By Andy Sullivan

WASHINGTON, Nov 20 (Reuters) - The U.S. Congress gave a big boost to a tiny technology on Thursday, voting to increase research funding that could lead to molecule-sized computers and medical robots that travel the human bloodstream.

The House of Representatives approved by voice vote a compromise bill that would earmark nearly $3.7 billion over four years to fund research in nanotechnology, the science of manipulating individual atoms to create new materials.

"The idea behind this bill is simple yet powerful: The American economy will grow bigger if America's scientists and engineers focus on things that are smaller," said House Science Committee Chairman Sherwood Boehlert, a New York Republican who sponsored the bill.

The Senate approved an identical bill earlier this week. President Bush is expected to sign the bill into law.

Nanotech firms have already introduced wrinkle- and stain-resistant cotton fabrics, food packaging that keeps meat fresh longer, and windows that are easier to clean. Boosters say microscopic computers, cancer-fighting molecules and nonpolluting automobile engines could be on the horizon.

Some environmentalists, including England's Prince Charles, worry about unintended side effects, such as the possibility that "nanorobots" could replicate like viruses and consume the whole planet, a scenario envisioned in author Michael Crichton's 2002 bestseller, "Prey."

The bill encourages research into the technology's possible social impact but does not earmark a dollar amount for that purpose.

Under a Clinton administration program, the government has already paid over $1 billion in nanotech funding over three years. The House originally earmarked $2.36 billion for the next three years, but the program was extended for another year in the Senate.

The National Science Foundation would control nearly half of the money, with the rest going to the Energy and Commerce departments, the National Aeronautics and Space Administration and the Environmental Protection Agency. The Defense Department, which also funds nanotech research, is not covered in the bill.