Patent Primer

Beware: Prior Art and Public Disclosure

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When reviewing your patent application, patent examiners determine if your invention is novel and non-obvious in view of the prior art.

Prior art:

Prior art consists of information patented, described in a printed publication, in public use, on sale or otherwise available to the public as of the date you filed your patent application. Prior art includes publications, such as journal articles, presentations, posters or information on a website, as well as information known or used by another.

Inventor exception to prior art:

In the U.S., an inventor's disclosure of their own work made less than one year prior to the patent filing date will not count as prior art. This is referred to as a grace period for the inventor's own disclosure. If your public disclosure was made more than one year before your patent filing date, it is considered prior art. Caution: Your publications could spur similar or follow-on publications by others. These will count as prior art if they occur before your patent application is filed with the patent office.

International patenting and prior art:

In most countries outside the U.S., any public disclosure by anyone—including the inventors—prior to the patent application filing date is considered prior art and can be used to reject a patent application for lack of novelty or obviousness.

Examples of routine academic activities that may be considered public disclosures include:

  • Papers
  • Abstracts
  • Posters
  • Presentations
  • Grant applications
  • Online publications
  • Open thesis defenses
  • Department and campus seminars

Filing Date, Prosecution and Maintenance

Effective filing date:

The U.S. awards patents to the first-inventor-to-file and the effective filing date is used to determine who is entitled to a patent. The effective filing date is the date an application is filed that fully supports the claims. If two inventors invent the same idea independently and each files a patent application, the inventor with the earlier effective filing date is awarded the patent.


Patent prosecution refers to the written exchange between patent applicants and the patent office during the examination process.

Maintenance and term:

Most patents expire 20 years from the date of initial filing provided maintenance fees are paid at 3 1/2, 7 1/2 and 11 1/2 years from the date of issuance. Design patents based on decorative, non-functional designs receive protection for 14 years.