Directional Inner-Surface Printing for High-Resolution Conformal Electronics.

The direct fabrication of functional electronics on conformal surfaces enables efficient space utilization, higher integration density, and reduced structural weight in advanced electronic systems. While conformal electronics on planar and externally curved surfaces have been widely investigated, no effective approach has been developed for high-resolution fabrication on cavity inner surfaces. This limitation leads to substantial underutilization of inner-surface resources and restricts their functional potential. Inspired by the traditional Chinese art of inner-painted snuff bottles, we introduce a directional inner-surface printing method based on the principles of aerosol jet printing1,2 that maintains high printing resolution across a range of materials. Compared with conventional techniques, the method supports the direct fabrication of diverse functional electronics on inner surfaces with feature sizes  as small as 11.58 ± 0.67 μm, including electronic structures within high-aspect-ratio ( > 10) cavities and stress-sensor arrays integrated into honeycomb architectures. This strategy enables the fabrication of high-resolution, integrated electronics in previously inaccessible areas, with potential applications in structural health monitoring, wearable devices, and biotechnology.