A method of evaluating the effectiveness of an asphaltene inhibitor comprising the steps of: i) providing a microfluidic device configured to rotate about an axis and an optical detection system, wherein the microfluidic device comprises an oil sample reservoir (110, 610) and a precipitant reservoir (114, 614) integral to the microfluidic device, at least one mixing chamber (119, 619a) integral to the microfluidic device and in fluid communication with the oil sample reservoir (110, 610) and the precipitant reservoir (114, 614), and an analysis chamber integral to the microfluidic device and in fluid communication with the at least one mixing chamber (119, 619a), and wherein the optical detection system is configured to measure optical properties of fluid in the analysis chamber; ii) filling the oil sample reservoir (110, 610) and the precipitant reservoir (114, 614), respectively, with an oil sample/inhibitor mixture and a precipitant; iii) rotating the micro fluidic device to generate centrifugal force to cause at least a portion of the oil sample/inhibitor mixture and precipitant to travel radially outward from the oil sample reservoir (110, 610) and the precipitant reservoir (114, 614) into the at least one mixing chamber (119, 619a) in which the at least a portion of the oil sample/inhibitor mixture and precipitant are mixed to provide an oil sample/inhibitor/precipitant mixture in the at least one mixing chamber (119, 619a) such that a reaction between the precipitant and the oil sample can take place which causes asphaltene to precipitate from the oil sample/inhibitor/precipitant mixture, the centrifugal force causing the oil sample/inhibitor/precipitant mixture, and the precipitated asphaltene, if present, to travel radially outward from the at least one mixing chamber (119, 619a) to the analysis chamber such that precipitated asphaltene, if present, is collected and settled/deposited in the analysis chamber starting at a radially outward end of the analysis chamber; and iv) measuring the optical properties of the oil sample/inhibitor/precipitant mixture in the analysis chamber as a function of radial distance of the analysis chamber to determine the effectiveness of the mixed inhibitor, wherein the oil sample reservoir (110, 610) and the precipitant reservoir (114, 614) are fluidly coupled to the at least one mixing chamber (119, 619a), located radially outward with respect to the oil sample reservoir and the precipitant reservoir, by channels (110a, 114a; 610a, 614a), wherein the dimensions of the channels (110a, 114a; 610a, 614a) are so configured that the ratio of oil to precipitant can be controlled, in such a way that the oil is mixed in the at least one mixing chamber at a desired precipitant-to-oil ratio under the influence of centrifugal force. i) providing a microfluidic device configured to rotate about an axis and an optical detection system, wherein the microfluidic device comprises an oil sample reservoir (110, 610) and a precipitant reservoir (114, 614) integral to the microfluidic device, at least one mixing chamber (119, 619a) integral to the microfluidic device and in fluid communication with the oil sample reservoir (110, 610) and the precipitant reservoir (114, 614), and an analysis chamber integral to the microfluidic device and in fluid communication with the at least one mixing chamber (119, 619a), and wherein the optical detection system is configured to measure optical properties of fluid in the analysis chamber; ii) filling the oil sample reservoir (110, 610) and the precipitant reservoir (114, 614), respectively, with an oil sample/inhibitor mixture and a precipitant; iii) rotating the micro fluidic device to generate centrifugal force to cause at least a portion of the oil sample/inhibitor mixture and precipitant to travel radially outward from the oil sample reservoir (110, 610) and the precipitant reservoir (114, 614) into the at least one mixing chamber (119, 619a) in which the at least a portion of the oil sample/inhibitor mixture and precipitant are mixed to provide an oil sample/inhibitor/precipitant mixture in the at least one mixing chamber (119, 619a) such that a reaction between the precipitant and the oil sample can take place which causes asphaltene to precipitate from the oil sample/inhibitor/precipitant mixture, the centrifugal force causing the oil sample/inhibitor/precipitant mixture, and the precipitated asphaltene, if present, to travel radially outward from the at least one mixing chamber (119, 619a) to the analysis chamber such that precipitated asphaltene, if present, is collected and settled/deposited in the analysis chamber starting at a radially outward end of the analysis chamber; and iv) measuring the optical properties of the oil sample/inhibitor/precipitant mixture in the analysis chamber as a function of radial distance of the analysis chamber to determine the effectiveness of the mixed inhibitor, wherein the oil sample reservoir (110, 610) and the precipitant reservoir (114, 614) are fluidly coupled to the at least one mixing chamber (119, 619a), located radially outward with respect to the oil sample reservoir and the precipitant reservoir, by channels (110a, 114a; 610a, 614a), wherein the dimensions of the channels (110a, 114a; 610a, 614a) are so configured that the ratio of oil to precipitant can be controlled, in such a way that the oil is mixed in the at least one mixing chamber at a desired precipitant-to-oil ratio under the influence of centrifugal force.