4D Printing of Plasmon-Encoded Lenses on Nanostructured Porous Silicon for in-Field Fluorescence Microscopy of Microbes

Barillaro, Giuseppe

Here we report the 4D printing of a magnifying polydimethylsiloxane (PDMS) lens encoded with a tunable plasmonic rejection filter [1]. The lens is formed by moldless printing of PDMS pre-polymer on a nanostructured porous silicon (PSi) templating layer [2]. A nanometer-thick plasmonic filter is integrated on the lens surface by in situ synthesis of Ag and Au nanoparticles (NPs) with programmed density [3]. The filter can be designed to reject light at the plasmonic resonance wavelength of the NPs with an optical density tun- able from 0 to 3 and retreive light at longer wavelengths with a pass-to-stop band ratio tunable from 0 to 60 dB. Swelling of PDMS in hexane and ether is used to change the NP density on the lens surface and modulate, in turn, the transmittance properties of the NP-decorated lens over 3 orders of magnitude. The plasmon-encoded lens is coupled to a commercial smartphone demonstrating: shaping of the emission spectrum of a white light-emitting diode to tune the color from yellow to purple; real-time bright-field and fluorescence microscopy of living microbes in water, namely, the auto-fluorescent green alga Chlorogonium sp. and the ciliated protozoan Euplotes daidaleos.

The proposed 4D printing approach of NP-decorated PDMS lenses is immediately extendable to other metal nanoparticles, besides Ag and Au NPs, which can be also co-synthetized on the lens surface; the shape of NPs on the lens can be engineered to tune the plasmonic filter characteristics, such as reso- nance wavelength and quality factor; further, dynamic tuning of the pre-designed optical properties of the PDMS lens (i.e., focal length, magnification) and NP filter (i.e., wavelength, transmittance) can be performed by exposure to different solvents, besides hexane and diethyl ether.

We foresee the use of the proposed 4D printed NP-decorated PDMS lenses for a variety of lighting applications, such as color tuning, light filtering, and on-field microscopy applications, among which bacteria and pathogen detection on wounds, surface, and food, as well as water quality monitoring through protozoa and protists identification and quantification.

References

[1] S. Mariani, M. Corsi, A. Paghi, A. A. La Mattina, L. Strambini, F. P. Frontini, G. Di Giuseppe, G. Barillaro, Adv. Optical Mater. 2021, 2101610.

[2] S. Mariani, V. Robbiano, R. Iglio, A. A. La Mattina, P. Nadimi, J. Wang, B. Kim, T. Kumeria, M. J. Sailor, G. Barillaro, Adv. Funct. Mater. 2020, 30, 1906836.

[3] S. Mariani, A. Amedeo La Mattina, A. Paghi, L. Strambini, G. Barillaro, Adv. Funct. Mater. 2021, 2100774

Acknowledgments

S.M. and M.C. contributed equally to this work. G.B. acknowledges the support of Italian Ministry of Education, University and Research (MIUR) in the framework of the CrossLab project (Departments of Excellence).

1985 4D Printing of Plasmon-Encoded Lenses on Nanostructured Porous Silicon for in-Field Fluorescence Microscopy of Microbes

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4D Printing of Plasmon-Encoded Lenses on Nanostructured Porous Silicon for in-Field Fluorescence Microscopy of Microbes