Life Cycle Assessment of microfluidic devices for point-of-care testing

Abstract

In microfluidics, typical laboratory processes can be condensed to a miniature device. This reduces analysis time and required volumes of samples and reagents, increases mobility and flexibility, and is cost effective. In this work, the environmental impacts of three microfluidic devices for glucose detection are assessed using a comparative life cycle assessment (LCA) from cradle-to-grave. The three devices are a polydimethylsiloxane (PDMS) device manufactured through soft lithography, a paper device manufactured through wax stamping, and a polylactic acid (PLA) device manufactured through 3D printing. The environmental impacts are determined for two manufacturing scenarios: on laboratory-scale and commercial-scale. The functional unit is 1 act of glucose detection performed on a human sample using 1 microfluidic glucose detection device.
Assuming laboratory-scale manufacturing, the paper device has the lowest environmental impacts, whereas the PLA device has the highest impact. The main contributing processes are those pertaining to the devices' manufacture. For the PDMS device, these are the processes for soft lithography, for the paper device it is the paraffin use, while for the PLA device it is the 3D printing. Assuming commercial-scale manufacturing, the PLA device has the lowest environmental impact, whereas the PDMS device has the highest impact. This scenario was modelled by improving efficiencies in the manufacturing of the PDMS and paper device, and substituting 3D printing for injection moulding for the PLA device.
To reduce the devices' environmental impacts, a general recommendation is to transition to an electricity mix based on renewables rather than fossil fuels. For the PDMS device, a recommendation is to redesign the device such that the user can apply reagents before use, thereby avoiding emissions by cutting out a need for refrigeration, which is present in the current design. For the paper device a recommendation is to minimise the waste of paraffin, as it is the main contributor to the device's environmental impacts. Lastly, for the paper and PLA device it is recommended to consider alternate manufacturing methods when upscaling production. Their current manufacturing methods are ideal for prototyping, but are inefficient on a commercial scale.
Some limitations are that several data points were estimated, cut off, or secondary. Data gaps were bridged through the use of proxies and stoichiometry for chemicals, which affected the accuracy of the model. Furthermore, recycling and chance of failure during manufacture are not accounted for. Lastly, as microfluidic devices are designed in many different ways, the results cannot be translated one-to-one to other devices. They can only provide a general idea of what the impacts for other devices might be.
A continuation of this work could simulate the synthesis of chemicals using process design software, for increased accuracy. Another opportunity for further study is to collect and implement primary data and assess how that affects the results. Future research could investigate fields of microfluidics other than diagnostics. Generally, more research is necessary to model a proper ex-ante LCA with various scenarios. With enough research, microfluidics might fully reach its potential, while being environmentally responsible.