Flexible Carbon-based Urea Sensor by Laser Induced Carbonisation of Polyimide

Pyrolysis of patterned polymers is a widespread technique for obtaining miniaturised carbon structures and devices. This process is performed at ≥ 900°C, which limits the device fabrication to rigid, high-temperature resistant substrates such as silicon. We obtain carbon patterns on commercially available polyimide films by a controlled laser writing, which induces a pyrolysis-like effect and causes the partial conversion of the polyimide into an electrically conductive, high-surface area carbon material. These flexible carbon patterns are characterised using microscopic and spectroscopic techniques, and are used as electrodes for the electrodeposition of chitosan. Subsequently, urease enzyme is immobilised on the chitosan film, and this composite electrode assembly is used for pH-based urea detection. This lithography-free, low-cost, and rapid fabrication process is capable of polyimide surface patterning with any desired shape in the micro- to millimeter range. Electrodeposited chitosan films can be used for the immobilisation of a variety of enzymes and chemical moieties for biosensing applications.