Laser Scribed Carbon Layers: Process Optimization & Sensor Applications

Justifiably large interest on graphene as an extremely versatile and high-conductivity flexible electronic material led to ongoing push for novel low-cost preparation techniques. Recently it has been demonstrated that polyimide (commercially available as Kapton®) films carbonizes in a surprisingly effective and simple fashion by illumination of medium power (~100mW) ns to ms range laser pulses in air. The resulting carbon layers have been shown to be of a random network of 3D and 2D graphitic structures that bestow the final layer sufficient conductivity (1 to 10 Ω-cm) that can be used in practical applications, especially for sensor and electrochemical applications. However, being a relatively novel process, a detailed account of process optimization and reliability of the conducting structures have not been yet provided, which is provided in this work. Moreover, additional examples of materials responsive to laser scribing process and passive RC-based sensors are also introduced. 1n addition, we methodically explore typical process parameter space to decouple the complex interplay between laser speed, pulse width, line spacing and laser power for the laser scribe process as well as investigating the longevity and statistical nature of device performance. 1n particular, we pay attention to humidity conditions and indicate how some of potential weakness can be turned to strengths for sensor applications. Therefore, we report on the optimal processing conditions, reliability of passive device performance and chemical stability of laser scribed carbon electrodes which can be applied to practical sensor development.