Question of the Week

Feb 282018
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Conjoined twinning is one of the most fascinating and at the same time devastating human malformations. This is an extremely rare phenomenon. The occurrence is estimated to range from 1 in 50,000 births to 1 in 100,000 births [1], when identical twins are born physically connected to each other. They can be joined anywhere—head, chest, abdomen, hips, and so on [2]. In fact, there is a whole spectrum of cases with different degrees of bodily overlapping: from being joined by a thin sliver of skin to being extensively fused. The “fusion” can be so extensive that in some cases, it is no longer correct to talk about “twins” because there is only one individual with some extra organs [3].

Conjoined twins have been known to exist for centuries, yet there is very little understanding of this phenomenon. Common public questions are: How do conjoined twins live together? How do they eat, walk or manage any other daily routine activities? Do they share thoughts and can they read each other’s mind?

The answers to these questions are indeed different for different pairs of conjoined twins. For example, 27-year old Abigail “Abby” and Brittany Hensel are joined at the torso. They have two hearts, two spines, two sets of lungs, two arms and two stomachs. Below the waist, they are more like one body. Each twin controls her half of their body – Brittany, the left twin, can’t feel the right side of her body, and vice versa. Each twin manipulates one arm and one leg.

As infants, the initial learning of physical processes that required bodily coordination, such as clapping, crawling, and walking, required the cooperation of both twins, even standing up takes total coordination. Now as grown-ups they are incredibly well coordinated with this set-up, able to walk with a smooth gait, dribble a basketball, ride a bike, and even drive a car: both steer and Abigail controls the accelerator with her right foot. The really mesmerizing thing is watching them type on a computer, as both girls’ hands fly over the keys, but there is no verbal discussion of what they are writing [4].

For 98 percent of all sets of conjoined twins, each person has their own separate and distinct thoughts and feelings. But in the case of Tatjana and Krista Hogan [5], which occurs in only one in 2.5 million births, they share neural activity because their skulls are connected.

The girls are still too young to investigate their neurological wiring, but from the MRI scans, doctors have determined that there is a “thalamic bridge” that links one sister’s sensory input to the other, creating a conscious loop. Essentially, if one thinks a happy thought, the other can perceive it. When one sees an image through her eyes, the other receives the image milliseconds later.

With a few tens pairs of conjoined twins across the world today Abby and Brittany, Krista and Tatjana are defying the odds. And a fair answer to all the curious questions can be that they are able to do normal things, even though it takes a lot more effort for them than anyone can imagine.


— Mariia Filianina

  1. Mutchinick, O.M. Conjoined twins: a worldwide collaborative epidemiological study of the international clearinghouse for birth defects surveillance and research, Am J Med Genet C Semin Med Genet. 0, 274 (2011).
  2. Kaufman, M.H. The embryology of conjoined twins, Child’s Nervous System 20, 508 (2004).
  3. Savulescu, J. and Persson, I. Conjoined twins: philosophical problems and ethical challenges, Medicine and Philosophy 41, 41 (2016).
  4. Abby and Brittany: Joined for Life, BBC.
  5. Ryan, D. Through her sister’s eyes: conjoined twins Tatiana and Krista were extraordinary from the beginning. The Vancouver Sun[On-line] (2012). Available:


Jan 082018
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Is Mycelium the Material of the Future?

No, mycelium is not a recently discovered chemical element. It might be the solution to the question of how to replace petroleum-based materials!

Mycelium is the tenuous web of vegetative fungal cells called hyphae that grows in the soilas shown in figure 1.[1] The parts of fungi that we usually see are just their body fruits (mushrooms, chanterelles, shiitake,…). But mycelium forms a much larger network below the surface that can even spread over several thousand square kilometers.[2] It is one of earth’s most important organisms since it helps nature to “digest”, meaning that it decomposes organic material and turns it into compost.[1]

Figure 1: Microscopic image of a mycelium network (size 1 mm · 1 mm).[3]

But can this bio-based material save our planet? The answer to this question could be easier as you might think. Fungal material is renewable, compostable under certain conditions (moisture and the presence of other organisms), fire resistant, moldable, free from volatile organic compounds (VOCs), dyeable and vegan.[4]

Companies like Ecovative and MycoWorks have already started to produce items from mycelium that can find access to our daily life.[4,5]

Ecovative was founded in 2007 and claims to produce more than 450,000 kg of mycelium material per year. They explain the production process on their webpage:

Agricultural waste is seeded with mycelium from mushrooms like Ganoderma. After some time of incubation, the waste is cut into little particles that are filled into a mold with the desired shape. The mycelium grows a few days until it has filled the mold and can be removed. In a last step the solid material is dried to stop the mycelium from growing. From that process packing material and even decoration can be made.[6] Imagine how many things could be substituted that are still petroleum-based and not compostable.

MycoWorks, founded in 2013, is specializing on replacing leather by mycelium – a relieve for our vegan friends. They claim that “…it feels and performs like leather”.[5] Indeed, recently I had the chance to touch a sample of “mycelium leather” and it does feel quite comfortable!

Mycelium as a full substitute for most of our plastic-based everyday products has still a long way to go. Sure, fugus as fancy packing material is not unusual anymore but customers still have to be convinced to wear clothes made from mushrooms. After all, some fungi are responsible for decay and mould. How will it react on the (moist) skin? Can it be washed without any damage to the fabric? How quickly does it decompose?

There must still be made a lot more research and explanatory work until consumers are convinced to take mycelium as an impeccable material. But maybe one day the world will be greener and we will be producing less eternal waste.

– Tatjana Daenzer

Read more:

[1], last access: 15.12.2017, 15:33.

[2] Ingraham, John L.: March of the Microbes: Sighting the Unseen, Harvard University Press, Cambridge 2010.

[3] CC BY-SA 3.0, last access 15.12.2017, 16:52.

[4], last access 15.12.2017, 15:58.

[5], last access 15.12.2017, 16:26.

[6], last access 15.12.2017, 16:09.

Dec 032017
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How will the IT technology develop within the next decade?

Firstly, the term itself refers to the nowadays common praxis to “outsource IT activities to one or more third parties that have rich pools of resources to meet organization needs easily and efficiently” [1, 2]. In other words, one buys the permission to use hardware, network connectivity, storage, and software that is located in a computing center anywhere in the world. It is more or less comparable to other known public utilities such as electricity, water and natural gas [1] and follows the same rule: You pay for what you need, not more.

The private sector is also more and more part of the system. Cloud memory saves personal data and makes it available from any place with an internet connection, file sharing websites are widely used and gained a lot of popularity within the last years. Another kind of cloud computing is especially interesting for research: Branches with high computational needs, e.g. astrophysics, medicine, and large scale facilities like CERN, can save a lot of resources by outsourcing computational power to volunteers. While their PCs are idle, a program starts in the background and performs calculations for the project [3].

The current state of cloud computing is already very impressive, however there is one major goal the IT industry starts to tackle now, namely the so-called Internet of Things (IoT). An example is Near Field Communication (NFC), a set of hardware and software protocols to enable two devices to communicate wireless with each other [4]. It is already part of most modern smartphones and also widely used for contactless payment cards. More and more devices in our daily life will be included in this IoT, resulting in increased connectivity and data flow around us. The idea is to take the cloud and place it everywhere around us, basically creating a fog [5]. This now indeed called “fog-computing” could span a wide range of applications in daily life. From smart houses that adjust the temperature, to refrigerators that tell their user when they are getting empty. An even more spectacular application could be connected to the trend towards self-driving cars. Large IT companies already started to develop cars which do not need a driver any more [6]. What sounds like science fiction could become commonly available within the next decades and opens the path to some great applications of fog-computing. How about a traffic light, which already counts the arriving cars and adjusts its phases according to the traffic volume or tries to prevent accidents by detecting obstacles and pedestrians much faster than any human would be able to? The possibilities are incredible.

However, one also needs to consider possible disadvantages like data safety and the problem of the totally transparent citizen. Moreover, judiciary will require a lot of adjustments and new laws, especially when the computer hardware that processes cloud data is located in another country with different data protection laws. There are a lot of changes to be made, however so far technological progress was never stoppable. We will most likely be able to observe within the next 10 years some of the biggest changes in IT technology and connectivity since the invention of the internet itself.

–Kai Litzius

[1] Hassan, Qusay (2011). “Demystifying Cloud Computing” (PDF). The Journal of Defense Software Engineering (CrossTalk) 2011 (Jan/Feb): 16–21.}
[2] M. Armbrust, A. Fox, R. Griffith, A. D. Joseph, R. Katz, A. Konwinski, G. Lee, D. Patterson, A. Rabkin, I. Stoica, M. Zaharia, “Above the Clouds: A Berkeley View of Cloud Computing”. University of California, Berkeley, Feb 2009.
[4] Cameron Faulkner. ” NFC? Everything you need to know”.
[5] Bar-Magen Numhauser, Jonathan (2013). Fog Computing introduction to a New Cloud Evolution. Escrituras silenciadas: paisaje como historiograf?a. Spain: University of Alcala. pp. 111–126.
[§] Google Self-Driving Car Project Monthly Report – September 2015″ (PDF). Google.

Nov 162017
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Figure 1. Scaling effect of global maps. The circles would all have the same size on the Earth’s surface. [1] Copyright: BY-SA 2.5 (Eric Gaba)

If we think about an earth map, gigantic Asia, Antarctic and North America with Greenland comes up in our mind. However, have you ever thought more about our self-created 2D maps of the earth? Do those maps represent the real sizes of our countries? Are Antarctica and Greenland as big as they seem and Africa in comparison to other continents so small. The answer for most of the 2D maps we are looking at is No! The most maps do not show the true sizes of the countries, because the countries of our round planet were just planed to a 2D paper without the correct scales. Meaning the continents or countries closer to the poles look a lot bigger as they are whereas the ones close to the equator look a lot smaller (see Fig. 1).

How did this happen? Our maps are older as we think. A Belgian geographer and cartographer Gerhard Mercator from 1569 designed those maps we are still looking at. This model is convenient for the seafaring, because you need equatorial azimuthal projections for navigation. In terms of ratios of the countries, the model is indeed sometimes wrong. It does show Greenland and Antarctica totally stretched and therefore bigger as they are. For example, Africa is 14 times larger than Greenland in reality. Madagascar is actually bigger as the United kingdom. Where Ireland also is 3 times smaller than it seems to be on a map of Mercator (see Fig. 2).


Figure 2. Direct comparison of different regions

There are several approaches now on shedding some light on this fact. One webpage showing the optical illusions is called “true size” [4]. Here you can move countries to another region of the earth and their scale will be dynamically adjusted dependent on the local distortion of the map. Another example is given here with a map built using the Cahill–Keyes projection (first proposed by Cahill and refined by Keyes in 1975). In this ensemble, the map provides an easy understanding of the continents with a minimized distortion (Fig. 3). Of course, another possibility to have a quite precise image of our world is to have a globe if you have enough room to have it.

Figure 3. Political world map for 2013 CE using the Cahill-Keyes Projection. Copyright: Duncan Webb CC BY 1.0


— Dania Rose-Sperling

Aug 142017
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Sometimes they come and go with a bang, sometimes they are silent. They glow bright as a lightning in white, yellow, red or blue. They fly freely through the room and some of them even permeate solid matter. They all have in common that they appear mostly during stormy weather, are somewhat spherically shaped and have a lifetime of several seconds.[1] For many centuries people report about observations of lightning balls as depicted in figure 1.

Figure 1: Illustration of a ball lightning from the early 20th century.[2]

Clearly, ball lightnings cannot be the same phenomenon as a strong electric discharge like a bolt lightning since their effect is not as dramatic. A full scientific explanation is not yet found. Do they really exist or are they only the product of frightened people’s minds?

Sure, bolts can cause phosphenes, impressions in the focus of the eye that remain some moments after looking into bright lights.[3] But during the last years scientist came up with some experiments that deliver plausible explanations of their formation:

Abrahamson and J. Dinniss found out that after the impact of a bolt into the soil a cloud of Silicon (Si), Silicon carbide (SiC) and Silicon monoxide (SiO) nanoparticles evaporates and oxidizes in a timespan of several seconds. During this time the energy is released as a bright ball-shaped light.[4]

At the IPP in Garching, Germany, Prof. Dr. Gerd Fu?mann vaporized and ionized a tiny amount of water by an electrical discharge between two electrodes above a water surface. The glowing plasma cloud, called plasmoid, has a spherical or mushroom-like shape (shown in figure 2) and a lifetime below one second.[5] The appearance of these plasmoids is demonstrated in a short video on their web page:

Figure 2: Result of the water discharge experiment from 2014.[6]

Still these experiments lack to explain all the observed properties of a ball lightning: the free movement, the ability to permeate matter and the long lifetime of several seconds. It is plausible that there might occur spherical light phenomena during bolt impacts. An explanation of the rather vivid properties of a ball lightning is yet to come. But maybe they belong to the section of narrative decor.

– Tatjana Daenzer

Read more:

[1] Smirnov, B. M., Phys. Rep. 1987, 152, 177-226.


[3] Peer, J., Kendl, A., Physics Letters A, 2010, 374, 4797-4799.

[4] Abrahamson, J., Dinniss, J., Nature, 2000, 403, 519-521.

[5] Fussmann, G., Phys. Unserer Zeit. 2008, 5, 246-252.



Jul 242017
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Put a raw egg on a flat table, and give it a good spin with two fingers. The egg spins, however, rather slowly because the liquid inside poorly exchanges momentum with the outside shell. Thus, when you spin the egg by applying force to the shell, most of the inside resists the motion and the friction forces between the inside (immobile) and the shell (mobile) will be slowing down the egg’s speed. But if you consider a cooked egg, proteins contained inside the egg are now forming a solid phase that is tightly joint to the shell. In that case, there are no friction forces in the “egg system” and the movement is not slowed down.


In this case now, the only existing friction forces are those between egg and the support (the table) and the air (which can be reasonably neglected). If your initial momentum transfer is strong enough, you observe a strange phenomenon: the spinning egg starts to rotate upright.

The physical concept used to explain this phenomenon is inertia. Spinning ice skaters can reduce their moment of inertia by pulling in their arms, allowing them to spin faster. You can also sit on a swivel chair and spin on yourself. Extend your arms horizontally and you will slow down.  The same is happening with the egg. Friction forces tend to slow down the egg, and decrease overall energy. To save energy, like the skater, the egg stands up and the momentum of inertia consequently decreases.

To spin upright, the egg needs some energy, exactly as one needs some energy to get up in the morning, fighting against gravity. The necessary energy is provided by the rotation itself, and the change of orientation of the egg will only happen if the spinning is fast enough.




Video movement of interia

Bou-Rabee, N. M., J. E. Marsden, and L. N. Romero, A geometric treatment of Jellett’s egg, Angew. Math. Mech. (ZAMM) 85, (2005), 618-642

Jul 102017
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Ordinary glass as it is used for windows can exhibit exceptional behaviors and even shred a rifle bullet to pieces, furthermore it can help to make car windows safer and to understand the inner processes in volcanos.

Key to all these fascinating properties are the so-called Prince Rupert’s Drops. These structures are solidified drops of glass, which are produced by letting a drop of molten glass fall into a bucket of water. The sudden shock caused by the massive temperature drop on the surface of the glass basically locks in the outer shape of the drop, preserving main body and tail. (Fig. 1) [1,2,3].

Fig. 1: Prince Rupert’s Drops. The thick main body with the long, thin tail is well visible (Copyright: public domain). [1]

This object has now very unique properties: If the main body of the droplet is hit by a hammer, it practically never breaks. It even withstands a direct hit of a rifle bullet, whereas the bullet can be completely shred to pieces. All this the main body of the glass droplet can stand without breaking. However, if there is too much force applied to the fragile tail of the Prince Rupert’s Drop, or if it is even just nicked, the whole drop explodes into tiny pieces of glass that can spread over several meters. [4,5]

To understand how this fascinating behavior is created, we have to have a closer look at how the drop is created. Everything starts with a drop of hot, molten glass, suddenly getting in contact with water. As mentioned, the outer layer of the drop immediately solidifies and locks in the characteristic drop or tear shape. The thin tail is created when the drop detaches from its origin (e.g. the glass rod) and starts falling and also gets locked into its shape when touching the water for the first time. While the outer layers are now already solid glass, the interior of the drop is still a hot liquid (Fig. 2 top). Consequently, this glass contracts while cooling down and starts pulling the solid outer layers inward, stressing them just like an arch bridge is stressed (compressive strain) and thereby stabilizes the structure. Along the axis of the drop, however, the strain is not compressive but tensile, because the shrinking material tries to pull along the tail.

Fig.2: Mechanism of creation of a Prince Rupert’s Drop. The hot, liquid interior of the drop compresses against the already hardened outer shell. The result is a highly strained structure (Copyright: CC-BY JUnQ). [4,5]

These stresses make the round shaped main body of the drop extremely resistant to external disruptions, whereas the tail constitutes a weak spot (Fig. 2 bottom). If the latter is now damaged in any way, the energy stored in the mechanical stress can be released and a mechanical failure front runs through the material, destroying more and more of it until the main body is shredded into dust. This process can happen with a speed of around 1600m/s, just like an explosion, and it usually only ends with the pulverization of the whole drop. Thus, this is the secret of the Prince Rupert’s Drop; it is always experiencing extreme internal stress that makes the convex part so extremely stable (like an arch bridge) that even rifle bullets shatter on them.

Finally, in its cooled state, the drop represents a system that exhibits extreme internal stresses. These stresses make the round shaped main body of the drop extremely resistant to external disruptions, whereas the tail constitutes a weak spot (Fig. 2 bottom). If the latter is now damaged in any way, the energy stored in the mechanical stress can be released and a mechanical failure front runs through the material, destroying more and more of it until the main body is shred to dust. This process can happen with a speed of around 1600m/s, just like an explosion, and it usually only ends with the pulverization of the whole drop. Thus, this is the secret of the Prince Rupert’s Drop; it is always experiencing extreme internal stress that makes the convex part so extremely stable (like an arch bridge) that even rifle bullets shatter on them.

So, we can ask whether this effect can be useful for anything. The answer is yes, indeed. Exactly the same principle is used in tempered glass like it is used e.g. in car windows. This glass does not shatter into sharp shards, but instead produces relatively smooth and small pieces and therefore is less harmful for the passengers of the car in case of an accident. Currently, Prince Robert’s Drops are even researched to understand better the quick cooling of volcanic lava under certain circumstances and therefore the inner processes within a volcano. Thus, all in all, these fascinating objects are full of wonders.

— Kai Litzius

Jan 162017
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Have you ever wondered why rubbing alcohol, i.e. isopropyl alcohol, which is used to disinfect cuts burns so much when applied to the wound? As my mother always said: “As long as it burns, it helps”. This didn’t help me much as a kid, anyway. But why does it burn in the first place? Do you feel the bacteria die? Do some of your cells get killed, too, and you feel that?

Feel the burn.

Feel the burn.

In fact, neither is true. Interestingly, the pain you feel is due to a heat reaction. But wait, doesn’t alcohol usually give you a cool sensation when applied to the skin? True, but when the alcohol is able to penetrate your skin, e.g. when you have a cut, it gets in contact with your vanilloid receptors-1 (VR1). These are heat-gated receptors that normally get activated when the temperature rises above 42 °C, sending a painful sensation to prevent tissue damage by overheating. But why do your VR1 send a pain signal, even though the temperature does not rise above 42 °C? A study, a few years back, showed that alcohol has a similar effect on VR1 as capsaicin, the substance from chilies responsible for the hot taste.[1] Alcohol and capsaicin “trick” the VR1 by lowering the switch temperature from the above mentioned 42 °C to roughly 34 °C. Accordingly, your body temperature is high enough to induce an alert signal of VR1, giving you a burning (heat) pain even though your tissue isn’t nearly hot enough.

Maybe it helps you in the future when disinfecting wounds (or eating hot food) when you think that the pain is not real but rather a trick by played due to your heat receptors.

–Andreas Neidlinger

[1] M. Trevisani, D. Smart, M. J. Gunthorpe, M. Tognetto, M. Barbieri, B. Campi, S. Amadesi, J. Gray, J. C. Jerman, S. J. Brough, D. Owen, G. D. Smith, A. D. Randall, S. Harrison, A. Bianchi, J. B. Davis, P. Geppetti, Nat. Neurosci. 2002, 5, 546-551.

Jan 082017
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According to media reports, the Italian neurosurgeon Dr. Sergio Canavero will attempt the first transplant of a human head (cephalosomatic anastomosis) in the end of 2017.[1] Valery Spiridonow is volunteering for this project since he suffers from spinal muscular atrophy (SMA) and believes the surgery will offer a chance to escape from this fatal disease.[2]

Similar experiments have already been performed more or less successfully on animals. In some cases, the animals survived but they remained paraplegic and their cardiovascular and respiratory systems had to be supported. Also they did not survive quite long after the surgery.[3,4] In fact, many experts are strongly doubting the success of this highly expensive transplant too.

Head Transplant : Fact or Fiction ?

Head Transplant : Fact or Fiction ?

Even if it might become a 100 % success, there remain a lot of serious questions:
– Will the patient (the head) be mentally and emotionally the same person as before?
– Will the brain be able to cope with a completely strange body and vice-versa?

Of course, Spiridonow will first have to find a donor for the body. He needs the body of a physically healthy man suffering from cerebral death and the consent of his relatives. Spiridonow’s new body will have the genome of the donor, so what are the legal consequences for any offspring regardless of whether they were conceived before or after the transplant?

So once again we are confronted with the problem of how far mankind can go to explore the possibilities of science and consider ethics at the same time. I think we should be excited and enthusiastic for the outcome of this dramatic surgery if it is going to happen anyway.

— Tatjana Daenzer

Read more:
[3] Canavero, Surg Neurol Int. 2013, 4, 335.
[4] Canavero, Surg Neurol Int. 2015, 6, 18.

Nov 162016
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Touchscreens are getting more and more important for modern media. The most striking advantage of this technology is the combination of intuitive in- and out-put devices, which allow the user to directly interact with the system and vice-versa. But how does such a screen work, which types are available, and why do certain type of touchscreens react to fingers, but not to a normal pen? These questions we will answer in this week’s featured question.

How a resistive screen works?

How a resistive screen works?

One of the first touchscreen technologies (that is still in use nowadays) is the so-called resistive screen. This specific screen type is composed of two conductive, relatively transparent layers (usually indium-tin-oxide (ITO)), which are held separated at a small distance by spacer dots. To the bottom layer, a small voltage is alternatingly applied in x- and y-direction, while the top layer connects to the second half of the circuit. They are capped by a stiff, but bendable layer and directly sit on the actual display. Touching the screen with a little bit of pressure bends the conductive layer on top and closes the circuit. The resulting currents along the x- and y-circuits can be measured and provide information about where the circuits are closed. The idea is that the longer the current path , the higher becomes the electrical resistance. This technology is still commonly found in cheaper devices and in devices meant to be operated with gloves and can yield high accuracy. However, due to the mechanical deformation the screen has a finite lifetime.

How a capacitive screen works?

How a capacitive screen works?

The second, and probably most common, technology is used in “projected capacitive screens”. Those screens are composed of two grids, rotated at 90° to each other, of very fine conductive wires (usually ITO deposited on glass) with spacers in between. In contrast to the resistive screens, they do not form a continuous layer. Instead, the ITO grids create a large amount of crossings, which act like little capacitors whose capacity changes whenever a conductive or dielectric object (like a finger) approaches the grid. A digital controller measures now the capacity of all grid points one by one and if a certain deviation from the saved standard value is reached, a touch is registered. This technology allows multi-touch applications since all grid-points are measured separately and the image quality is enhanced due to the lower amount of ITO between the user’s eye and the actual display. However, these touchscreens need specific materials to be able to detect a signal and barely work with thick gloves or normal pens due to the fact that the capacity does not change if a standard insulator (like plastic) is brought close to it.

There are far more types of touchscreens based on, e.g. infrared light, inductive coils, sound and the piezoelectric effect. However, the two types, mentioned here, are the most commonly found ones nowadays. In the future, there might exist even more sophisticated types of human-interface-devices (HIDs), but at the current time, touchscreens still are one of the most successful HIDs and were able to widely repress the simple push-buttons.

–Kai Litzius

Further reading: