From foldable phones and wearable health monitors to lightweight solar panels, flexible electronics are a fast-growing area of materials engineering. But their durability under repeated bending and rolling has remained a major concern. A new study by engineers at Brown University shows that cracking in these devices is more complex than previously believed, and it points toward a promising strategy to address the problem.
Nitin Padture, professor of engineering at Brown University and corresponding author of the study, explained that the substrate can be compared to the foundation of a building. If the foundation cracks, the overall integrity of the structure is at risk. The work represents the first clear evidence that cracks in the fragile electrode layer can directly compromise the substrate itself.
Ranka, A., Layek, M., Kochiyama, S., López-Pernia, C., Chandler, A. M., Kocoj, C. A., Magliano, E., di Carlo, A., Brunetti, F., Guo, P., Suresh, S., Paine, D. C., Kesari, H., & Padture, N. P. (2025). Cracking in polymer substrates for flexible electronic devices and its mitigation. Npj Flexible Electronics, 9(1), 92. https://doi.org/10.1038/s41528-025-00470-z
The research, reveals that small cracks in the brittle ceramic electrode layers of flexible devices do more than interrupt conductivity. They can also drive deeper cracks into the underlying polymer substrate; the material long assumed to provide a crack-resistant foundation. Once cracks extend into the substrate, they act as permanent defects, weakening the entire structure and reducing the functional lifetime of the device.
Nitin Padture professor of engineering at Brown University stated,
“The substrate in flexible electronic devices is a bit like the foundation in your house. If it’s cracked, it compromises the mechanical integrity of the entire device. This is the first clear evidence of cracking in a device substrate caused by a brittle film on top of it.”
The study was prompted by observations from Anush Ranka, a postdoctoral researcher who conducted the experiments as part of his Ph.D. research in materials science at Brown. Ranka built small prototype devices with different combinations of ceramic electrode materials and polymer substrates. He then subjected them to repeated bending and used electron microscopy to examine how cracks developed. To probe beneath the ceramic layers, he applied a focused ion beam, effectively etching away the brittle top layer to reveal the condition of the substrate below. The results consistently showed substrate cracking wherever the electrode layer had fractured, regardless of the material combinations tested.
To better understand why this occurred, the team collaborated with mechanical engineer Haneesh Kesari and doctoral student Sayaka Kochiyama. Their analysis pointed to a mismatch in elastic properties between the ceramic and polymer layers. When the brittle electrode cracked, the stress distribution caused cracks to propagate downward into the softer polymer foundation.
Armed with this insight, the researchers proposed a solution. By introducing a third layer of material between the electrode and the substrate, it is possible to buffer the elastic mismatch. Using a computational design map, they identified polymers that could serve this purpose if applied at the right thickness. The team selected one candidate material, fabricated test devices, and demonstrated that the added layer reduced substrate cracking.
This approach has broad implications for the design of flexible electronics. While manufacturers have focused mainly on preventing cracks in the brittle ceramic films, the study shows that long-term reliability also depends on protecting the polymer base. By adopting a multilayer design strategy, engineers may be able to extend the cyclic life of devices subjected to constant bending.
The findings also provide a framework for future material selection. With a systematic design map in hand, engineers can explore hundreds of potential polymer interlayers to optimize durability across a range of electrode-substrate systems. This could accelerate the development of more robust wearable sensors, rollable displays, and portable photovoltaic devices.
As Padture summarized, the study essentially identifies a problem that had gone unnoticed and offers a practical path toward a solution. Recognizing that substrate cracking is a hidden failure mode in flexible electronics may help the field move beyond trial-and-error design, leading to more reliable technologies in both consumer and industrial applications.
Adrian graduated with a Masters Degree (1st Class Honours) in Chemical Engineering from Chester University along with Harris. His master’s research aimed to develop a standardadised clean water oxygenation transfer procedure to test bubble diffusers that are currently used in the wastewater industry commercial market. He has also undergone placments in both US and China primarely focused within the R&D department and is an associate member of the Institute of Chemical Engineers (IChemE).
