Embedding topography in Flexible Substrates enables control of crack propagation.

There is a current need to ensure that conformal electronics remain robust. The ability of these circuits to function even while damaged would therefore be beneficial. Our research explores the ability to control crack propagation in compliant membranes upon which flexible electronics can be printed. This control could prevent cracking in regions critical to device functionality. Our results first demonstrate that single layer membranes containing topographical channels can redirect crack pathways by up to 30 degrees. Here, cracks propagate along the thinnest part of the film when channels are sufficiently deep. Coating a second layer results in membranes that appear homogeneous and uniform in thickness. The embedded topography however also governs crack propagation; reorienting crack pathways by up to 45 degrees. Here cracks follow delamination pathways between the two layers. However, crack reorientation results in mode 2 fracture; limiting the extent of this control. The use of step wise pathways with alternating angled and parallel segments, along with parallel embedded channels, help regain control of crack propagation.

The Small Scale Systems Integration and Packaging Center at Binghamton University.