Optically controlled fluid flow: enabling smart paper-based medical diagnostic devices

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Access to affordable, reliable, user-friendly and rapid medical diagnostic tests has been identified by the World Health Organization (WHO) as a global imperative. In both the developed and developing world, point-of-care (POC) devices are the diagnostic tool of choice, where an answer is provided in a matter of minutes to questions that currently address the relatively straightforward conditions relating to pregnancy or diabetes. Affordable, but user-friendly testing must also be directed to other major complaints and conditions such as HIV, Hepatitis, Malaria, TB and a range of allergies. Moving beyond a simple binary yes/no result, as for a pregnancy test, to tests that provide a quantitative or semi-quantitative result is a global imperative and together with the added demands for greatly enhanced sensitivity and limit of detection are the holy-grail for the diagnostic industry. A multi-testing environment in a paper-based format, where fluid flow can be routed, delayed, gated and mixed will implement these provisions and optimize the outcome of the testing procedure. This is the aim of our novel optically-assisted gated fluid flow technology, which will usher in a much-needed transformative breakthrough that hugely expands the application-domain of fluidics-based diagnostic devices namely lateral flow devices (LFDs) and paper-based analytical devices. While paper-based fluidic devices that rely on their current passive self-wicking process can address some basic functionalities , enabling triggerable on-demand fluid flow using responsive photopolymers will provide a hugely significant step-change in their diagnostic capability through inclusion of the following features : (a) incubation of fluidic sample with a desired biochemical reagent within a channel to maximize the sensitivity and limit of detection; (b) timed on/off gating to allow dispensing of pre-determined sample volume for semi-quantitative detection; (c) triggering-on the sample flow at a desired time for controlled and user-friendly testing and (d) dynamic flow control within multiple flow channels to enable multistep reactions. Our proposal is to develop a paper platform where liquid flow can be controllably switched on and off via non-contact illumination of responsive photopolymers using low power optical addressing. Such a capability will massively transform the current passive lateral flow devices (LFDs) into true lab-on-chip type multi-functional test-beds bringing immediate and quantifiable impact within the medical diagnostic and healthcare sectors.