Hollow-Channel Paper Analytical Devices

Abstract

We present a microfluidic paper analytical device (μPAD) that relies on flow in hollow channels, rather than through a cellulose network, to transport fluids. The flow rate in hollow channels is 7 times higher than in regular paper channels and can be conveniently controlled from 0 to several mm/s by balancing capillary and pressure forces. More importantly, the pressure of a single drop of liquid (~0.2 mbar) is sufficient to induce fast pressure-driven flow, making hollow channels suitable for point of care diagnostics. We demonstrate their utility for simple colorimetric glucose and BSA assays in which the time for liquid transport is reduced by a factor of 4 compared to normal cellulose channels.

Rapid evaporation-driven chemical pre-concentration and separation on paper

“…Equation 5 must then generally be solved numerically. However, in the absence of evaporation, it is simple to show 7 that this leads to a steady state capillary rise height H C = P C /ρg, allowing P C to be determined experimentally from a measurement of H C .…”

“…Flow is driven by capillary action, channels have been defined using wax patterning, ink-jet printing, toner printing and boundary shaping [3][4][5][6], and devices have been fabricated with hollow and closed channels [7,8]. Detection has mainly been carried out using colorimetric assays for off-site analysis via the ubiquitous smartphone [9,10]; however, electrochemical detection has also been investigated [11,12].…”

Experimental and numerical studies on liquid wicking into filter papers for paper-based diagnostics

“…Schilling et al [10] designed a fully enclosed paper-based devices and found that the amount of toner used to enclose channels could vary the liquid flow rate. Additionally, water solube pullulan films could serve as a controlled time shutoff system, through which a paper-based device with a time-dependent sequential release of reagents could be made [11] and a hollow channel applied in paper-based devices would enhance the flow rate of solution and reduce the analysis time [12]. However, the above researches just described the qualitative tendency of liquid flow in their devices, most of them might be affected by the evaporation in an open environment.…”

Paper‐Based Inkjet‐Printed Microfluidic Analytical Devices

“…Figure 6 gives an overview of various channel fabrication principles. In the simplest case, patterning can be achieved by cutting the paper [60][61][62] (Figure 6 a), which is not further discussed here. A more widely used approach is treatment with a hydrophobic material (Figure 6 b).…”