Paper Microfluidic Device with a Horizontal Motion Valve and a Localized Delay for Automatic Control of a Multistep Assay

A microfluidic paper-based analytical device (mu PAD) is a cost-effective platform to implement assays, especially for point-of-care testing. Developing mu PADs with fluidic control is important to implement multistep assays and provide high sensitivities. However, current localized delays in mu PADs made of sucrose have a limited ability to decrease the flow rate. In addition, existing mu PADs for automatic multistep assays are limited by their need for auxiliary instruments, their false activation, or their unavoidable tradeoff between available fluid volumes and temporal differences between steps. Here, a novel mu PAD composed of a localized dissolvable delay and a horizontal motion mechanical valve for use as an automatic multistep assay is reported. A mixture of fructose and sucrose was used in the localized dissolvable delay and it provided an effective decrease in the flow rate to ensure adequate sensitivity in an assay. The dissolvable delay effectively doubled the flow time. A mechanical valve using a horizontal movement was developed to automatically implement a multistep process. Two-step and four-step processes were enabled with the mu PAD. Cardiac troponin I (cTnI), a gold-standard biomarker for myocardial infarction, was used as a model analyte to show the performance of the developed mu PAD in an assay. The designed mu PAD, with the simple-to-make localized dissolvable delay and the robust mechanical valve, provides the potential to automatically implement high-performance multistep assays toward a versatile platform for point-of-care diagnostics.

Automated summary

The novel mu PAD with a localized dissolvable delay and a horizontal motion mechanical valve allows for automatic implementation of high-performance multistep assays, showing great potential as a versatile platform for point-of-care diagnostics.