story identification - Man creates miniature population on different time-scale; uses them to invent the 'absolute protection' dome

My dad has been trying to find the title of a short story for ages. According to him, the story goes like this:

A scientist who works on an island manages to create a miniature population with whom he can communicate. As time is proportional to their size, it goes way faster for them than the scientist, which allows the creatures to be able to make inventions humans can't yet.

The scientist, whom the creatures worship as a God, starts asking them to reveal how to make these inventions humans are unable to create. At one point, his miniature people end up developing the transport of wireless energy.

Because of the industrial lobby of the human world, the scientist and his people are under a death threat. He asks the creatures to develop the absolute protection, which they do, but this stops the communication between the scientist and his people. He can only see a grey dome in his microscope.

At the last moment, as missiles have been fired towards the island, a breach opens in the dome. The scientist gets a message from his creatures: they ask for forgiveness as they were not able to reach him anymore until then. He responds that if they want to be forgiven, they must amplify the action of the dome.

In the end, the whole island is covered with an indestructible grey dome that no one can see through.

Some parts might be added by my dad's imagination but if you find anything similar to this plot, we would be really grateful!

Answer

The description almost perfectly fits Microcosmic God by Theodore Sturgeon.

A highly secretive and reclusive biochemist named Kidder produces inventions that transform human life, spanning every aspect of science and engineering. Unbeknownst to anyone, Kidder has developed a synthetic life form, which he calls "neoterics." These creatures live at a greatly accelerated rate, and therefore have a very short lifespan and produce many generations over a short period of time.

This allows Kidder, by presenting them with a frequently changing environment, to "evolve" them quickly into highly intelligent lifeforms who fear Kidder and worship him like a god. Kidder can control his neoterics' environment, and thus force them into developing technology far beyond that of humans. While earlier inventions had been his own, Kidder created the neoterics with the intention that they would become the source of many newer and greater inventions which he could claim as his own.

Kidder's banker takes over the island on which Kidder has built his laboratory, hoping to use a neoteric design for a new source of power to take over the world. When the banker strikes to kill Kidder and the workers who had assisted in building the power plant, Kidder asks the neoterics to throw up an impenetrable force field.

The story ends years later. It is unknown whether or not Kidder is still alive under the shield, and certain that the neoterics have continued to develop technology far in excess of anything controlled by humans. The reader is left to suppose that, if the neoterics were to decide to take the Earth, nothing would stop them.