Under U.S. Patent law, any person who invents or discovers any new and useful process, machine, manufacture, or composition of matter, or any new and useful improvement thereof, may obtain a patent.  In order to obtain a patent, the following four requirements must be satisified:

Patentable Subject Matter.  An invention is a solution to a technical problem.  Moreover, in the U.S., a mere idea is not patentable.  Rather, a patentable invention must be claimed as one or more of the following:

• a machine (device or apparatus)
• a manufactured article
• a new composition of matter (a combination of ingredients)
• a process or method (of operating, making or using something).

Still, certain inventions are not patenable by themselves.  Such inventions include mathematical formulas, laws of nature and naturally occuring substances.  However, if your invention incorporates a mathematical formula or law of nature, you may be able to patent your invention.  For example, while a naturally occuring bacterium is not patentable, a pure culture or new use of the naturally bacterium may be patentable.  

Utility.  In order to have utility, an invention must actually accomplish something, such as solve a technical problem.  The invention cannot be inoperable (e.g., a perpetual motion machine) or frivolous.  However, in practice, almost any invention that works is considered to have utility.  Thus, few inventions are found to lack utility.

Novelty.  Novelty means that the invention must be new.  In order to be considered new, the invention must not already exist in the public domain.  A patent search is extremely helpful in determining whether your invention is novel.  Please be aware that if you publish (e.g., in a magazine or journal) or begin selling your invention, you have one year in which to file a patent application.  If you fail to file a patent application within this one year, you will be unable to obtain a patent on your invention.

Non-obviousness.  In order to be considered non-obvious, the invention must not have been so close to something already in the public domain that it would have been obvious to a person skilled in the art to which it pertains.  A patent search is helpful in determining whether your invention is non-obvious.