"From Molecular Diffusion to 2D Composites: Designing Encapsulation for Stretchable Organic Electronics"
Stretchable electronic devices promise conformal integration with skin and tissue for wearable and implantable applications. Encapsulation, however, remains the limiting requirement for their deployment. The intrinsic low density that permits deformation also allows the transmission of water vapor, oxygen, and ionic species, which degrade charge transport and shift device operating parameters. While hermetic barrier layers are well established for rigid devices, their translation to stretchable systems remains underdeveloped. Multilayer inorganic architectures cannot accommodate strain and are complex and costly to deposit, and the polymeric barriers used in their place are either too permeable or stiff enough to dominate the mechanical response of the device they protect. As a result, existing stretchable encapsulation strategies typically trade barrier performance against compliance or rely on processing routes that do not scale. Achieving both properties within a single solution-processed layer remains an appealing area for expanding the class of compliant barrier materials and their applications, particularly in soft electronics.
This dissertation explores spatial control of composition as a route to stretchable encapsulation, spanning length scales from tens of nanometers to hundreds of micrometers. We present a solvent-mediated functionalization method that programs the depth to which a fluorinated small molecule penetrates a semiconducting blend, tuning incorporation from surface-enriched gradients to uniform through-thickness modification. We show that these composition profiles govern device stability, and that the densest surface layers improve barrier performance at a measurable cost to modulus and charge injection. We further develop encapsulation as a discrete overlayer, dispersing hexagonal boron nitride platelets in an elastomeric matrix such that barrier improvement arises from tortuosity rather than from repeated deposition of dissimilar layers, and establishing the coating conditions that align them. Together, these studies provide a foundation for stretchable encapsulation designed around where material sits within a compliant film as well as the methodologies needed to understand each system. We anticipate this work will inspire expansion into device-integrated barrier systems.
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