A versatile capillaric microfluidics viscometer platform for bar-graph type point-of-care diagnostics

Abstract

A novel capillary action microfluidic viscometer has been designed that can measure the relative viscosity of a sample compared to a control liquid. Using capillary action circuits, the viscosity of a sample is transformed into a microfluidic bar-graph format without the use of external instrumentation. The bars in this case are represented by the distance that a liquid has flown through a microfluidic channel, relative to another liquid in an identical channel. As the device does not require external instrumentation, its use is targeted at point-of-care (PoC) situations. This implementation is made practical through capillaric Field Effect Transistors, and the conditional flow paths they enable. In this paper, we report on the design, operation, and performance of a two-channel version viscometer device exclusively based on capillary action circuits. Using poly-ethylene glycol solutions as viscous samples, we demonstrate that the device can transduce the relative viscosity consistently to within 2%. Enabled by the flexibility of the capillary action circuits, we additionally present a modified device which can measure transparent liquids without the need to add colorants to the sample. The forms of the device presented in this work have applications in both medical care and scientific measurements—particularly for PoC measurements.

Capillary-driven microfluidics: impacts of 3D manufacturing on bioanalytical devices

“…7a). Although this valve was utilized within a microfluidic device to measure a relative viscosity, 49 it has the potential to be applied for bioanalytical assays. Moreover, in a recent study, we introduced a pre-programmed capillary-driven microfluidic device, in which a π-valve array was integrated in a capillary circuit for the sequence release of 3 different liquids.…”

Field Effect Transistor-Like Control of Capillaric Flow Using Off-Valves

“…Test devices used in this work were fabricated from cross-linked polymethylmethacrylate (PMMA; 4.5 mm general purpose acrylic; PSP Plastics) as previously described [8,9]. Channel milling was performed using a Mini-Mill/GX micro milling machine running a NSK-3000 Spindle (Minitech Machinery Corporation), with a minimum addressable step size of 1 µm.…”

“…Once the bubble completely occludes the channel, further fluid flow in it is near completely restricted. This concept has been used to successfully demonstrate a range of practical microfluidic operations, and proof-of-concept viscometry assay [8].…”