SEPARATION OF NEUTRALLY-BUOYANT AND NON-BUOYANT PARTICLES BY A SPIRAL MICROCHANNEL: EXPERIMENTAL STUDY

Abstract

Different methods, including membrane-free devices based on inertial microfluids technology, were successfully investigated for the quick separation of particles from the carrier fluid. Nevertheless, the performance and application of majority of these devices are limited to neutrally or negatively buoyant particles. A through experimental research based on specially designed spiral microchannel for separating a mixture of neutrally-buoyant and non-buoyant particles types is carried out in order to create filtration devices that can manage both particles types. To separate neutrally buoyant particles, inertial microfluidics has been used through a spiral microchannel of constant cross section. It has been shown that while passing through the spiral microchannel, neutrally buoyant particles are equilibrated at the outer edge of the spiral channel which can be separated by providing branching. The role of number of turns in the spiral design has been tasted and benefit of more turns in obtaining higher separation efficiency has been obtained. For separation of non-buoyant particles from the matrix fluid, alternate contract and expansion zones have been tried in the microchannel spiral design. It has been shown that while passing through the contraction and expansion zone, non-buoyant particles is thrown outward progressively which can be collected by providing multiple branches at the end. Effect of pitch between contact-expansion zone on the efficiency of separation has been tested by preparing short, regular, and long pitches of contact-expansion zone in the spiral microchannel. The filtration ability of regular design of contraction-expansion has been shown to be superior. A combined design of spiral microchannel with appropriate number of turns followed by regular contraction expansion zone has been fabricated. The same has been tested and shown to be very efficient in separating a combined mixture of neutrally buoyant and non-buoyant particles. An earlier design of medium scale water filtration kit has been fabricated and assembled to show the ability of filtering flood water to drinkable water. Two different flood water samples have been tested and effectiveness of the fabricated prototype have been confirmed. To make the prototype user-friendly and informative, design and fabrication of TDS sensor in the kit has been performed. The fabricated unit with instrumentation can filter adequate flood water to drinkable water for a community having low resource setting.