Abstract: Composite sensors that exhibit four deformation modes decoupled from each other are disclosed. The modes include tension, compression, bending, and torsion. In one exemplary embodiment, the sensor includes a substrate and six unit sensors. The unit sensors are paired such that each pair includes two unit sensors disposed on opposite surfaces of the substrate, the sensors being substantially opposed to each other. Two of the pairs include longitudinal axes that are substantially parallel to each other, and the third pair includes a longitudinal axis that is substantially perpendicular to the other two longitudinal axes. The substrate is constrained along one of its edges. The composite sensors can be used in many contexts, such as part of a flow-driven, soft robot that passes through a pipe and detect links. Methods of detecting leaks are also described.