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Comment by hristov | Hacker News Reader

They did not mention whether it damages human skin. If it rips viruses apart how do skin cells fare? The way that researcher is gingerly holding the material with forceps without touching it does not inspire confidence.

Furthermore i know the high level development of the integrated circuit industry inspires other industries to try to make things from silicon wafers, one should keep in mind that silicon wafers are still quite expensive and probably too expensive for human scale objects. The reason they work for chips is that the silicon part of chips (without the plastic and copper packaging) tends to be very small.

These researchers should take a cue from the oled display industry and try to make their spikes in annealed amorphous silicon. That may be affordable enough to make stuff from.

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The top layer of skin is several layers of dead cells. This might act like sandpaper, but the bumps are less than the width of a single cell they aren't going to reach living skin cells by just holding it.

https://en.wikipedia.org/wiki/Epidermis

It's quite clever if you think about it. A virus can easily attack living cells but they aren't don't anything to a layer of dead cells. Similarly it doesn't need to be warm and moist to keep cells alive etc.

The spikes would be so small they wouldn't affect your skin cells. Viruses are magnitudes smaller than cells and your skins cells have thick, durable cell walls to protect them. It's no different than other materials like copper and silver that also exhibit natural antiviral/antibiotic properties. A piece of polished copper would feel smooth to the touch but if you looked at it under a high power microscope the surface would appear rough and jagged like the silicon spikes.

I wouldn’t assume the surface is going to maintain these precise nano structures after rubbing your finger across it.

So yes it might feel smooth, but IMO it could also feel gritty from structures larger than a single spike breaking off. It really depending on how exactly it’s made/ what it’s applied to not just the initial shape.

Animal cells do not have any thick, durable cell walls (like the cells of plants or of fungi). Their thin membranes would be easily ripped by such silicon spikes.

The durable materials, if any, can be only extracellular, like in bone tissues or cartilage tissues, where they fill spaces between and around the cells.

As another poster has said, the durable, protective part of the skin is made by dead cells, which are shed and renewed. Being already dead, they would not be affected by scratches.

On the other hand, eating some particles covered with such a surface with silicon spikes might be a bad idea, though the damaged cells from intestinal walls should also be eventually replaced, like those of the external skin.

> If it rips viruses apart how do skin cells fare?

Or maybe lung cells too, if you systematically inhale spikes that have broken off.

Oops, we made asbestos

"In this case, however, viruses are an order of magnitude smaller than bacteria so the needles must be correspondingly smaller if they are to have any effect on them."

And animal cells are an order of magnitude larger than bacterial cells, so I wouldn't worry about the spikes on my skin

The reason why you should not worry about the spikes on your skin is because the surface of your skin is made by dead cells.

Otherwise, the thickness of the cellular membranes is small in comparison with virus sizes and spike sizes, so these spikes should rip them apart too.

A mosquito is many orders of magnitude smaller than you, but you should still worry when it comes in contact with your skin, because it is not your size that matters, but only the thickness of your skin.

Ah, I see, that makes sense

"keep in mind that silicon wafers are still quite expensive and probably too expensive for human scale objects"

That is wrong. The expensive part in silicon chip production is the process. It's just that hard to make working circuitry close to the molecular scale and a lot of sophisticated technology had to be developed for it (i.e. a lot of R&D invested money), hence the high cost of production nowadays. Here however, it's about close to no fabrication process (by comparison) and the purity of the raw material involved will not matter that much either.

Silicon wafers come from a large single crystal that has to be grown. It's not a trivial engineering challenge, as you would suggest. There's a supply shortage for the entire semiconductor industry that is driving up prices.

> The way that researcher is gingerly holding the material with forceps without touching it does not inspire confidence.

They probably don't want to immediately clog it with their oily fat human sausages.

That's also my guess; however this would probably also mean it's too delicate to actually be deployed in a normal environment.

Asbestos fibers damage cells using the exact same nano mechanical concept these silicon needles do. So I would be more concerned with minute fragments of the material breaking off and being ingested than with skin damage but either way extensive safety validation is in order before this stuff is integrated into products.

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