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Autonomous Paper-based Point-of-Care Biosensing System

Final Report Summary - APPOCS (Autonomous Paper-based Point-of-Care Biosensing System)

Autonomous Paper-based Point-of-Care Biosensing System (APPOCS)
The objective of this project was the development of paper-based fuel cells, batteries and redox flow batteries to power point-of-care analytical devices. The devices would comprise a power source, biosensors, electronics module and display, to allow the autonomous quantitative measurement of a biological sample and visualize the results within a thin, flexible and disposable package. A first phase of the project, the outgoing period at the University of Washington in Seattle, was dedicated to acquiring the skills and methodology to develop paper-based microfluidic devices such as fuel cells and biosensors. The second phase, return period at Instituto de Microelectrónica de Barcelona IMB-CNM (CSIC), was dedicated to transfer these skills into the host organization and integrate the paper-based power sources and biosensors with the proper electronics and display on a flexible substrate. The outcome of the project will be a functional working prototype transferable to the manufacturing technology used in organic electronics (OE).
The development of microfluidic fuel cells on paper is one the key results from this project. The devices take advantage of the capillarity in a paper matrix to eliminate the need of external pumps to establish the flow of reactants. Furthermore, the design has been inspired in the simplicity and convenience of standard lateral flow test strips, which makes it suitable for manufacturing using the same mass production methods. This work sets the basis for the development of autonomous diagnostic devices that could be powered from the same biological sample to be analyzed (e.g. using glucose in blood or urea in urine).
A second highlight of this period is the development of paper-based hydrogen fuel cells, taking advantage of the by-product of an exothermic reaction used for nucleic acid amplification in point-of-care devices. This concept has the potential to fulfill the power requirements of many portable diagnostic devices while having less of a negative environmental impact than other power sources (like lithium-ion batteries) and staying within the cost margins of disposable point-of-care devices. The first prototype was designed with the same form factor and power requirements of an existing commercially successful device, such as pregnancy and ovulation tests. This demonstrated that the technology is particularly well-suited to make quantitative next generation point-of-care tests in the absence of peripheral equipment or power sources.
Following the same simplicity and ease of use achieved with the paper microfluidic fuel cells, paper-based batteries were designed and fabricated. These batteries are mainly composed of paper, carbon and non-toxic, abundant and inexpensive metals as electrodes. Contrary to a fuel cell, the battery does not need a specific fuel to provide electric energy. It can be activated by the addition of any liquid, even plain water. One of the most relevant outcomes of the project has been the creation of the startup company Fuelium, which will commercialize this paper-based battery technology. The batteries provide an environmentally friendly alternative to substitute Li-ion coin cell batteries in disposable point-of-care applications. The paper-based batteries can be fabricated in the same cost-effective roll-to-roll technology currently used by lateral flow test industry. They are activated upon the addition of a liquid sample, they are able to work with water as well as with most relevant biological matrices in point-of-care applications (blood, urine and saliva).
Especially remarkable was the development of biodegradable redox batteries, introducing the first battery that is truly biodegradable under biotic conditions, which can potentially eliminate the end-of-life concerns posed by current primary battery technologies. The device was conceived to be discarded without the need of any specific recycling facilities after its usage because of its all-organic nature, causing no harm to the environment where it is disposed. This was achieved by selecting non-toxic, organic, abundant and inexpensive raw materials for its fabrication and using cost-efficient scalable manufacturing processes. This technology changes the unsustainable portable battery paradigm, from considering it a harmful waste to a source of materials that can nurture the environment, enrich soil or remove toxins from water beyond the ordinary life cycle of a battery.
During the return period at the host organization the objective was designing and testing all the different components to be integrated in a complete point-of-care analysis system. As a first step into printed electronics technologies, the implementation of screen-printing and inkjet printing processes was done at the host organization. This was used to fabricate conductive tracks and electrodes for electrochemical sensors and power sources. Electrochromic displays were designed and custom-made in collaboration with an external company. The performance specifications of the electronic modules were defined, which will take the energy from the paper-based power sources to measure the signal from the sensors and show the results in the display.
The practical utility of the different paper-based power sources developed during this project was demonstrated by direct substitution of a lithium ion coin cell in commercial analytical devices. The paper-based hydrogen fuel cell and batteries were used in a typical point-of-care diagnostic application, i.e. an optoelectronic reader of lateral flow assays. In the other hand, the biodegradable paper-based redox battery was used to power a portable environmental sensor that monitors different parameters in water, such as conductivity, total dissolved solids and temperature.
This project sets the guidelines to obtain a fully autonomous analytical device by providing an onboard energy source and the proper instrumentation to perform the measurement and visualize the result. The implementation of printed and organic electronics technology implies that the devices would be extremely portable and would not require any additional instrument to view the analysis result.
An overview of the project objectives and results can be seen at www.speedresearchgroup.com.
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