micromachines Review Nanopatterning with Photonic Nanojets: Review and Perspectives in Biomedical Research Salvatore Surdo 1,* , Martí Duocastella 1,2,* and Alberto Diaspro 1,3,* 1 Nanoscopy, Istituto Italiano di Tecnologia, Via Enrico Melen 83, Building B, 16152 Genoa, Italy 2 Department of Applied Physics, University of Barcelona, C/Martí i Franquès 1, 08028 Barcelona, Spain 3 Department of Physics, University of Genoa, Via Dodecaneso 33, 16146 Genova, Italy * Correspondence:
[email protected] (S.S.);
[email protected] (M.D.);
[email protected] (A.D.) Abstract: Nanostructured surfaces and devices offer astounding possibilities for biomedical re- search, including cellular and molecular biology, diagnostics, and therapeutics. However, the wide implementation of these systems is currently limited by the lack of cost-effective and easy-to-use nanopatterning tools. A promising solution is to use optical methods based on photonic nanojets, namely, needle-like beams featuring a nanometric width. In this review, we survey the physics, engi- neering strategies, and recent implementations of photonic nanojets for high-throughput generation of arbitrary nanopatterns, along with applications in optics, electronics, mechanics, and biosensing. An outlook of the potential impact of nanopatterning technologies based on photonic nanojets in several relevant biomedical areas is also provided. Keywords: nanotechnology; lithography; laser direct-write; near field; subwavelength Citation: Surdo, S.; Duocastella, M.; 1. Introduction Diaspro, A. Nanopatterning with The ability to pattern a surface with tailored nanostructures, such as trenches, pil- Photonic Nanojets: Review and lars, and spirals, has led to significant advances in the field of biomedical research [1–3]. Perspectives in Biomedical Research. Nanoscale features provide access to unique mechanical, optical, and electronic phenom- Micromachines 2021, 12, 256.