Chiro-plasmonic refractory metamaterial with titanium nitride (TiN) core-shell nanohelices

A Survey of Recent Developments in Magnetic Microrobots for Micro-/Nano-Manipulation

Magnetically actuated microrobots have become a research hotspot in recent years due to their tiny size, untethered control, and rapid response capability. Moreover, an increasing number of researchers are applying them for micro-/nano-manipulation in the biomedical field. This survey provides a comprehensive overview of the recent developments in magnetic microrobots, focusing on materials, propulsion mechanisms, design strategies, fabrication techniques, and diverse micro-/nano-manipulation applications. The exploration of magnetic materials, biosafety considerations, and propulsion methods serves as a foundation for the diverse designs discussed in this review. The paper delves into the design categories, encompassing helical, surface, ciliary, scaffold, and biohybrid microrobots, with each demonstrating unique capabilities. Furthermore, various fabrication techniques, including direct laser writing, glancing angle deposition, biotemplating synthesis, template-assisted electrochemical deposition, and magnetic self-assembly, are examined owing to their contributions to the realization of magnetic microrobots. The potential impact of magnetic microrobots across multidisciplinary domains is presented through various application areas, such as drug delivery, minimally invasive surgery, cell manipulation, and environmental remediation. This review highlights a comprehensive summary of the current challenges, hurdles to overcome, and future directions in magnetic microrobot research across different fields.

Plasmonic Nanostructure Engineering with Shadow Growth

Physical shadow growth is a vacuum deposition technique that permits a wide variety of 3D-shaped nanoparticles and structures to be fabricated from a large library of materials. Recent advances in the control of the shadow effect at the nanoscale expand the scope of nanomaterials from spherical nanoparticles to complex 3D shaped hybrid nanoparticles and structures. In particular, plasmonically active nanomaterials can be engineered in their shape and material composition so that they exhibit unique physical and chemical properties. Here, the recent progress in the development of shadow growth techniques to realize hybrid plasmonic nanomaterials is discussed. The review describes how fabrication permits the material response to be engineered and highlights novel functions. Potential fields of application with a focus on photonic devices, biomedical, and chiral spectroscopic applications are discussed.

Review on 3D growth engineering and integration of nanowires for advanced nanoelectronics and sensor applications

Recent years have witnessed increasing efforts devoted to the growth, assembly and integration of quasi-one dimensional (1D) nanowires (NWs), as fundamental building blocks in advanced three-dimensional (3D) architecture, to explore a series of novel nanoelectronic and sensor applications. An important motivation behind is to boost the integration density of the electronic devices by stacking more functional units in theout-of-plane z-direction, where the NWs are supposed to be patterned or grown as vertically standing or laterally stacked channels to minimize their footprint area. The other driving force is derived from the unique possibility of engineering the 1D NWs into more complex, as well as more functional, 3D nanostructures, such as helical springs and kinked probes, which are ideal nanostructures for developping advanced nanoelectromechanical system (NEMS), bio-sensing and manipulation applications. This Review will first examine the recent progresses made in the construction of 3D nano electronic devices, as well as the new fabrication and growth technologies established to enable an efficient 3D integration of the vertically standing or laterally stacked NW channels. Then, the different approaches to produce and tailor more sophisticated 3D helical springs or purposely-designed nanoprobes will be revisited, together with their applications in NEMS resonators, bio sensors and stimulators in neural system.

Design, fabrication and application of magnetically actuated micro/nanorobots: a review

Magnetically actuated micro/nanorobots are typical micro- and nanoscale artificial devices with favorable attributes of quick response, remote and contactless control, harmless human-machine interaction and high economic efficiency. Under external magnetic actuation strategies, they are capable of achieving elaborate manipulation and navigation in extreme biomedical environments. This review focuses on state-of-the-art progresses in design strategies, fabrication techniques and applications of magnetically actuated micro/nanorobots. Firstly, recent advances of various robot designs, including helical robots, surface walkers, ciliary robots, scaffold robots and biohybrid robots, are discussed separately. Secondly, the main progresses of common fabrication techniques are respectively introduced, and application achievements on these robots in targeted drug delivery, minimally invasive surgery and cell manipulation are also presented. Finally, a short summary is made, and the current challenges and future work for magnetically actuated micro/nanorobots are discussed.

Chiro-optical response of a wafer scale metamaterial with ellipsoidal metal nanoparticles

We report a large chiro-optical response from a nanostructured film of aperiodic dielectric helices decorated with ellipsoidal metal nanoparticles. The influence of the inherent fabrication variation on the chiro-optical response of the wafer-scalable nanostructured film is investigated using a computational model which closely mimics the material system. From the computational approach, we found that the chiro-optical signal is strongly dependent on the ellipticities of the metal nanoparticles and the developed computational model can account for all the variations caused by the fabrication process. We report the experimentally realized dissymmetry factor ∼1.6, which is the largest reported for wafer scalable chiro-plasmonic samples till now. The calculations incorporate strong multipolar contributions of the plasmonic interactions to the chiro-optical response from the tightly confined ellipsoidal nanoparticles, improving upon the previous studies carried in the coupled dipole approximation regime. Our analyzes confirm the large chiro-optical response in these films developed by a scalable and simple fabrication technique, indicating their applicability pertaining to manipulation of optical polarization, enantiomer selective identification and enhanced sensing and detection of chiral molecules.

Gallium chiral nanoshaping for circular polarization handling

In this work we report the local growth of ordered arrays of 3D core-shell chiral nanohelices based on plasmonic gallium metal. The structures can be engineered in a single step using focused ion beam induced deposition, where a Ga⁺ ion source is used to shape the metallic nanohelix core, while the dielectric precursor is dissociated to create dielectric shells. The solubility of gallium in the different investigated dielectric matrices controls the core-shell thickness ratio of the nanohelices. The chiral plasmonic behaviour of these gallium-based nanostructures is experimentally measured by circularly polarized light transmission through nanostructure arrays and compared with numerical simulations. Large chiroptical effects in the visible range are demonstrated due to the plasmonic effects arising from gallium nanoclusters in the core.

Focused Ion Beam Processing for 3D Chiral Photonics Nanostructures

The focused ion beam (FIB) is a powerful piece of technology which has enabled scientific and technological advances in the realization and study of micro- and nano-systems in many research areas, such as nanotechnology, material science, and the microelectronic industry. Recently, its applications have been extended to the photonics field, owing to the possibility of developing systems with complex shapes, including 3D chiral shapes. Indeed, micro-/nano-structured elements with precise geometrical features at the nanoscale can be realized by FIB processing, with sizes that can be tailored in order to tune optical responses over a broad spectral region. In this review, we give an overview of recent efforts in this field which have involved FIB processing as a nanofabrication tool for photonics applications. In particular, we focus on FIB-induced deposition and FIB milling, employed to build 3D nanostructures and metasurfaces exhibiting intrinsic chirality. We describe the fabrication strategies present in the literature and the chiro-optical behavior of the developed structures. The achieved results pave the way for the creation of novel and advanced nanophotonic devices for many fields of application, ranging from polarization control to integration in photonic circuits to subwavelength imaging.

Flagellar nanorobot with kinetic behavior investigation and 3D motion

Wirelessly controlled nanorobots have the potential to perform highly precise maneuvers within complex in vitro and in vivo environments. Flagellar nanorobots will be useful in a variety of biomedical applications, however, to date there has been little effort to investigate essential kinetic behavior changes related to the geometric properties of the nanorobot and effects imparted to it by nearby boundaries. Flagellar nanorobots are composed of an avidin-coated magnetic nanoparticle head (MH) and a single biotin-tipped repolymerized flagellum that are driven by a wirelessly generated rotating magnetic field. Nanorobots with different MHs and flagellar lengths were manually guided to perform complex swimming trajectories under both bright-field and fluorescence microscopy visualizations. The experimental results show that rotational frequency, handedness of rotation direction, MH size, flagellar length, and distance to the bottom boundary significantly affect the kinematics of the nanorobot. The results reported herein summarize fundamental research that will be used for the design specifications necessary for optimizing the application of helical nanorobotic devices for use in delivery of therapeutic and imaging agents. Additionally, robotic nanoswimmers were successfully navigated and tracked in 3D using quantitative defocusing, which will significantly improve the efficiency, function, and application of the flagellar nanorobot.