A strain sensor includes a viscous piezoresistive element embedded or encapsulated within a solid, flexible, resilient packaging element, and a contact contactable from the exterior of the strain sensor and defining an electrical path through or along at least a portion of the viscous piezoresistive element, the resistance of the electrical path varying with deformation of the strain sensor. The invention allows the high gauge factor of a viscous piezoresistive material to be taken advantage of in a practical device by containing the material within a packaging element. The packaging element ensures a consistent output response as a function of deformation of the strain sensor and enables the strain sensor to detect time-varying forces due to the resilient nature of the packaging element.