When someone develops a new product, process, or machine, he/she will often patent it to make sure no one else develops the same thing and takes credit for it. Are you wondering whether someone has made a device similar to the one you want to make? You can see if the product has been patented by searching in InnovationQ Plus, Derwent, or the US patent database.
InnovationQ Plus - InnovationQ is a powerful, user-friendly intellectual property analytics tool that helps you understand and optimize your company's intellectual property.
Derwent Innovations Index - Provides access to more than 14,800,000 patents with links to cited and citing patents, cited articles, and full-text patent data sources. Contains patent citation information
United States Full Patent Database - Patent search tool by the US Patent Office (slightly harder to use than the others).
SciFinder - A powerful database to identify chemistry and chemical related patents. It also includes citations to journal articles, patents, conference proceedings, dissertations, books, reviews, and technical reports. SciFinder: first time users registration.