  Stretchable conductors are of crucial relevance for emerging technologies
such as wearable electronics, low-invasive bioelectronic implants or soft
actuators for robotics. A critical issue for their development regards the
understanding of defect formation and fracture of conducting pathways during
stress-strain cycles. Here we present a novel atomic force microscopy (AFM)
method that provides multichannel images of surface morphology, conductivity,
and elastic modulus during sample deformation. To develop the method, we
investigate in detail the mechanical interactions between the AFM tip and a
stretched, free-standing thin film sample. Our findings reveal the conditions
to avoid artifacts related to sample bending modes or resonant excitations. As
an example, we analyze strain effects in thin gold films deposited on a soft
silicone substrate. Our technique allows to observe the details of microcrack
opening during tensile strain and their impact on local current transport and
surface mechanics. We find that although the film fractures into separate
fragments, at higher strain a current transport is sustained by a tunneling
mechanism. The microscopic observation of local defect formation and their
correlation to local conductivity will provide novel insight to design more
robust and fatigue resistant stretchable conductors.
