A handheld orbital mixer for processing viscous samples in low resource settings

Clinical diagnostics play an important role in infectious disease monitoring. Often these diseases are endemic in settings that lack laboratory resources, which limits the types of tools that are available. Mixing is a common procedure in clinical diagnostic assays and is not immune to these challenges. In this report, we characterize the efficacy of a handheld therapeutic massager that has been repurposed into a mixer. Using metal affinity functionalized magnetic beads and a histidine-tagged fluorescent label, we find that this inexpensive orbital mixer is effective over a range of clinically relevant sample volumes and viscosities. Even with larger sample volumes (> 200 mu L) and more viscous sample matrices (3 x eta H2O), the mixer binds more than 90% of the biomarkers in solution in less than 90 seconds. In a clinical assay for the detection of Plasmodium falciparum histidine-rich protein 2, we find there is no statistical difference in performance between our inexpensive and portable orbital mixer and a standard laboratory benchtop vortexer.