Flexible electronics, also known as flex circuits, encompass various technologies that are used for assembling electronic circuits by mounting electronic components on flexible plastic substrates, such as polyimide, PEEK, or transparent conductive polyester film. Additionally, flex circuits can have the form of screen-printed silver circuits on polyester. Flexible electronic assemblies may be manufactured using identical components used for rigid printed circuit boards, allowing the board to conform to a desired shape or to flex during its use.

Flexible printed circuits (FPCs) are developed using photolithographic technology. An alternative approach to making flexible foil circuits or flexible flat cables (FFCs) is laminating very thin (0.07 mm) copper strips in between two layers of PET. These PET layers, typically 0.05 mm thick, are coated with an adhesive that is thermosetting, and will be activated during the lamination process. FPCs and FFCs have several advantages in many applications:

Flex circuits are often used as connectors in various applications where flexibility, space savings, or production constraints limit the serviceability of rigid circuit boards or hand wiring.

Most flexible circuits are passive wiring structures that are used to interconnect electronic components such as integrated circuits, resistors, capacitors, and the like; however, some are used only for making interconnections between other electronic assemblies either directly or by means of connectors. Consumer electronics devices make use of flexible circuits in cameras, personal entertainment devices, calculators, or exercise monitors. Flexible circuits are found in industrial and medical devices where numerous interconnections are required in a compact package. Cellular telephones are another widespread example of flexible circuits.

A common application of flex circuits is in input devices such as computer keyboards; most keyboards use flex circuits for the switch matrix.

In LCD fabrication, glass is used as a substrate. If thin flexible plastic or metal foil is used as the substrate instead, the entire system can be flexible, as the film deposited on top of the substrate is usually very thin, on the order of a few micrometres.

Organic light-emitting diodes (OLEDs) are generally used instead of a back-light for flexible displays, making a flexible organic light-emitting diode display.

Flexible batteries are batteries, both primary and secondary, that are designed to be conformal and flexible, unlike traditional rigid ones.