Study of the effect of dynamic viscosity on the performance of a portable microinjector for severe dry eye treatment using a glycerol-water mixture as a test fluid

Abstract

This article presents the experimental results of a series of performance tests performed on a microinjector designed to deliver different artificial tear solutions to patients with severe dry eye syndrome. The device is intended to aid in the treatment of this syndrome by providing a continuous injection of artificial tears as needed that overcomes many of the deficiencies inherent in dripping from the manual method. In this work, a set of experiments were carried out to quantify the temporal error that allow determining the dynamic behavior of the viscosity of the glycerol/water mixture as a suitable test solution for the device and then comparing it with the use of commercial artificial tears to define an acceptable viscosity range with a lower temporal error for the correct operation of the system. The experimental method of viscosity measurement was used by means of an Ostwald viscometer that allows determining the times that flow the volume of various percentages by volume of glycerol/water and drops. In addition, the gravimetric density method was used to determine the density and subsequently by the Poiseuille relationship with respect to the densities of percentages in volume of glycerol/water and drops, the different times that flow through a capillary tube, the dynamic viscosity. The results obtained during the operation of the tested microinjector suggest that the microinjector can function correctly without problem in a range of evaluated dynamic viscosity of 1 to 1500 mP a.s with a maximum temporal error of ∼5 %. The temporal error evaluated is a parameter that is necessary to know for the well-being of patients using this device and the viscosities of the products used do not significantly influence the performance of the microinjector.