chip based product line

For more information about gas chromatography in combination with IQ+FLOW flow and pressure meters and controller have a look at our application note ‘Gas Chromatography'.

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The future of MEMS technology

Bronkhorst is committed to look ahead and find applications that can be enhanced with MEMS chip technology. Feel free to contact us for questions. We will keep you informed!

Read more about MEMS technology in our blog 'Miniaturization to the extreme: micro-coriolis mass flow sensor'

Kevin van Dijk
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For most people the classic summer treat is ice cream. Around 7 billion gallons of ice cream and other related frozen desserts are produced every year worldwide, with production peaking (as you might expect) in the summer months, according to the International Dairy Foods Association. Yet, the moment you consume an ice cream, you will probably not wonder how this delicacy is being made. To get that perfect ice cream, a mass flow controller is often used.

What does ice cream have to do with mass flow meters?

Ice cream contains many different ingredients, such as fat, sugar, milk solids, an emulsifying agent, flavouring and sometimes colouring agents. But there is one main ingredient that you may not have thought about, probably because you can’t see it—air. Ice cream is made by freezing and simultaneously blending air into the ingredients. So why is air so important?

If you have ever had a bowl of ice cream melt, and then refroze it and tried to eat it later, it probably did not taste very good. Moreover, if you leave a carton of ice cream out in the hot sun and let it melt, the volume of the ice cream would simply go down. Air makes up anywhere from 30% to 50% of the total volume of ice cream, therefore, aeration in the production process is crucial.

The amount of air in ice cream (often called overrun) affects the taste, texture and appearance of the finished product. Higher aeration will produce a tastier and smoother ice cream. A side effect of adding air to ice cream is that it tends to melt more quickly . Thus, for attaining an optimal structure of the ice cream, it is important to have a stable inlet air flow in the production process with a constant cream/air ratio. This can be achieved by using a mass flow controller.

The process of whipping ice cream into shape

To guarantee the right consistency and structure which ensures a full flavoured ice cream, the cream must contain the correct proportion and composition of air bubbles. Hence, aeration mixer manufacturers use a mass flow controller to dose an exact amount of air into the cooled mixer. Such a mass flow controller will ensure a continuous air delivery, proportional to the cream flow . The mass flow controller must be capable of maintaining its performance regardless of any possible back pressure variation. Occasionally, a check valve is mounted downstream of the mass flow controller. If inlet pressure drops, such valve will avoid ice back stream into the instrument. A pressure meter is also used with the purpose of monitoring the inlet pressure.


The SEM (Scanning Electron Microscope) picture below shows the ice cream microstructure. Air bubbles are a critical ingredient. Experts claim its optimal size, distribution and quantity are one of the secrets for having a creamy texture recipe. Hence, according to meet such demands, Bronkhorst has provided efficient solutions for enhancing continuous aeration processes.

Ice cream structure

So, the next time you head to the ice cream parlor with your friends, be sure to keep in mind the importance of Bronkhorst when it comes to that delicious refreshment.

EL-FLOW select

  • Watch the video about the EL-FLOW Select to learn more about the thermal mass flow instrument which can help you create ice cream.

Want to stay up to date on new flow solutions? Every month the latest tips in your e-mail box.

Hans-Georg Frenzel
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We all love cake, there’s no denying that, and especially with whipped cream. A celebration isn’t a celebration without a cake, whether you’re throwing a birthday party or attending a wedding. Or just when you’re having coffee with friends or family, simply because it’s delicious. Baking and decorating a cake takes a lot of time and patience. And that’s exactly why most choose the easy way of picking out an already finished piece , either from their local pastry chef or out of the freezer section at the supermarket. And today I would like to tell you something about how such a fancy cake is made.

Manufacturing the cake layers

It all starts with the base, which consists of one or more layers of cake that provide support to the whipped cream. These layers are factory produced, but they aren’t made in individual round spring forms. The dough is applied on a closed metal conveyor belt by using nozzles. This belt goes through an oven and at the end the individual shapes with the desired diameter are cut out of the dough.

Controlling air by using mass flow controllers

To make sure that these cake layers all have the same weight and consistency, foam technology is used in addition to the baking agent in the dough. In this case, a foam mixer generates a dispersion of dough and air which is then applied onto the baking steel belt. In this process, it is highly important that this dough always has the same consistency, density and quality. Thus it is not only necessary to control the delivery rate of the dough, but just as important is the amount of air. By using the Bronkhorst EL-FLOW Select mass flow controllers, precise control of the required air volume is ensured at all times throughout the whole process.

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Whipped cream

In cake decoration, the cake layers are covered with whipped cream and other sweet fillings. To produce whipped cream out of liquid cream, another foam mixer is used in combination with Bronkhorst mass flow controllers, proving their worth yet again by achieving continuous high accuracy and precise control. The whipped cream production is similar to dough production; however the requirements for this system are different.

Hygiene requirements: Cleaning in Place - CIP

In food production, high hygiene requirements apply. In the dough production process, the mixer is cleaned of residues by CIP (Cleaning In Place) using cleaning additives, guaranteeing a hygienic product. However, in whipped cream production, it’s highly important that all product-contacting surfaces in the foam mixer are clean and absolutely germ-free, since it’s a sweet dairy product and the cake needs to be preserved for a long period of time. This asks for even higher hygiene requirements, so these machines need a different cleaning approach. Using only CIP with cleaning additives can’t guarantee this, so they have to be sterilized in place (SIP) as well. Using a saturated steam at a temperature of 130° Celsius, the product area of the machine is thoroughly cleaned. This maintenance takes around 300 seconds to make sure all germs are killed. This gives the cake a longer shelf life when stored in the refrigerator or freezer.

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Hansa Mixer

Hansa Industrie-Mixer is a worldwide, medium-sized company that operates in the field of mixing machines and foam generators for the food and non-food industry. Technical equipment before and after the foam mixer is also included in the scope of delivery to the customers. These are not mass-produced products, but every system is customized and tailored to the needs of the customer. If you want to differentiate yourself from the competition, you need a custom-made machine and system. The heart of the foam mixer is a mixing head that uses the rotor/stator principle. Rotor and stator are fitted with rings of pins which are able to pass the pins on the opposite side when the rotor rotates in the stator. The generated turbulence and shear forces produce a fine dispersion from a pumpable medium and a foam gas, which in this case creates the used foam.

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Read more about aeration in Bronkhorst’s success story on how mass flow meters are important for adding the correct proportion and composition of air bubbles to ice cream.

James Walton
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Miniaturization is a trend you see in our daily life. The tiny house movement is something very popular at this moment, people choosing to downsize the space they live in by moving to a tiny house with an average space of 100-400 square feet. But also in industry miniaturization is a hot item. Mass flow meters and pressure controllers with minimal footprint fit this trend.

Footprint reduction

Having worked in both the Life Sciences and Analytical industries I am sympathetic to the ever increasing demands for small foot prints and faster instruments. It has been a continuing trend for many years that lab real-estate has become more and more expensive; this led to a drive for footprint reduction of instruments. You had to make sure that size didn’t make you expensive in bench space.

One of the drivers behind this process was the NeSSI system initiative (New Sampling/Sensor Initiative), sponsored by the Centre for Process Analysis and Control. The aim was to reduce the overall costs of engineering, installing and maintaining chemical process analytical systems. In the NeSSI system, mass flow meters and pressure controllers needed a standard footprint of 1.5’’.

Footprint of Mass Flow Meters and Pressure Controllers

This footprint is perfect for a large number of applications and end users, even for some of the Life Science OEM companies that have room to spare in their systems. However, when you are re-designing your system and you have the chance to incorporate new technologies, look at the placement of existing technology and maybe add more. It helps if you can reduce the footprint of the components that you use even further.

Reducing the footprint of a known, working technology has challenges of its own. The design and function of which will be driven by the physical characteristics of the measurement principle and therefore the sensor that it uses. To change this you need to look at alternative measurement technologies as a way to achieve the end goal of the industry, same functionality, same signal, smaller package.

Mass Flow Meters and Pressure Controllers for minimal footprint

Working in conjunction with the TNO, the Netherlands organisation for applied scientific research we designed a new range of mass flow meters and pressure controllers built around MEMS technology. This allowed us to offer solutions with a footprint of 0.75’’, halving the footprint and offering ultra-compact flow controllers.

Have a look at our blog MEMS technology to support compact gas chromatography equipment to read more about miniaturization by MEMS chip technology.

This has given our customers:

  • Compact assembly ensuring space efficiency
  • Analog or digital communication
  • Top mount and side ports modules, easily accessible
  • Pre-testing ’Plug and Play’ manifold assemblies, reducing customer test requirement

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To maintain the usefulness of the new instrument you have to have the same functionality. Along with a sensor on a chip, we need a new, smaller control valve, filter options and a smaller pneumatic shut-off valve. To save even more space and build time, customers requested a down-ported version.

The final addition that makes full use of the space saving created by the addition of new technology was to create a manifold system where a customer can design a number of flow channels into a manifold, all well within the internal space limitations they have for their instrument.

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This is one of the key themes of our blogs and it is referred to time and again. The Solutions based approach, ending up with a bespoke solution not a standard product with compromises. Innovation in technology must be driven by the customer. If you do not think that a standard flow or pressure solution will meet your needs then let us know and challenge our team, we will be your low flow fluid handling specialist.

Check out our chip-sensor based mass flow meter/controllers or the Pressure Controllers using MEMS technology.

This miniaturization trend is observed in many places as can be read in our blog Customized low flow measurement systems to support winning Solution factories