Mix-Bricks and Flip-Lids: 3D Printed Devices for Simple, Simultaneous Mixing of Reactant Solutions I. Design, Use, and Application to the Quantification of Ascorbic Acid by an Iodine Clock Reaction.

Two types of 3D printed devices for simultaneous mixing of small volumes (e.g., 50-500 µL) of reactant solutions are described. One device (a "Flip-Lid") is a specially designed lid for commercially available 96-well plates, with which solutions in adjacent wells can be mixed by inversion. The other type ("Mix-Bricks") consists of two 3D printed parts: an interlocking "brick" that contains a selected number of wells of specified volume, and a lid for mixing solutions in adjacent wells by inversion. In both cases, the lids contain transparent windows through which reactions can be visually monitored or recorded. The application of these devices to quantitative measurements was evaluated by use of an iodine clock reaction to quantify ascorbic acid in fruit juices and vitamin C tablets. A smartphone camera was used to record the times at which color appeared as a function of ascorbic acid concentration, producing a linear calibration curve with time as the dependent variable. Up to twelve reactions, each involving four reactant solutions, were monitored simultaneously in a single device. Replicate measurements within a given device consistently yielded standard deviations of less than 5% RSD. Accuracy was evaluated by comparison of vitamin C tablet results to those obtained by iodine titration and by HPLC-UV; all three methods were within 1.3% of the overall mean of 543 mg/tablet. These 3D printed devices thus show promise for simultaneous reaction monitoring in a wide variety of applications.