3D Micropatterned Surface Inspired by Salvinia molesta via Direct Laser Lithography

Biomimetic functional surfaces are attracting increasing attention for their relevant technological applications. Despite these efforts, inherent limitations of microfabrication techniques prevent the replication of complex hierarchical microstructures. Using a 3D laser lithography technique, we fabricated a 3D patterned surface bioinspired to Salvinia molesta leaves. The artificial hairs, with crownlike heads, were reproduced by scaling down (ca. 100 times smaller) the dimensions of natural features, so that microscale hairs with submicrometric resolution were attained. The micropatterned surface, in analogy with the natural model, shows interesting properties in terms of hydrophobicity and air retention when submerged by water, even if realized with a hydrophilic material. Furthermore, we successfully demonstrated the capability to promote localized condensation of water droplets from moisture in the atmosphere

Air Trapping Mechanism in Artificial Salvinia-Like Micro-Hairs Fabricated via Direct Laser Lithography

Salvinia leaves represent an extraordinary example of how nature found a strategy for the long term retainment of air, and thus oxygen, on a surface, the so-called ‘Salvinia effect’, thanks to the peculiar three-dimensional and hierarchical shape of the hairs covering the leaves. Here, starting from the natural model, we have microfabricated hairs inspired by those present on the Salvinia molesta leaves, by means of direct laser lithography. Artificial hairs, like their natural counterpart, are composed of a stalk and a crown-like head, and have been reproduced in the microscale since this ensures, if using a proper design, an air-retaining behavior even if the bulk structural material is hydrophilic. We have investigated the capability of air retainment inside the heads of the hairs that can last up to 100 h, demonstrating the stability of the phenomenon. For a given dimension of the head, the greater the number of filaments, the greater the amount of air that can be trapped inside the heads since the increase in the number of solid–air interfaces able to pin the liquid phase. For this reason, such type of pattern could be used for the fabrication of surfaces for controlled gas retainment and gas release in liquid phases. The range of applications would be quite large, including industrial, medical, and biological fields

Air trapping mechanism in artificial Salvinia-like micro-hairs fabricated via direct laser lithography

Salvinia leaves represent an extraordinary example of how nature found a strategy for the long term retainment of air, and thus oxygen, on a surface, the so-called 'Salvinia effect', thanks to the peculiar three-dimensional and hierarchical shape of the hairs covering the leaves. Here, starting from the natural model, we have microfabricated hairs inspired by those present on the Salvinia molesta leaves, by means of direct laser lithography. Artificial hairs, like their natural counterpart, are composed of a stalk and a crown-like head, and have been reproduced in the microscale since this ensures, if using a proper design, an air-retaining behavior even if the bulk structural material is hydrophilic. We have investigated the capability of air retainment inside the heads of the hairs that can last up to 100 h, demonstrating the stability of the phenomenon. For a given dimension of the head, the greater the number of filaments, the greater the amount of air that can be trapped inside the heads since the increase in the number of solid-air interfaces able to pin the liquid phase. For this reason, such type of pattern could be used for the fabrication of surfaces for controlled gas retainment and gas release in liquid phases. The range of applications would be quite large, including industrial, medical, and biological fields

A 3D Biohybrid Real-Scale Model of the Brain Cancer Microenvironment for Advanced In Vitro Testing

The modeling of the pathological microenvironment of the central nervous system (CNS) represents a disrupting approach for drug screening for advanced therapies against tumors and neuronal disorders. The in vitro investigations of the crossing and diffusion of drugs through the blood–brain barrier (BBB) are still not completely reliable, due to technological limits in the replication of 3D microstructures that can faithfully mimic the in vivo scenario. Here, an innovative 1:1 scale 3D-printed realistic biohybrid model of the brain tumor microenvironment, with both luminal and parenchyma compartments, is presented. The dynamically controllable microfluidic device, fabricated through two-photon lithography, enables the triple co-culture of hCMEC/D3 cells, forming the internal biohybrid endothelium of the capillaries, of astrocytes, and of magnetically-driven spheroids of U87 glioblastoma cells. Tumor spheroids are obtained from culturing glioblastoma cells inside 3D microcages loaded with superparamagnetic iron oxide nanoparticles (SPIONs). The system proves to be capable in hindering dextran diffusion through the bioinspired BBB, while allowing chemotherapy-loaded nanocarriers to cross it. The proper formation of the selective barrier and the good performance of the anti-tumor treatment demonstrate that the proposed device can be successfully exploited as a realistic in vitro model for high-throughput drug screening in CNS diseases

Novel fabrication method for highly conformable THz metasurfaces

The continuously increasing interest in flexible and integrated photonics requires new strategies for device manufacturing on arbitrary complex surfaces and with lowest possible size, respectively. Terahertz (THz) technology can particularly benefit from this approach to implement compact systems for generation, detection and on-demand manipulation of THz radiation. Here we present a novel fabrication method to realize conformable metasurfaces. The flexible and versatile character of polymeric nanomembranes is combined with direct laser writing via two-photon polymerization and metal deposition to develop freestanding ultra-thin quasi-perfect plasmonic absorbers with an unprecedentedly high level of conformability. Moreover, revealing new flexible dielectric materials presenting low absorption and permittivity in the THz range, this work paves the way for the realization of ultra-thin, conformable hybrid or all-dielectric devices enhancing the application of THz technologies, and flexible/integrated photonics in general.</p

Highly conformable terahertz metasurfaces via two-photon polymerization on polymeric ultra-thin films

The interest in flexible and integrated photonics requires new strategies for device manufacturing on arbitrary complex surfaces. THz technology can particularly benefit from this approach to implement compact systems for generation, detection, and manipulation of THz radiation. Here we present a novel fabrication method to realize conformable metasurfaces. The flexible and versatile character of polymeric nanomembranes is combined with direct laser writing and metal deposition to develop freestanding ultra-thin THz devices with an unprecedentedly high level of conformability.</p

Highly conformable terahertz metasurfaces via two-photon polymerization on polymeric ultra-thin films

The interest in flexible and integrated photonics requires new strategies for device manufacturing on arbitrary complex surfaces. THz technology can particularly benefit from this approach to implement compact systems for generation, detection, and manipulation of THz radiation. Here we present a novel fabrication method to realize conformable metasurfaces. The flexible and versatile character of polymeric nanomembranes is combined with direct laser writing and metal deposition to develop freestanding ultra-thin THz devices with an unprecedentedly high level of conformability.</p

Dry adhesion of artificial gecko setae fabricated via direct laser lithography

© Springer International Publishing AG 2017. Biomimetics has introduced a new paradigm: by constructing structures with engineered materials and geometries, innovative devices may be fabricated. According to this paradigm, both shape and material properties are equally important to determine functional performance. This idea has been applied also in the field of the microfabrication of smart surfaces, exploiting properties already worked out by nature, like in the case of self-cleaning, drag reduction, structural coloration, and dry adhesion. Regarding dry adhesive properties, geckos represent a good example from which we take inspiration, since they have the extraordinary ability to climb almost every type of surface, even smooth ones, thanks to the hierarchical conformation of the fibrillary setae in their toe pads. Due to this design, they can increase the area of contact with a surface and thus the amount of attractive van der Waals forces. While reproducing with artificial materials the same functional morphology of gecko’s pads is typically not achievable with traditional microfabrication techniques, recently Direct Laser Litography offered new opportunities to fabrication of complex three-dimensional structures in the microscale with nanometric resolution. Using direct laser lithography, we have fabricated artificial gecko setae, reproducing with unprecedented faithfulness the natural morphology in the same dimensional scale. Adhesion force of artificial setae toward different surfaces have been tested in dry condition by means of a dedicated setup and compared with natural ones

Dry adhesion of artificial gecko setae fabricated via direct laser lithography

Biomimetics has introduced a new paradigm: by constructing structures with engineered materials and geometries, innovative devices may be fabricated. According to this paradigm, both shape and material properties are equally important to determine functional performance. This idea has been applied also in the field of the microfabrication of smart surfaces, exploiting properties already worked out by nature, like in the case of self-cleaning, drag reduction, structural coloration, and dry adhesion. Regarding dry adhesive properties, geckos represent a good example from which we take inspiration, since they have the extraordinary ability to climb almost every type of surface, even smooth ones, thanks to the hierarchical conformation of the fibrillary setae in their toe pads. Due to this design, they can increase the area of contact with a surface and thus the amount of attractive van der Waals forces. While reproducing with artificial materials the same functional morphology of gecko’s pads is typically not achievable with traditional microfabrication techniques, recently Direct Laser Litography offered new opportunities to fabrication of complex three-dimensional structures in the microscale with nanometric resolution. Using direct laser lithography, we have fabricated artificial gecko setae, reproducing with unprecedented faithfulness the natural morphology in the same dimensional scale. Adhesion force of artificial setae toward different surfaces have been tested in dry condition by means of a dedicated setup and compared with natural ones