Low-Cost Microplate Reader with 3D Printed Parts for under 500 USD

Abstract

A 96-well microplate reader for absorption spectroscopy was designed, constructed, and tested at a total cost of ca. 500 USD. The reduced cost of the device represents the major technical contribution of this manuscript, as costs were reduced 7 fold from previous reports. The device was able to achieve 3σ limits of detection of ca. 0.01 absorbance units (AU) over a 60 second measurement for the mid-visible wavelength range. Component parts are either commercially available, or 3D printed from plans. Analysis wavelength can be altered throughout the visible region through use of various photographic or theatrical filters. This feature allows the well plate reader to be used for typical laboratory assays such as cell population estimation by optical density (OD) at 600 nm, or enzyme-linked immunosorbent assays (ELISA) at 450 nm. This manuscript reports on the motivation and process of constructing the device, lists required parts, presents data demonstrating device function, and provides the community of scholars with plans to reproduce the work. The device can be reproduced in laboratories lacking sufficient resources to purchase commercially available options and this outcome contributes towards empowerment of individuals and equity of scientific enquiry.

Keywords: 3D printing; 96-well plate; additive manufacturing; low-cost science; open access; open source.

Figure 1

(A) Plate reader on lab bench prior to use. (B) Plate reader with top removed and no color filter.

Figure 2

Portion of plate reader code written in LabView. (Top) Front panel user interface. (Bottom) Block diagram.

Figure 3

(A) Plot of illumination spectra from the LED panel when using the blue, green and red filter. (B) Plot of fraction of maximal illumination vs. intensity setting set by end-user.

Figure 4

Plots of plate reader photodiode linear response for blue, green, and red channels. Each data point represents a single channel/sensor. It should be noted that ellipses viewed are each clusters of 96 individual data points. Accepted value of illumination intensity was obtained with commercially available spectrometer.

Figure 5

(A) Beer’s law plot of absorbance vs. molarity for several concentrations of crystal violet dye as measured with the plate reader and green filter. (B) Plot of measured absorbance vs. time for bleaching reaction of crystal violet dye with sodium hydroxide. For both plots, a single data point represents one measurement from a single well of the microplate.