Continuous monitoring of gas molecules in the environment is very important in modern society. With the start of the industrial age, more pollution and toxic gas production has been produced and can endanger our healthy lives. To monitor such gas molecules, numerous gas sensors have been researched and utilised. These gas sensors are usually categorised based on their detection method, such as electrochemical, optical, piezo electric, pressure, humidity, and metal oxide semiconductor detection. In the past ten years, electrochemical gas sensors have been the most researched and the most used industries. Electrochemical gas sensors can be categorised into two systems, amperometric and potentiometric gas sensors. Challenges in former gas sensor designs arise from the volatile aqueous or organic electrolytes which are unable to withstand harsh environments such as high temperatures or dry conditions. Even under normal atmospheric conditions, the electrolytes are prone to drying out which can result in sensor failure. Membranes can reduce the evaporation rate of the electrolyte, but they are incapable of resolving the problem completely. In this thesis, we described strategies to fabricate robust and “membrane-less” electrochemical gas sensors with improved overall performance, using ionic liquids as substitute electrolytes. First, microcontact printing was utilised to fabricate miniaturised ionic liquid microstrips-based electrochemical gas sensors. Functionalised ionic liquids with thiol-group were synthesised and used for the fabrication of the ionic liquid microstrips sensor. The enhanced stability of the microstrips was observed with using the functionalised ionic liquids when compared to conventional ionic liquids. The performance of the ionic liquid microstrip-based gas sensor is further improved using several approaches, which includes the addition of a magnetic nanostirrer to enhance the mass transport of gas molecules into the electrode and the deposition of microstrips of platinum nanoparticles catalyst into the electrode. The former approach is demonstrated as an oxygen sensor in the range of volume fraction of O2 of 50 to 500 ppm giving a linear calibration with a iii sensitivity of 1.94 nA cm−2 ppm−1. The latter approach is demonstrated as an amperometric gas sensor to detect and measure oxygen and hydrogen gas in the range of 500 ppm to 10000 ppm giving an excellent linear calibration with a sensitivity of (5.41 ± 0.10) nA cm-2 ppm-1 and (1.68 ± 0.04) nA cm-2 ppm-1, respectively. Furthermore, the approach of designing ionic liquid based electrochemical gas sensor using microelectrode was investigated using an interdigitated microelectrode array. A redox recycling amplification scheme using a reversible gas analyte, such as oxygen was investigated. The loop of redox reactions enhances the measured current, leading to high sensitivity (3.29 ± 0.06 nA cm−2 ppm−1). Additionally, a novel detection method of carbon dioxide was investigated using the blocking of the redox recycling amplification scheme. A linear trend line is achieved using the proposed sensor design to measure carbon dioxide concentration from 2000 to 15000 ppm with a sensitivity of (0.030 ± 0.001) nA ppm-1.