Laser-induced graphene as electrode for wearable electronic devices

Laser-induced Graphene(LIG) is a porous material obtained by graphenization of polymeric substrate. The fabrication approach consists of exploiting the use of pulsed-laser writing, causing the absorpion of long-wavelength radiation, which produces photo-thermal effects. The purpose is to obtain Graphene from a wide range of carbon precursors under ambient atmosphere conditions. LIG opens up a lot of new ways in electronics, especially for flexible, biodegradable and edible electronics. Thanks to this technique conductive patterns can be obtained on planar and flexible substrates and used as electrodes for strain sensors and supercapacitors (SCs). The substrate used, in my thesis, is polydimethilsyloxane(PDMS) because of its wide use due to its rheological properties, low cost and biocompatibility. The resulted LIG patterns on PDMS are characterized in order to study conductivity. To improve it, a variation of laser parameters (power, frequency, velocity and others) is performed and different substrates mixed with PDMS are tested. The best mix results using triethylene glycol (TEG) and a study varying its percentage inside PDMS matrix is carried out. The optimum laser parameters onto pure PDMS and PDMS-TEG mixture are used to write strain sensors and supercapacitors. The samples were also analyzed by Scanning Electron Microscopy, Raman spectroscopy and XPS elemental analysis. Sheet Resistance are evaluated in 'flat and bending conditions'. The performances of SCs are obtained with electrical/electrochemical measurements such as cyclic voltammetry, electrochemical impedance spectroscopy and constant current charge/discharge. A final comparison between PDMS and PDMS-TEG in strain gauges and supercapacitors is carried out. An excellent result is that PDMS-TEG(40% in-weight) has a specific capacitance 100 times higher than pure PDMS-based devices.