Browsing by Author "Samaraweera, R.L."

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    Development of a Silicone Dielectric Polymer for Actuators
    (Uva Wellassa University of Sri Lanka, 2021) Dissanayake, D.M.N.T.; Asela, A.U.; Premarathna, A.K.C.P.; Tennakoon, G.A.A.I.; Samaraweera, R.L.
    Virtual 3D environments (Virtual Reality) are created inside computers to deliver thermal, vibrational, and force feelings. Haptics technology brings this virtual world to end-users by haptics goggles and gloves. Tactile displays have been developed to deliver sensations in haptics gloves. In this regard, actuators act as movers in tactile displays stimulating sensations to skin receptors inside the fingertips. Dielectric polymer-based actuators are prominent in the world due to lightness, lower energy loss, and simplicity leading to wearable haptics gloves. Acrylic and silicone are the major types of dielectric polymers used for actuators. Silicone dielectric polymers have excellent properties such as faster response (3 s), efficiency, lower mechanical loss, and thermal stability comparing to acrylic. But silicones unable to achieve greater electro-strains (>10%) as it’s in acrylic-based actuators. This research work focused on enhancing the electro-strain property of silicone dielectric polymer by blending polyaniline particles. The electro-strain property of dielectric polymers depends on both dielectric constant and elastic modulus. Increased dielectric constant and decreased elastic modulus improve the electro-strain of actuators. Polyaniline has positive and negative charges itself which can be utilized to improve the dielectric constant of silicone polymer. Also, dispersed particles can change the elastic modulus of the matrix material. In the procedure, polyaniline and Dow corning silicone (DC 3481) were mixed in 0.0wt%, 0.5wt%, 1.0wt%, 1.5wt%, and 2wt% compositions and stirred for six hours. Next, thin films (thickness-125 m) were prepared using the Doctor blade technique on PVC (Polyvinylchloride) sheets. Crosslinking process was carried out for 24 hours. In characterization, 2wt% Dow corning silicone (DC 3481) and polyaniline polymer blend showed the 41.76% increment in dielectric constant, and elastic modulus was decreased by 68.71% compared to pure Dow corning silicone (DC 3481). This composition achieved the best matching electromechanical properties in dielectric constant and elastic modulus to apply in actuators. The developed polymer is recommended for haptics gloves to deliver enhanced force and vibration. Moreover, the Doctor blade technique can be introduced to fabricate thin films in actuators which is simple and cost-effective. Keywords: Virtual reality (VR); Actuators; Dielectric constant; Elastic modulus
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    Study of the Use of Natural Pigments Extracted from Nephelium lappaceum (Rambutan) Peel and Melastoma malabathricum (Maha Bovitiya) Seeds as an Alternative to Synthetic Acid-Base Indicators
    (Uva Wellassa University of Sri Lanka, 2020) Weerarathne, K.K.D.C.S.; Samaraweera, R.L.
    Acid-base indicators are widely used for visual detection of the endpoint of an acid-base titration. Most of these indicators are organic dyes of synthetic origin. These are hazardous, expensive, and harmful to the environment. Natural pigments in plant extracts such as Anthocyanin are highly colored substances that can change color at certain intervals of pH. This study was designed to examine the indicator activity of methanolic fruit extract rich in Anthocyanin as an alternative to synthetic indicators. Extracts from the selected plants prepared using a sonication technique were screened for their use in acid-base titrations. They performed promisingly in the strong acid-strong base, strong acid-Weak base, and strong base-weak acid titrations. Sharp and clear color change from reddish-brown to yellow for the Nephelium lappaceum peel extract and blue to red for the Melastoma malabathricum extract were observed. The indicator dissociation constant values that were determined using a spectrophotometric method for Nephelium lappaceum and Melastoma malabathricum were about 6.22 ± 0.06 and 4.22 ± 0.05, respectively. These values indicate that the pH ranges for the pigments investigated in this study are comparable to that of the synthetic indicators. These extracts were costeffective, easy to extract, and eco-friendly yet performed exceptionally in acid-base titrations. Thus, studied natural pigments would be a potential candidate to replace the commercial synthetic indicators that are used in laboratories. Further, there is no commercial value for the peel of Nephelium lappaceum and Melastoma malabathricum seeds. This study exhibits the potential of converting these readily available materials into many useful value-added products. Keywords: Natural pigments, Indicator, Low-cost, Value-addition, Titrimetry