Publications general

Gepubliceerd: 14 april 2019

Computer chips out of sand

Sand is very rich in the element silicon. This substance can have a very pure grid form, which gives interesting electrical properties. Such a grid consists of almost only silicon atoms. Some of these atoms can be replaced by boron or phosphorus, resulting in semiconductors or transistors in the grid.

Due to a special melting and coagulation process, the silicon atoms grow into an almost perfect grid. Solidified silicon is drawn out of a melt bath into the form of a cylinder and is cut into thin discs. These discs are called ‘wafers’ and are sold to chip manufacturers for further processing. They can make multiple chips from such a wafer, which are cut from the wafer in the end.

At present billions of transistors fit on one chip. On the basis thereof, electronic circuitry and circuit combinations are designed on the computer. These integrated circuits are printed on a 'mask', which is a glass plate with the full design of the wafer in chrome. Such a mask resembles a slide: if light shines through it you can see the image. The image on the mask must be transferred to a wafer. This is done in several steps: photolithography, etching and deposition. These techniques are too complicated to describe here in just a few words.

The above steps are not done once, but sometimes several to dozens of times. In this way, slowly but surely, all sorts of complicated 3D structures are made in and on the wafer. Metal layers are added, holes again etched, other layers added, etc. Always again with a new mask.

As a final step follows the cutting of the chips out of the wafer, after which a ceramic or plastic housing is made around it. Small wires run from the chip to pins that can connect the chip to the outside world. All these operations are carried out in a so-called cleanroom. This is necessary because the smallest dust particle will destroy the end result.

Gepubliceerd: 15 juni 2018

What can you do with a mobile phone?

What can you do with a mobile phone?
Observing organisms through a microscope can be a fascinating activity. Sometimes you want to record what you see. If you do not have a normal camera or a microscope camera at hand, then do not worry, with your mobile phone you will come a long way.
It is a bit difficult to position it well in front of the eyepiece of the microscope. But you will get used to that. See the result achieved: some images of freshwater organisms. These were taken by Ton Agterberg, member of the Dutch Society for Microscopy.

Gepubliceerd: 01 juni 2018

Sugar sweet colors

The beautiful colors we observe under the polarizing microscope have to do with the "optical activity" of - in this case - fructose.

Light is an electromagnetic wave phenomenon, in which the direction of vibration is perpendicular to the direction of propagation. An electric and a magnetic vector vibrate thereby at right angles relative to each other. In a 'normal' light, such as daylight, all directions of vibration are present at the same time. Polarized light, is light wherein only one direction of vibration in the beam is present. Polarized light is made by ‘filtering’ a light beam with a polarizing filter whereby only one single direction of vibration remains. Typically, a polarization filter is made up of two glass or plastic plates having a polarizing plastic film in between. Easily said, this film can be compared with louvered blinds. The light can only pass through it in one direction.

The polarized light microscope is designed to observe and photograph specimens that are visible primarily due to their optically anisotropic character. Image contrast arises from the interaction of plane-polarized light with a birefringent (or doubly-refracting) specimen, to produce two individual wave components that are each polarized in mutually perpendicular planes. The velocities of these components, which are termed the ordinary and the extraordinary wave fronts, are different and vary with the propagation direction and the corresponding refractive index through the specimen. This results in different wavelengths of the components. After exiting the specimen, the light components are out of phase, but are recombined with constructive and destructive interference when they pass through the analyzer, resulting in different colors. This effect can be used, for example, for the determination of minerals.

Anisotropy: A material is referred to as anisotropic when its characteristics are not the same in every direction. This concept may relate to different material properties, such as, for example, the refractive index of crystals. When the material properties do not depend on the direction, the material is referred to as isotropic.

Gepubliceerd: 14 mei 2018

Surface structures easily revealed

As it is known, revealing the surface structure of minerals and fossils can be done by making an ultra-thin section or an acetate peel. An ultra-thin section is a thin slice of a mineral or fossil mounted on a glass slide and viewed under a microscope. Preparing thin sections produces excellently detailed images, but the techniques are relatively difficult and can require expensive equipment. Making acetate peels is much easier and much cheaper.
Acetate peels are made by polishing a surface, etching it with acid to give it some relief, and then chemically melting a piece of acetate film onto that surface with the aid of acetone. The acetate film is then pulled off the surface and is examined under a microscope. In essence, the acetate film preserves a fingerprint of the structure of the surface to be studied. Other surfaces can also be examined, such as metals, botanical objects, archaeological items etc., whereby polishing and etching is not always desirable.
On the the images shown in this article, a negative imprint of a small section of the surface of a fingertip is displayed in bright- and in darkfield. The presentation of the surface details on these microscopic images can be enhanced by the application of video, based on 3D models made by photo stacking.

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Equipment for making acetate peels

Gepubliceerd: 14 maart 2018

Not just printed paper

In the Euro area national central banks together with the ECB are responsible for the printing of Euro banknotes. The ECB identifies first how many and which bills are needed. Then each central bank is instructed to press a few denominations. The ECB determines which printers in Europe are allowed to print the euro banknotes. These printers must meet the highest quality standards. The printing of Euro banknotes is a laborious process.

Like the first series of Euro banknotes the Europe banknotes are printed on pure cotton paper, which gives them their special crispness and more resistance to wear than plain paper. Certain security features, such as watermarks and security threads incorporated into the paper and often also the foil and the gold track are part of the paper itself.

If the paper is completed, the printing process can begin. Different types of plates, special inks and printing techniques are used: among others offset for the front and back side, plate print for the palpable ink, screen printing for the special color-changing ink, book printing for the serial number and hot printing for the hologram.

After printing, the sheets are cut into bills. Subsequently, the final check takes place: is the picture looking good and is there no dirt which came along? If so, the euro banknotes are ready to be issued.

It is really worth to have a look once at Euro banknotes under the microscope and to marvel at the intricate structure and the technical feat of the advanced way of paper making and printing.

Gepubliceerd: 14 december 2017

No watch without a microscope

No watch without a microscope
For years magnifiers and microscopes are needed for the manufacture and repair of watches. Who does not know the familiar image of the watchmaker wearing a magnifying glass for one eye. He is peering in stooped posture into the interior of a watch as if there is a big hidden secret inside.

It is obvious that timepieces are of extremely great importance for the functioning of many processes in society. These beautiful examples of craftsmanship must meet high quality standards. A great precision is required during manufacture. There the microscope comes into play. The user should be able to count on an accurate and durable indication of time.

It is clear that the above is only possible thanks to the existence of, amongst others, excellent optical equipment. In the picture a part of an old Russian pocket watch is shown. It is a curiosity from the beginning of the seventies of the last century.

Gepubliceerd: 01 december 2016

Just stones?

Tumbled stones are small pieces of rocks and minerals (usually about one to five centimeters in diameter) that have been processed in a rock tumbler to produce smooth, rounded and highly polished pebbles. Most stones that a person can find will not tumble with good results. The rocks and minerals used to make tumbled stones are specially selected for their color, translucence, appearance and ability to accept a high polish. These special materials are known as "tumbling rough". Some people collect their own tumbler rough and some buy it from a hobby supply store. Tumbled stones are often so beautiful that many people call them “tumbled gemstones.”

Tumbled gemstones are used to make jewelry, craft projects and other decorative items. They are also widely collected by people who appreciate their beauty and have always been associated with spiritual and healing properties by some superstitious people. They are especially enjoyed by children. Tumbled gemstones are extremely popular in gift shops – especially gift shops found at science centers, caverns and other natural science attraction s. Many geologists obtained their first interest in rocks and minerals when they received tumbled stones as a gift or discovered them in a store.

Gepubliceerd: 29 juni 2016

Art, design and crystals

Art, design and crystals
In her studio in the Port of Rotterdam the innovative artist and designer Liesbeth Bulk is experimenting with the growing of crystals on everyday and design objects. She tries to combine the beauty of crystals with the structure of objects. Mastering this artistic and technical challenge is still at an initial stage. Until now, trials have been carried out with sugar crystals. When we look at the picture taken with a Motic stereo microscope, it is not surprising that artists are fascinated by the beauty of crystals and start experimenting with them, as can be seen on the image below, showing a small part of Liesbeth’s art lab.

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Liesbeth is a designer with a fascination for nature, she also creates bespoke glass panels with enclosed natural elements. With profound knowledge of plants, the flowers, leaves and twigs are collected in the wild. Searching for a way to merge the lush plants with monumental, architectural characteristics, she started experimenting with the forgotten technique: pressed flowers.
Liesbeth Bulk (1968) studied garden design at the Horticultural college in Boskoop, The Netherlands. In 1998 she completed her studies at the Sandberg Institute (post academic course at the Gerrit Rietveld Academy Amsterdam) with a masters in fine arts. For examples of her work use the links below.
Source: www.crush-on-nature.nl and http://www.liesbethbulk.nl

Gepubliceerd: 01 april 2016

Wool, too tight for comfort?

Wool has been a precious raw material for people for a long time. Yarns have been spun out of wool fibres for several millenniums. As the range of available fibres was limited in the past, wool used to be a very valuable commodity. Today we are able to select between a huge variety of fibres with varying properties, but nevertheless, the percentage of wool in fibre production all over the world averages out to a few percent.

The continuing use of wool – in spite of the competition with other natural fibres and new synthetic fibres – for suits, coats and pullovers can be attributed to the unique properties of wool:
- thermal regulative due to high amounts of air embedded in the fibre
- high absorption of moisture
- low tendency to creasing
- low flammability

However, wool has not just got properties which offer high wearing comfort. A big disadvantage, which emerges during washing, is the felting tendency. Under the influence of warm, alkaline water, the scales surrounding the wool fibres rise. If the wool fibres are additionally moved, the fibres wedge with each other more and more since they can only glide in one direction due to the scales. The fabric shrinks and gets tighter.

To prevent felting of wool and to make wool washable in normal household washing machines, several methods have been developed:
- softening/removing of scales by chemical modifications (oxidation)
- covering of scales by application of a resin
- combination of oxidation and enzymes
- plasma treatment
- combination of removal and covering (so called Chlor-Hercosett-process)
- Petry-anazym-proces

Gepubliceerd: 01 december 2015

Urea, a chemical indispensable for life

Urea is an organic compound with the chemical formula CO(NH2)2. The molecule has two NH2 groups joined by a carbonyl (C=O) functional group. Urea serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals. It is a colourless, odourless solid, highly soluble in water and practically non-toxic. The body uses it in many processes, the most notable one being nitrogen excretion. The average person excretes about 30 grams of urea a day, mostly through urine, but a small amount is also secreted in perspiration.

Synthetic versions of the chemical compound can be created in liquid or solid form. Urea is widely used in fertilizers as a convenient and indispensable source of nitrogen. Urea is also an important raw material for the chemical industry. It is used to produce some types of plastics, animal feed, glues, toilet bowl cleaners, dish washing machine detergents, hair colouring products, pesticides, and fungicides. Medicinally, it is used in barbiturates, dermatological products that re-hydrate the skin, and diuretics.

Gepubliceerd: 01 augustus 2015

Multipurpose polyester

Polyester is an umbrella term that describes a manufactured fiber whose substance is any long-chain synthetic polymer, where at least 85 percent (by weight) of the polymer is an ester and terephthalic acid. Most polyester is made of polyethylene terephtalate. The properties of polyester fabrics vary depending on their composition, web structure and processing, but some general features are found with nearly all polyester fabrics.

Polyester is a strong and durable synthetic fabric. Polyester dries quickly and can be washable or dry clean only. Polyester is often used as a blend with other fabrics to lend wrinkle resistance. It is not the easiest fabric to remove stains from, and doesn't breathe as well as other fabrics may.

Fabrics woven or knitted from polyester thread or yarn are used extensively in apparel and home furnishings, from shirts and pants to jackets and hats, bed sheets, blankets, upholstered furniture and computer mouse mats. Industrial polyester fibers, yarns and ropes are used in tire reinforcements, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements with high-energy absorption.

Sources: Ehow, Wikipedia

Gepubliceerd: 25 april 2015

Crystal clear and colorful

Crystal structure of Phenyl-2-hydroxybenzoate or phenyl salicylate, or salol, is presented here by using polarization microscopy. It is a chemical substance, introduced in 1886 by Marceli Nencki of Basel. It can be created by heating salicylic acid with phenol. It appears in the form of small white crystals or crystalline powder with pleasant aromatic odour and taste. Once used in sunscreens, phenyl salicylate is now used in the manufacture of some polymers, lacquers, adhesives, waxes and polishes. It has been used as an antiseptic based on the antibacterial activity upon hydrolysis in the small intestine. It acts as a mild analgesic.