Richard Aiken wrote:
>> OK, so now you have lots of robots on the outside of the victim.
> Not necessarily. A water cannon delivers a high-pressure spray,
> usually against (at least in the real world) lightly-clad civilians in
> a shirtsleeve environment. A lot of that water is going to end up in
> faces, which means eyes, ears, mouth, etc.

If skin or mucous membranes haven't been breached, they are still
outside as far as internal organs and systems are concerned.

> Will the speed vary in different tissues?
> So . . . a few seconds to make their way through the sinus passages
> and into the brain stem?

The speed range previously posted was for cells moving under their own
power through water.

Body tissues will be different to water in all sorts of ways: lipid
content, charge, dissolved ions and non-ionic solutes, etc. which will
influence how fast our hypothetical robots can move.

Overall, the fastest way to move through an animal is to hitch a ride in
the circulation.

>> What proportion are destroyed before they reach the target?
> I'd say not very many, assuming an appropriate outer coating.

The tiers of defense that constitute innate and adaptive immunity are
very effective at recognising and dispatching intruders.

As an example, you cannot get a secondary bacterial pneumonia unless the
flu virus has wiped out at least 70% of of alveolar macrophages. The
bacteria need to breach the layers of pre-formed antibodies, lytic
substances, white cells, etc. in the upper airways to get to the alveoli.

Remember that the incubation phase of a disease is the period in which a
pathogenic agent attains parity with the defense - the agent increases
in number while facing attrition by the defense, and vice versa.

So onset time will be fastest if host immunity can't affect the intruder
at all, and progressively slower or ineffective with increased net
clearance.

As previously noted, the lower bound is 10-15 seconds, equivalent to an
intravenous injection.

>> How many get lost (navigation errors)?
> I have no clue. :)

You need to have some value or range of values to come up with a
non-SWAG estimate.

Onset time will be a function of how quickly the robots can get to their
targets, how many are needed to generate an effect and how quickly the
effect can be generated.

The dose required will be a function of the required onset time, and how
much wastage there will be (immune attrition, navigational and power
failures, false positives in target identification, etc.)

> Could we add something to turn the mucus - perhaps even the skin - of
> people dosed with the compound a vibrant orange (or some other strange
> color)?

If the dye is brought along by the nanobots, that increases the payload
and overall dose required.

If the dye must be made on-site, then that further increases the onset
time until a detectable colour change. There may be knock-on effects
from local scavenging of the raw materials to make the dye.

How the dye is dispersed matters to onset time. Diffusion is the
ultimate limit to rate, which is a function of solubility in the skin.

Pigments that are invisible to human vision, but can be seen by
sensitive (nanograms per mL concentration) infrared or ultraviolet
fluorescence detectors might make more sense for a given dystopic
enforcement apparatus.

Rob O'Connor