The design and development of the plasma pressure jet is used throughout the thesis. The plasma jet's key components are discussed. Helium, argon, nitrogen, and air plasma were used to study the surface activation and bonding of cyclic olefin polymers. The plasma gas had a temperature less than 50 °C, making it suitable for polymer processing. The substrates were treated between 3 to 20 mm from the plasma exit. Air, as the plasma jet's feeding gas, creates a surface wettability of less than 10°. Water contact angle (WCA), scanning electron microscopy (SEM), atomic force microscopy (AFM), and infrared spectroscopy (IR) were used to characterise the substrate surface properties. This study establishes atmospheric pressure plasma as a cost-effective method for making cyclic olefin polymers hydrophobic and super hyderophilic. Secondly, design expert V12 software was used to optimize the APPJ operating parameters to obtain the lowest COP water contact angle with the lowest pricing. More research is required to optimise the polymer's surface and reduce the number of repetitive experiments. Therefore, the plasma jet was detailed to better facilitate understanding. Voltage and current probes were used for electrical measurements, and optical characterisation was performed using optical emission spectroscopy. Hydrophobic recovery of polymers is a concern in a variety of applications, most notably microfluidic devices. The work presented in Chapter 5 resulted in a stable surface that remained stable for more than 60 days and was partially stable for approximately 180 days. Finally, we modified the surface of disposable glass for biosensor applications. In order to improve the optical properties, the gold of different thickness can be tailored in this work by varying plasma jet parameters. The surface treated was characterised using UV-VIS spectroscopy and scanning electron microscopy. Although the results were not suitable for biosensor applications, the experiment was worthwhile.