Innovative 3D-printed analytical device for heavy metals analysis with smartphone detection – SMART-3D

Contamination of aquatic environments by heavy metals is a major concern in the scientific community and for societal issues. Indeed, these pollutants are generally not biodegradable and can accumulate in the environment. Among these heavy metals, lead, cadmium and mercury have attracted most attention due to toxicity issues. Regulatory organisms have strictly defined the concentration limits of these three heavy metals in various types of waters, including drinking water and surface waters. Mobile and portable devices would therefore be a precious tool for on-site analysis of these heavy metals, enabling rapid evaluation of the contamination of water samples.
The objective of the proposed project is to develop an analytical device for lead, cadmium and mercury (concentration of free ions and ions complexed to organic matter), which will be designed as a potentially portable and suitable tool for on-site application (development up to Technology Readiness Level 4, laboratory validation). High selectivity and sensitivity will be required in order to allow the analysis of targeted water samples (drinking water or surface waters) with quantification limits below 1 µg L-1 and low interferences (<5%) from other cations or naturally occurring compounds. Several innovations will enable to reach the desired features of our device:
Selectivity and sensitivity will mainly stem from the design of fluoroionophores bearing specific electron donating groups (oxygen, sulfur, nitrogen) to provide high affinity for heavy metals. Design of three selective fluoroionophores (one for each targeted metal) based on the same fluorogenic part (in order to have a common optical detection system for the three metals) will be the main challenge of the first part of the work.
Fluorescent sensors will be grafted on a 3D-printed microfluidic unit which will be used as a preconcentration module in order to improve sensitivity of conventional liquid-phase fluorescent sensing. Current scientific obstacle for the direct fluorescence reading on a 3D-printed solid surface lies in the very high fluorescence of commercial 3D printing resin, which is due to the resin composition (mainly photoinitiators). Smart formulation of photosensitive 3D printing resins with very low background fluorescence and potential for molecular sensors grafting will be required in order to subsequently print preconcentration units with the adequate fluorescent sensing properties after grafting the fluorescent sensors.
Detection and quantification of the fluorescence generated by the presence of metal cations will be then performed thanks to the sensors included in smartphones. Smartphones are indeed portable, widely available, affordable, user-friendly, and therefore well suited to act as an effective platform for on-site detection The targeted optical device will use the camera of a smartphone for light measurements and a dedicated and specially developed application for quantification.
Finally, on-site determination of global metal concentrations (including ions complexed to organic matter) will be performed by the design of a portable photo-oxidation microfluidic module which will be used to pretreat the sample before analysis with the previously described device. The scientific challenge of this task will be the development of a portable photo-oxidation module, battery-powered with low tensions power supply (12-24V) but powerful enough to breakdown organic matter in a reasonable time.
The final product will include the 3D-printed preconcentration modules grafted with the fluorescent sensors, the optical system for smartphone detection, the portable photo-oxidation module and a set of small peristaltic pumps (for fluids propulsion) controlled by a portable electronic interface. All these components will be integrated together to provide a portable laboratory prototype which can be validated on real samples.