In mechanical engineering, compliant mechanisms are flexible mechanisms that transfer an input force or displacement to another point through elastic body deformation. These are usually monolithic (single-piece) or jointless structures with certain advantages over the rigid-body, or jointed, mechanisms.
Since the compliant mechanisms are single-piece structures, there is no need of assembly. With no joints, "rubbing" between two parts or friction as seen at the joints of rigid body mechanisms is absent. Compliant mechanisms are elastic. They do not have the backlash common in rigid-body, jointed mechanisms. They are cheaper to make than the jointed variety.
Compliant mechanisms are usually designed using two techniques, the first being a pseudo-rigid-body model and the second, the topology optimization. Other techniques are being conceived to design these mechanisms. Compliant mechanisms manufactured in a plane the have motion emerging from that plane are known as lamina emergent mechanisms (LEMs)
The flexible drive or resilient drive, often used to couple an electric motor to a machine (for example. a pump), is one example. The drive consists of a rubber "spider" sandwiched between two metal dogs. One dog is fixed to the motor shaft and the other to the pump shaft. The flexibility of the rubber part compensates for any slight misalignment between the motor and the pump. See rag joint and giubo.
Compliant mechanisms are found in micro-electromechanical systems. For example, amplifying compliant mechanisms are used in micro-accelerometers and electro-thermal micro-actuators.
On Dec 17, 2007, the first International Symposium on Compliant Mechanisms was held at the Indian Institute of Science, Bangalore.
The Second International Symposium on Compliant Mechanisms (CoMe2011) was held on May 19-20th 2011 at Delft, The Netherlands.
For a comprehensive list of references on synthesis of compliant mechanisms check the wiki page from the Interactive Mechanisms Research Group