Spider dragline silk as torsional actuator driven by humidity for applications as artificial muscle

Spider silk is a self-assembling biopolymer with hydrogen bonds underlying its chemical structure, yet despite weak chemical bonding it outperforms most materials relative to mechanical performance. The biopolymer is produced from the spider major ampullate gland and is an extraordinary fiber that can surpass most synthetic materials in mechanical toughness by balancing strength and extension/flexibility. Properties of spider dragline silk include high thermal conductivity, peculiar torsion dynamics and the potential for exceptional vibration propagation. To add more distinction to the natural fiber, spider dragline silk display a giant shape-memory effect upon exposure to water; in an effect known as supercontraction. The unique and remarkable properties of spider dragline silk are attributed to its hierarchical structure and morphology.