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What makes some materials like cat fur or velvet feel soft?

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1.0k points · 4 months ago

Long time lurker but finally a question I can answer. (Source: am materials scientist who works on softness in industry).

Softness is a complex, multi-variable phenomena which we think involves two components: 1) the material a person touches and 2) the persons [somatosensory system] (, which is a combination of the nerves in your finger and neural system. Since the brains involved, things start to get complex.

Like the other commenters have mentioned, a simple reason for observing why a piece of cat hair is soft is linked to the fiber diameter. In fact, research has shown that a small fiber diameter of a material class does link to a greater degree of softness . But pet your cat in one direction (toward the tail) and a different direction (away from the tail), and you might have a different experience. What this means is that by orienting the fibers in a different ways, you're body can register a difference sense of softness.

Taking it on step further, the micro and mezo-structures of the fiber also (things like kink, curl, or shape) play a part. Surface coatings, and blooming agents are readily sought in the synthetic fiber making world to enable softness at the fiber level. All different type of animal (and people for that matter) have different natural hairs which kink, lay straight or flat depending upon the way the hair is formed.

The macro structure of a fabric or group of hair matters too as there is active research ongoing to characterize the behavior of fabrics and other composite materials like velvet. You can get into macro level properties like drape, compressive modulus, friction, and even the sound of fabric or hair, to get into a response that could be considered soft.

The other aspect (which I don't have good sources for other than data I've generated) is that what you put behind a material matters immensely. If you put your cat hair on top of brick, you are likely to not think its so soft versus against the cat's skin, since the skin bends easily. An analogy would be, take a piece of velvet and wrap it around a brick. That velvet brick will likely feel soft to the touch if you barely put pressure on the top of the fabric, but put a little more pressure, and it doesn't feel so great.

The reason I put "we think" at the top is because unfortunately the instruments used to measure softness are humans, so the variability in the data is very high. In fact, not having an "anchor" in a softness assessment almost always provides data that isn't repeatable from test to test (i.e. feather = 1, brick = 10). Further more, since the somatosensory system involves your brain, things like sounds, color, what you ate, how you feel that day, can skew data. We can find general trends in the data which point toward some general characteristics for softness directions (small smooth fibers, in a highly drapable and cushiony fabric), but within material groups, differences are hard to find.

Lastly, the aspect that really makes things difficult, and I find fascinating, is that across cultures, softness perception changes. I have seen two study groups from Japan/China and the US have completely opposite opinions of what "cottony" means. Even using a material that is considered soft in one culture, doesn't work in another because of how softness is defined in each.

TL;DR : It depends.

That TL;DR though.

With the cultural perception being different, isn't it that they have different meanings behind the words, not that the tactile sense (?) of identical soft sample is physically perceived differently? Or do different cultures rate an identical sample differently? (for instance an average of 6/10 instead of a 4/10)

Some put more emphasis on low friction and low density in their personal understanding of softness, while others would put more focus on tactility and how much feedback the material gives. Particularly for pillows and duvets; how much weight they can carry is a measurement of softness used in the industry, where a higher weight is normally better

I like this answer a lot. I think its really focused on the feeling of something like fur itself. I also agree completely that it depends of a huge number of factors, and a lot of our preconceived notions we bring to perception before we even touch something.

When it comes to more surface like structures (not hair, fur, etc) I think we are starting to get more objective answers on what sensations people can pickup and percieve on their fingers. The problem is, however, that we don't have a great shared language to talk about it so, as you say, "cottony" has no shared meaning. We need something that is objective "softness" in the same way "blue" is a (somewhat) objective description of a visual color!

2 points · 4 months ago

This is a big problem. There was a paper a few years ago that looked at vibrotactile sensation (they used exact frequencies and chords instead of texture, but it's the same process of sensation). They used conconant and dissonant stimuli and allowed subjects to describe the sensation with any adjective. While "pleasant" and "unpleasant" were on the list of common responses, my favorite are "divine" and "blasphemous" and "muddy".

Could you elaborate on the cultural bit?

Are you saying that what we learn to call soft growing up affects what we actually feel in softness? What are the differences?

11 points · 4 months ago

Commented above a bit on this but I'll expand a bit further because it fascinates me. Within the fabric industry, there is a device which characterizes the overall mechanical performance of a fabric or structure called the Kawabata Evaluation System. You output a set of mechanical constants for each material which tells you... something. That material is more plyable to others, etc. Work been done to connect the KES values into a multi-variate equation for softness. So great, each material deforms and behaves differently. In that sense, its possible to create materials or fur with the best bending, compression and strength properties ever.

A human will respond to each of those properties and measure them, themselves. The issue is, how you prompt the consumer differently or they inherently weight the importance of those measures differently from region to region. So no one has yet to truly, objectively validate the mechanical measurements to the human response, and repeat that data over and over again. We (the royal we), just say "o thats soft". Add in the effects of layers, and the equation gets more complex, or the fact that the device measures a limited amount of variables (heat transfer, sound, light scattering not included)

So is it something you grow up with? I'm not the person to answer that but I have seen the same materials with the same mechanical description get rated differently. I'd guess that our biomechanical responses across cultures to stimuli vary based on upbringing, and previous experiences.

2 points · 4 months ago

That's interesting, there is a lot of research on how culture affects how we experience pain. There's the common parenting trick of not acting worried when a child falls, I imagine that affects what threshold of pain they can take over time. Or your culture's view on healthcare, again, I would think that having to tough out certain sicknesses also leads to a higher pain tolerance. An accumulation of these behaviors can have significant differences between cultures on how they experience the same action. I wouldn't have thought it affected perception of softness, but it makes sense.

Thank you for your explanations, very interesting.

That makes a lot of sense. Thank you for such a detailed answer!

Any ideas why particular softnesses can be perceived adversely? I'm a pretty tactile person and flock to things that are soft, but the feel of velvet and corduroy really really gross me out. The more plush the velvet, the worst it is. My immediate response is to cringe and rub my affected body part vigorously on something else like my jeans if it's my hand. It leaves a negative impression for a solid few minutes.

This! I have similar adverse responses to things like cotton balls and chalk. I love soft things, and fur does not bother me in the slightest. But the thought of having chalk under my fingernails literally makes me want to pass out. I've never been able to find a reason for this., would love to know why!

Thank you for the great explanation.

Also, petting your cat in the wrong direction will result in severe, burning scratches.

Hey, I'm a MatSE major, what can I do to get an internship?

Cat hair feels different when rubbed the other way mostly because you're bending the hairs and adding additional tension/textures, plus the way hair grows you're likely to run into friction due to the cuticles. You say the brain can differentiate between the two like it's some miracle, but it's because the hair is a different shape... not because your brain reads it backwards like a credit card strip lol.

Is surface coatings why my polyester shirts start our as the softest thing I own then become scratchy monstrosities?

2 points · 4 months ago

Could be one explanation. You'd need to look at your shirt under a microscope to understand the mechansim for why it feels like a monstrosity.

More likely, though, the material is being damaged via normal wear. The individual strands in the fiber are fraying (fabric softeners help here) or the fiber itself is coming out of the weave (patching helps here). Take a look under a microscope and see!

PET as a fiber can be smooth, depending on the process conditions used. Most typically, its strained so much that it crystallizes rapidly into a highly aligned and crystalline structure. That makes it seriously strong and easy to see through. You can also not strain the fiber, and yield an amorphous microstructure, which is weaker, more opaque but thicker. Surface coatings can be used to change things like surface energy, index of refraction and friction, and the research is most focused on permanent modifcations that don't wash off. All of this is what material science is all about!

They don’t use dryers in china. They hang dry. So cotton remains stiff and hard and scratchy. Even high quality cotton is just not soft there because they hang dry and don’t use a dryer with a dryer sheet to fluff and buff a shirt or outfit.

Could you devise something like a Moh's hardness scale but for softness? Could be repeatable if you guide test subjects I.e. if you just say "rate on a scale of 1 to 10" you will get widely varying answers but if you give them a guide it would at least make your data more controlled.

Like 1 = jello, 3 = feather, 6 = tire, 9 = brick

Or have a bunch of differently soft and textured objects for them to compare to.

Or does something like this already exist? Or would it invalidate the data?

People tell me that velvet is supposed to feel soft, but I hate touching it. I feel every stiff fiber and it makes me bristle. How can I have such a completely different experience than everyone else?

963 points · 4 months ago · edited 4 months ago

I would agree with funintheburbs comment, but add that it is not just the 'give' of the material as a whole that gives it that velvety feeling (for example, a sheet of cotton has a lot of give, but does not produce the same feeling as cat fur), but also the diameter and density of the fibers comprising the surface of that material. A material with a high density of narrow, flexible fibers will feel soft, like fur. The same material with less give would feel like toothbrush bristles. So it's really the fact that there are very many narrow and flexible fibers making contact with your skin all at once that produce a furry feeling when brushed against.

To go even deeper, the micro-structure of those fibers plays a role as well. If the micro-structure is rougher (nano-scale pits), the additional friction will make the material feel rougher.

Edit: I would actually modify my argument (per the_epic_narwhal's question regarding the smoothness of leather) to say that the most important factor is not the fibrous nature, but the surface microstructure. If the fibers are smooth, and you brush your hand against them, you are essentially pressing them into a uniform surface, so it would be similar to brush your hand against a well worn piece of leather or other material with few surface imperfections.

184 points · 4 months ago

Not to mention the air between the hairs adding to the cushioning effect, especially for furs with a lot of thin hairs where the increased surface area adds to the amount of resistance the air has to overcome to escape.

Does the air resistance play a significant part in the feeling of "softness"? If anything, it would add a damping effect to the movement of hair. The inherent feel of soft results from: 1. material has smooth texture (low coefficient of friction) and 2. compressible. Air movement might not play part in either of the two conditions to define softness.

1 point · 4 months ago · edited 4 months ago

It adds to the dampening effect like you say, so any object coming in with velocity will be slowed more gradually - adding to the softness according to your conditions. Hair with air in between them has to be further apart than hair with no air between them, and as a result is compressible.

Not so much the air resistance, but more of the surface roughness and how much the material itself gives when we press on it. Without noticing it, we change the presure that we exert when feel things (either between our fingers or against a solid structure). This provides a lot of detail about the compressibility of the material and supplements our perception of texture.

Would moisture absorption capabilities in the material have an impact, too? I have mild eczema on my hands so I'm sensitive to things that dry my skin out, and materials that do this the worst are also soft. Dryer lint is the ultimate one--it's so soft but as soon as I toss it I have to moisturize or my hands will flare up. Folding clothes does this too. Or am I just reading causation into a correlation?

It might also be due to the detergents or softeners used on the fabric. It's hard to say since you've only noticed it on your hands.

I haven't noticed anything with dryer lint but I have to lotion my hands after folding laundry. Sometimes I have to lotion them before or during folding laundry because it becomes so dry it's painful.

Yeah sounds familiar. I don't actually know why it's happening but after enough life experience I've settled on absorption as the reason. I had a job in college in a hotel laundry room and it was a nightmare--that's what triggered the connection.

I don't think it's because they're soft per se but the fact that most soft things have the type of fiber structure that can pick up microscopic particles of whatever actually is the cause.

Think about a towel vs a flat piece of fabric.

Also get breakouts from certain things and I feel your pain, brother.

9 points · 4 months ago · edited 4 months ago

You are absolutely correct to say it depends on the micro-structure of those fibers, but the mapping from the structure of the surface or fiber to the actual friction values is very complex. It's not just a "oh, this is rougher, so it buzzes more". Fingers and skin actually respond to changes in friction quite differently than one might expect, and a surface that produces more or louder vibrations on the finger is not necessarily rougher, or smoother. It all depends on how the friction (or vibrations it creates) is patterned or structured. source

Also note, the finger and finger print seems to play a large role in the story too, highlightly certain spatial features, and storing energy at particular tactile frequencies. To simply think of furryiness as a property of the material and geometry is incomplete.

The fingerprint findings of this article are interesting. I research with vibrations on skins surface (literally buzzing), and since the Pacinian corpuscle is located so deep within the skin, we considered differences in fingerprints to be negligible. Even simulations including the skin consider the skin to be homogenous (which it definitely is not) or anisotropic (which it is, but is difficult to quantify). example source

But I agree completly with your statement

It all depends on how patterened or structured.

5 points · 4 months ago(2 children)
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2 points · 4 months ago(0 children)

Its the micron count and the amount of twist in the hair follicles.

A micron count of less than 25 micrometres feels smooth because of the width between nerve sensors on our skin. Over that it feels "scratchy". A cheap woollen jumper usually has a micron of 30 or more.

If you know how, it would be helpful to translate the fabric-specific jargon like "micron count" to general scientific terms like diameter and pitch.

Micron count is the width of the fibres in micrometres.

Cat fur is made from twisted fibres, which makes them springy and yield when touched.

I feel this answer is a great one, and I was also smiling through it thinking of petting my cats.

If you haven't petted a fluffy cat, go pet a fluffy cat. Outs a feeling like no other. Just make sure its friendly first.

Implanted Medical Devices | Embedded Design
1 point · 4 months ago

Microstructure is correct. Also its dryness. Very fine dust feels soft. Add water to any of the things you mention and they're slick or sticky.

53 points · 4 months ago · edited 4 months ago

We are used to thinking of the senses in the very basic categories we learned in elementary school - sight, hearing, touch, smell, touch. But what we experience is not raw sensory input, it is our brain’s interpretation of a variety of sources of information compiled together into a constructed perception of reality.

Touch is made up of a large number of individual systems and nerve types. Mechanoreceptors respond at a basic level to pressure and stretching, and there are several types that are specialized for certain kinds of sensation (soft pressure, deep pressure, sustained pressure, vibration):

Hair on our body serves to further enhance the variety of sensations we can perceive, as the mechanoreceptors attached to each respond to its complex movement.

Similarly, there are nerves for sensing temperature change, pain, the spatial position of our body and angles of our joints (proprioception), balance (inner ear hair cells), etc.

So back to your question - what makes something feel soft or furry?

There isn’t a sensory nerve type dedicated to furry things, or to wetness, or to the feeling of wind blowing. Rather, these are all interpretations our brain deduces based on the compilation of sensory information (or lack thereof!) it is receiving from all of the nerve types above. Brushing against something furry will incite a mixture of responses due to hair movement, light pressure, temperature change, etc, that fits the brain’s pattern for “fuzzy”. Proprioception plays a role here too, as our brain uses the position of our body (the finger touching the cat) in its interpretation of the tactile senses coming from contact with it.

This is a really good point, that the brain is taking in lots of stimuli, but for certain things, like fine texture, we are starting to make good headway into which receptors are used. It's probably the pachinian corpuscle, and maybe some of the meissner

This is correct - but the complete answer is not just that the tactile and lamellar corpuscles respond when touching fuzzy things, it’s the degree to which they respond while the others do not (ie, the holistic pattern of sensory responses from all nerve types) that the brain interprets as fuzzy.

Thank you!

Let me seize the opportunity and go on asking what comes to mind. So it's already that difficult at the sensory side?! Are the signals modulated? If they are, in what way? I guess at some level they start to share nerve tracts? Do the signals merge? Do they show resonances?

Really good explanation, thank you for this

2 points · 4 months ago

You seem to know a lot about touch, I have a disease they affects my sense of touch ,and you could help me with some questions? PM me please.

Friction. At a microscopic level, every surface looks very different. Your fingers/hands are pretty rough too. You feel something is "soft" when a material can slide around on your hand without tugging on it too much. Harder surfaces will give more resistance.

Fibers that are thicker and coarser like wool also are likely to feel rough to your hands in comparison to smaller and smoother fibers like silk.

Another factor is warmth. How insulating a material is can impact how it feels to you. Something made of metal will feel cold or hot to the touch depending on the temperature because heat flows readily between your hand and the surface. Something insulating like most animal hair fibers will not draw heat from you easily, making it feel warmer, which adds to your feeling of "softness".

The softness of fibers is called "microns" or "micron count" the higher the number, the softer the fiber.

Sorry in advance for not being good at inserting equations onto Reddit...

When your hand comes into contact with something, it is slowed by the force of the object on your hand. If the collision between your hand takes more time, the amount of force applied to your hand is less. If the object has "give," it will take time to deform, which increases the time of the collision between it and your hand, which decrease the amount of force it applies to you. If the object did not have as much give, the collision would take less time, which would mean a larger force acting on your hand.

This can be summed up by the concept of impulse, which is also defined as the change in momentum (final momentum minus initial momentum), which is equal to the net force acting on the object multiplied by the time over which that force acts.

The concept can also be approached through the common version of Newton's second law, net force equals mass times acceleration. The more rapid the acceleration of your hand during the collision with an object, the more force it will exert on your hand. Here, less give means less time, which means a greater acceleration, which means a greater net force.

Ok so how does that make things feel soft?

Less force applied to you by thing => thing applying force to you feels softer

Not exactly... The average resistance to motion is somewhat tactually perceptible, but it's not what we think makes up softness in general. It's actually more correlates with stickiness I believe (or tact).

I've held a tiger cub, a chimpanzee and many different dogs and cats.

Tiger cub was rough, chimp very rough; both happened at an animal sanctuary in Myrtle Beach (if that makes a difference). Outside dogs and cats seem to have rougher hair, I'm guessing the dirt in the oils on their fur make a difference, vs dust in house held dogs and cats.

So what actually makes the difference?

As other folks have mentioned, it's complicated, and to say we really know what makes the difference might be misleading. I also have done most of my work in surface texture (not something like fur) so my answer might not be the best here, but I'll try.

My guess is that it does come down to an interaction between oil and dirt which eventually causes a grittyness and coarsness to the sensation which you might call 'rough'. Instead of the sensations being regular and smooth, there is sorta a choppy and unevenness to them. It's probably a combination of how the animals hairs interact with each other and how the vibrations and patterns of displacement on your skin get transferred. Something like fur is so complicated that we don't (or I haven't seen) general models of how humans percieve it.

-4 points · 4 months ago(2 children)
4 points · 4 months ago(0 children)
5 points · 4 months ago(0 children)

It’s basically the concept of friction. If you run your hand against a smooth stainless steel door, it’s going to feel “softer” compared to running your hand against a cheese grater.

This isn’t the whole explanation though because there are plenty of things with give that do not feel soft, like wire mesh. And then you get to fine materials like steel wool which is soft but not particularly pleasant to rub.

Well, yes and no, I think. I was discussing if you poke something, but rubbing an uneven surface amounts to lots of little pokes. Though there is also the factor of pressure (force per unit area), which adds another dimension (two, technically, as it's surface area) to my answer above. Stuff like wire mesh or steel wool doesn't contact you on as large of a surface area (whether poking or rubbing), so the force it applies is larger than something which contacts you over a larger surface area.

So what’s the difference between soft cat fur and not as soft dog hair?

Dog hair is not made from twisted fibres, just straight fibres like human hair, so it doesn't yield as much.

8 points · 4 months ago · edited 4 months ago

To be quite honest, we don't actually know, and this is an incredibly active area of scientific research. There are explainations that focus on the actual makeup of of the material (geometry, stiffness, pile, etc), but these are incomplete, and don't really generalize. Then there are also explainations that look at the actual signals coming from the nerves in the skin (via mechanoreceptors) and try to quantify that. But each of these (and host of other explainations) are incomplete.

In general, touch is a very poorly understood sense, in part because we don't have the proper tactile "camera" or tactile "displays" to pick and poke at humans and actually figure out what is going on with tactile perception. No doubt we are getting better (we finally are starting to develop these cameras and displays, i.e. something like this) but there is a LOT of room to go. For instance, there is an academic conference next week discussing just these kinds of questions, and a whole workshop dedicated to this topic (link

To answer your exact question about velvet, what we think happens is this: you run your finger across a texture and the meshing of you finger and the velvet surface generates complex vibrations on the skin that the brain has figured represents velvet. Specifically, it is the spectrum of vibrations, or the frequency content of them, that we think the brain pays attention to source. It might be similar to how you can hear a note being played on a violin, and recognize the unique timbe (character) of that instrument (what it's made of, how it's put together, etc) source. In this way, you are kinda listening to the vibrations that are occuring on your finger as it moves across a surface. The jury is still out on that though, we just don't have the tech and experimental data yet.

Sorry if it's a bit of an undwhelming answer, I just spent years of research in this area, and it's still incredible to me how little we know about touch when compared to vision or audition. The scientific answer is that we just don't know. In the end, it really comes down to the fact that we've just have visual and audio displays much longer than touch displays, so we've been testing stimuli with real humans and asking them questions about it in audition and vision, but no so much in touch.

TL:DR we aren't really sure, but we're actively developing the hardware and techniques to find out. For velvet, it's probably the spectrum of vibrations that occur on your skin when you run your finger over it.

3 points · 4 months ago · edited 4 months ago

A material is soft when it provides enough give that it exerts very little or no localized pressure to your skin when you touch it. Meaning the pressure at one point on your skin is nearly identical to a point right next to it. The relevant distance between those points is the average distance between nerve endings in your skin. All other aspects of softness (that you can read about above) fall out of that feature. Usually, soft means fairly slippery, because otherwise the material would catch and provide localized pressure. Usually soft means stretchy and pliant, because otherwise the hammock effect would cause localized pressure. Usually soft means insulating because otherwise localized temperature differences can be mistaken as or accentuate local pressure differences. Softness varies from person to person not just based on personal criteria, but also because of variations in skin sensitivity. E.g. a pile of canvass might feel soft to your heel, but not to your elbow; or linen might feel soft to your elbow, but not to your cheek. (The only caveat to this is that some people require some small amount of friction or temperature difference to identify something as soft. This seems to be a cultural or linguistic determination. You can identify it by asking a person if they think warm water is soft. Some say yes, some say no.)

This is far from a complete answer, but another aspect of perceived “softness” has to do with the range of fiber diameters. If the range of a group of fibers is small (they are all similar widths) it will feel softer than a group of fibers with varying widths- even if this group has a smaller average fiber diameter.

Interesting but not something I am ready to believe without evidence.

2 points · 4 months ago · edited 4 months ago

The top comments are right in this sub but there is also one more element in cats(maybe dogs too but I don’t know). Their fur is also really clean. They spend a lot of time grooming. Their tongues have barbs on them witch comb out undesired debris. Their saliva contains bacteria which kills some unwanted guests, and also a detergent like component which cleans a cat to the point where you don’t even need to bathe it. Your sheets at home might be really soft. But if it’s dirty and grimy it will be less soft. So cats also have this advantage in addition to the ones listed.

Counter question: what makes velvet material catch on super dry hands if other people find it so soft? I absolutely cannot touch velvet without it feeling like the equivalent to the sound of nails on a chalkboard.

Me neither. It makes me sad. Dry skin has a bunch of little edges, flakes, and corners that stick up away from the surface (like the broken edge of a butterfinger candy bar) that catch and hold onto small fibers like those on velvet and make you want to, just, die.

This is also my research topic, but I'm coming at it from a completely different angle than MatSci or Physics; I'm in Biomedical Engineering studying the touch receptor (called mechanoreceptor) responsible for the sensation of high frequency vibrations and material textures. The Pacinian corpuscle is deep in your skin (deeper than other receptors that feel constant pressure and low vibrations) and is responsible for the perception of texture. When you rub your hand across any surface (need to rub - it doesn't work if you just poke it), this mechanoreceptor is activated, amplifying displacements on the skin as small as single microns (maybe even less, depending on the source). These receptors are mostly located in you hands, feet, lips, and genitals, where you are most sensitive to touch.

Without going into too much detail, we can identify textures, including "softness" but even more specific (such as the difference between different types of cotton), by the spectral compositions of the individual frequencies and intensities of the displacements on the skin's outter surface after they are amplified by this mechanoreceptor. Each receptor is at the end of a nerve, and the mechanical displacement is amplified and transformed into a nerve signal (that's an explaination for another day). Groups of these mechanoreceptors work together to give more information about the tactile sensation to notice small differences in space.

There are similarities between tactile perception and auditory timbre (how we can tell the difference between a human voice, a cello, and a tuba all playing the same note) and auditory consonance (how we consider a major key "happy" or a diminished chord "daunting"). Tactile softness perception is related to consonance, where some materials (that are felt at specific frequencies or combinations of frequencies) may be considered more "pleasing" or "softer." While I dind't know about the cultural differences in softness before reading these comments, I would imagine they are related to the consonance of the texture - everyone's mechanoreceptors are the same (with some pathological exceptions related to diseases) and process the information the same way, but the difference between someone interpreting the sensation as pleasing or not can differ (kind of how songs in minor keys can be considered "sad" or "hopeful" depending on the background).

tl;dr: Receptors in skin amplify and convert small surface displacements from textures to nerve signals. Some of these signal combinations are described as "soft."

1 point · 4 months ago · edited 4 months ago

softness can be described as the ability of some material to bend without creasing, and along with this, the lack of pressure or feedback (like a spring)[edit: this actually explains what is turgid, softness seems to exploit this on a molecular level but to truly be soft would require the same amount energy feedback to be comfy], where the energy input then becomes the output back into the original direction or otherwise(near it). Say I push into a spring and the spring pushes back. Beds are known for this aspect of springiness, and memory foam and other types of mattresses and covers suffer from the inability to provide enough feedback to be truly pliable and soft without creasing.

The softness of velvet likely has to do with the microstructure of this feedback, and so it is the molecules themselves or the structures of those molecules together, a lattice of sorts, that has feedback, rather than the entirety of the structure as a whole. This is probably that strange feeling of, not necessarily softness, but what appears to be like a vibration upon contact with the skin.

It should be termed perhaps as microfeedback or molecular feedback, where the molecules or the molecular structures themselves act as springs rather than the objects they form.

Imagine a bunch of springs at the molecular level, and touching them, they would mimic the same feeling.

Whether this is happening at a molecular level or a structural level, versus as an object, is a good question.

Since certain molecules like acids can sting, even in the slightest amounts, and this perception involves the sensory perception of a vibration that is very quick, and this sensory perception is not very quick, I will assume it is the molecules and not the structure they have formed as a whole(the nanostructure, which defines the difference between graphite and diamond, but not the sensory perception created by touching them). I'm really not entirely sure what that molecule would be that creates that feeling. Along with that as said by apl460, the surface below the microstructure will also change the perception or abilities of that molecule to interact with the skin( another surface), and hence surface areas, and the intermolecular forces involved with those surface areas and other bodies will change the way the behave.

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