Flexible Laser-Patterned Carbon Coatings for Sensing and Energy Applications

Fabricating electronic devices from natural, renewable resources has been a common goal in engineering and materials science for many years. In this regard, carbon-based coatings are of significance due to high availability of the raw materials and their environmental degradability. Carbonized materials and composites thereof have been proven as promising candidates for a wide range of future applications in flexible electronics, optoelectronics, energy storage or catalytic systems [1]. On the industrial scale, however, their application is inhibited by tedious and expensive preparation processes and a lack of control over the processing and material parameters. A promising tool to tackle that challenge is carbon laser-pattering (CLaP) allowing for the defined and site-selective synthesis of functional carbon-based materials for flexible on-chip applications [2]. Versatile inks, based on naturally occurring (molecular) starting materials are used to produce films, which are carbonized with a CO2-laser to obtain functional patterns of conductive porous carbon networks [3]. By chemical and physical fine-tuning of the laser patterned carbons (LP-C), we developed high-performance flexible resistive chemical and mechanical sensors. Their properties make them applicable in many fields e.g., robotics, bionics and even health monitoring. In this contribution, we present both, the material’s synthesis and tailored properties as well as in-depth microscopic and spectroscopic cross-sectional analyses of such coatings by advanced transmission electron microscopy, which provide unprecedented insights into the microstructure and local chemistry/bonding of laser-patterned carbon [4]. In that regard, we discuss the challenging cross-sectional preparation of such porous and sensitive structures by advanced ultramicrotomy. The gained insights in structure formation and local functionality pave the way for the utilization of alternative fast, large-scale carbonization methods such as rapid thermal annealing. [1] D. Jariwala, V. K. Sangwan, L. J. Lauhon, T. J. Marks, M. C. Hersam, Chem. Soc. Rev. 2013, 42, 2824–2860. [2] R. Ye, D. K. James, J. M. Tour, Adv. Mater. 2019, 31, 1803621. [3] S. Delacroix, H. Wang, T. Heil, V. Strauss, Adv. Electron. Mater. 2020, 6, 2000463. [4] M. Hepp, H. Wang, K. Derr, S. Delacroix, S. Ronneberger, F. Loeffler, B. Butz, V. Strauss, NPJ Flex. Electron. 2021, accepted for publication