Graphene Oxide and Polymer Humidity Micro-Sensors Prepared by Carbon Beam Writing

Abstract

In this study, novel flexible micro-scale humidity sensors were directly fabricated in graphene oxide (GO) and polyimide (PI) using ion beam writing without any further modifications, and then successfully tested in an atmospheric chamber. Two low fluences (3.75 × 1014 cm−2 and 5.625 × 1014 cm−2) of carbon ions with an energy of 5 MeV were used, and structural changes in the irradiated materials were expected. The shape and structure of prepared micro-sensors were studied using scanning electron microscopy (SEM). The structural and compositional changes in the irradiated area were characterized using micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Rutherford back-scattering spectroscopy (RBS), energy-dispersive X-ray spectroscopy (EDS), and elastic recoil detection analysis (ERDA) spectroscopy. The sensing performance was tested at a relative humidity (RH) ranging from 5% to 60%, where the electrical conductivity of PI varied by three orders of magnitude, and the electrical capacitance of GO varied in the order of pico-farads. In addition, the PI sensor has proven long-term sensing stability in air. We demonstrated a novel method of ion micro-beam writing to prepare flexible micro-sensors that function over a wide range of humidity and have good sensitivity and great potential for widespread applications.

Patterning of COC Polymers by Middle‐Energy Ion Beams for Selective Cell Adhesion in Microfluidic Devices

“…The ion irradiation, in this case with predominant electronic stopping, leads to bond scission, and oxygen from the surrounding atmosphere can diffuse into the open structures of polymers and be captured in the defects. [ 63,83 ] The hydrogen release can be caused by the cleavage of macromolecular chains and the formation of free radicals, predominantly in the electronic stopping mode. [ 84 ] The hydrogen reduction can be attributed to the oxygen introduction to the structure of the polymer.…”

Recent Study Advances in Flexible Sensors Based on Polyimides

“…In order to improve the sensitivity of the sensor, carbon black [ 60 ], lithium chloride, graphene [ 61 ], halloysite nanotube [ 62 ], and poly(glycidyl methacrylate) [ 63 ], and so on are doped into PI to form a composite material as a new sensitive layer.…”

“…Although the repeatability of the sensor is not good enough and the dehumidification response needs to be improved, this work still proves that the improved PI structure plays an irreplaceable role in improving the performance of the humidity sensor. In order to improve the sensitivity of the sensor, carbon black [60], lithium chloride, graphene [61], halloysite nanotube [62], and poly(glycidyl methacrylate) [63], and so on are doped into PI to form a composite material as a new sensitive layer.…”