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In this present work, we aim to improve the hydrophobicity of a polydimethylsiloxane (PDMS) surface. Various heights of 3D PDMS micropillars were fabricated via grayscale photolithography, and improved wettability was investigated. Two approaches of PDMS replication were demonstrated, both using a single master mold to obtain the micropillar arrays. The different heights of fabricated PDMS micropillars were characterized by scanning electron microscopy (SEM) and a surface profiler. The surface hydrophobicity was characterized by measuring the water contact angles. The fabrication of PDMS micropillar arrays was shown to be effective in modifying the contact angles of pure water droplets with the highest 157.3-degree water contact angle achieved by implementing a single mask grayscale lithography technique.

Even though heavy metals are naturally occurring compounds, in recent years, anthropogenic activities have introduced them in excessive quantities to different environmental matrices, imposing severe threats to the ecosystem. This chapter is focused on the occurrence of heavy metals in Malaysia, reviewing their potential sources, their existence in water, sediment, and aquatic life. However, despite the contents of heavy metals found in water, sediment, and aquatic life, they remain within the permissible limit. Heavy metals are known to be nondegradable and hence can lead to bioaccumulation in humans or animals. Avoiding heavy metals from entering the environment is, therefore, critical. From the literature survey undertaken in this chapter, it appears that the leading cause of heavy metal pollution in rivers is from industrial establishments and perhaps from the inadequate treatment of heavy metal–polluted wastewater discharging into rivers. Therefore treating wastewater is essential to ensure that no heavy metal ions are released into the environment. In undertaking this initiative the initial step is by having a proper detection device such as having sensors that can monitor the concentration of different types of heavy metal ions found in wastewater. Among the various technologies that are available, sensors utilizing nanostructured transition metal oxide are seen as an effective technique for the detection of various metal ions. The removal of heavy metal ions from wastewater can be accomplished in several ways of which metal oxide has been used for removal purposes. Clay and traditional oxides have also been used as an effective absorbent for highly concentrated heavy metal ions in wastewater, whereas nanostructured metal oxide semiconductors can be used to absorb and reduce the minute amount of heavy metal ions via photocatalysis process.

This paper presents the framework and control of a proposed water strider-liked robot, named as Portable Striding pH Tester (PSpHT) that is able to measure the water quality. PSpHT is designed with its leg and tip configurations made respectively from the light-steel beam and polypropylene-based material. The design of the leg is calculated and fabricated using Archimedes' principle. In addition, real-time software for use in a remote controlled pH data logger that strides the robot, called PSpHT-VI, is developed using radio frequency (RF) communication. The PSpHT is verified and validated by running two specific tests, which are striding topology test and real-time data Potential Hydrogen (pH) reading test. The tests were conducted in a lake within the campus of the Universiti Malaysia Pahang, Pekan.