Artificial Intelligence Aided Design of Microtextured Surfaces: Application to Controlling Wettability.

Artificial intelligence (AI) has emerged as a powerful set of tools for engineering innovative materials. However, the AI-aided design of materials textures has not yet been researched in depth. In order to explore the potentials of AI for discovering innovative biointerfaces and engineering materials surfaces, especially for biomedical applications, this study focuses on the control of wettability through design-controlled hierarchical surfaces, whose design is supported and its performance predicted thanks to adequately structured and trained artificial neural networks (ANN). The authors explain the creation of a comprehensive library of microtextured surfaces with well-known wettability properties. Such a library is processed and employed for the generation and training of artificial neural networks, which can predict the actual wetting performance of new design biointerfaces. The present research demonstrates that AI can importantly support the engineering of innovative hierarchical or multiscale surfaces when complex-to-model properties and phenomena, such as wettability and wetting, are involved.

Soft-Lithography of Polyacrylamide Hydrogels Using Microstructured Templates: Towards Controlled Cell Populations on Biointerfaces.

Polyacrylamide hydrogels are interesting materials for studying cells and cell-material interactions, thanks to the possibility of precisely adjusting their stiffness, shear modulus and porosity during synthesis, and to the feasibility of processing and manufacturing them towards structures and devices with controlled morphology and topography. In this study a novel approach, related to the processing of polyacrylamide hydrogels using soft-lithography and employing microstructured templates, is presented. The main novelty relies on the design and manufacturing processes used for achieving the microstructured templates, which are transferred by soft-lithography, with remarkable level of detail, to the polyacrylamide hydrogels. The conceived process is demonstrated by patterning polyacrylamide substrates with a set of vascular-like and parenchymal-like textures, for controlling cell populations. Final culture of amoeboid cells, whose dynamics is affected by the polyacrylamide patterns, provides a preliminary validation of the described strategy and helps to discuss its potentials.

Synergies between Surface Microstructuring and Molecular Nanopatterning for Controlling Cell Populations on Polymeric Biointerfaces.

Polymeric biointerfaces are already being used extensively in a wide set of biomedical devices and systems. The possibility of controlling cell populations on biointerfaces may be essential for connecting biological systems to synthetic materials and for researching relevant interactions between life and matter. In this study, we present and analyze synergies between an innovative approach for surface microstructuring and a molecular nanopatterning procedure of recent development. The combined set of techniques used may be instrumental for the development of a new generation of functional polymeric biointerfaces. Eukaryotic cell cultures placed upon the biointerfaces developed, both before and after molecular patterning, help to validate the proposal and to discuss the synergies between the surface microstructuring and molecular nanopatterning techniques described in the study. Their potential role in the production of versatile polymeric biointerfaces for lab- and organ-on-a-chip biodevices and towards more complex and biomimetic co-culture systems and cell cultivation set-ups are also examined.

Configurable Resistive Response in BaTiO3 Ferroelectric Memristors via Electron Beam Radiation.

Ferroelectric oxide memristors are currently in the highlights of a thriving area of research aiming at the development of nonvolatile, adaptive memories for applications in neuromorphic computing. However, to date a precise control of synapse-like functionalities by adjusting the interplay between ferroelectric polarization and resistive switching processes is still an ongoing challenge. Here, it is shown that by means of controlled electron beam radiation, a prototypical ferroelectric film of BaTiO3 can be turned into a memristor with multiple configurable resistance states. Ex situ and in situ analyses of current/voltage characteristics upon electron beam exposure confirm the quasi-continuous variation of BaTiO3 resistance up to two orders of magnitude under the typical experimental conditions employed in electron beam patterning and characterization techniques. These results demonstrate an unprecedented effective route to locally and scalably engineering multilevel ferroelectric memristors via application of moderate electron beam radiation.

Lotus-on-chip: computer-aided design and 3D direct laser writing of bioinspired surfaces for controlling the wettability of materials and devices.

In this study we present the combination of a math-based design strategy with direct laser writing as high-precision technology for promoting solid free-form fabrication of multi-scale biomimetic surfaces. Results show a remarkable control of surface topography and wettability properties. Different examples of surfaces inspired on the lotus leaf, which to our knowledge are obtained for the first time following a computer-aided design with this degree of precision, are presented. Design and manufacturing strategies towards microfluidic systems whose fluid driving capabilities are obtained just by promoting a design-controlled wettability of their surfaces, are also discussed and illustrated by means of conceptual proofs. According to our experience, the synergies between the presented computer-aided design strategy and the capabilities of direct laser writing, supported by innovative writing strategies to promote final size while maintaining high precision, constitute a relevant step forward towards materials and devices with design-controlled multi-scale and micro-structured surfaces for advanced functionalities. To our knowledge, the surface geometry of the lotus leaf, which has relevant industrial applications thanks to its hydrophobic and self-cleaning behavior, has not yet been adequately modeled and manufactured in an additive way with the degree of precision that we present here.

Freeform three-dimensional embedded polymer waveguides enabled by external-diffusion assisted two-photon lithography.

This paper introduces a unique method to fabricate free-form symmetrical three-dimensional single-mode waveguides embedded in a newly developed photopolymer. The fabrication process requires only one layer of a single material by combining two-photon lithography and external monomer diffusion resulting in a high refractive index contrast of 0.013. The cured material exhibits high chemical and thermal stability. Transmission loss of 0.37 dB/cm at 850 nm is achieved. Due to the fact that waveguide arrays are produced with high density, this technique could pave the way for three-dimensional optical interconnects at the board level with high complexity and bandwidth density.

Rapid prototyping of multi-scale biomedical microdevices by combining additive manufacturing technologies.

The possibility of designing and manufacturing biomedical microdevices with multiple length-scale geometries can help to promote special interactions both with their environment and with surrounding biological systems. These interactions aim to enhance biocompatibility and overall performance by using biomimetic approaches. In this paper, we present a design and manufacturing procedure for obtaining multi-scale biomedical microsystems based on the combination of two additive manufacturing processes: a conventional laser writer to manufacture the overall device structure, and a direct-laser writer based on two-photon polymerization to yield finer details. The process excels for its versatility, accuracy and manufacturing speed and allows for the manufacture of microsystems and implants with overall sizes up to several millimeters and with details down to sub-micrometric structures. As an application example we have focused on manufacturing a biomedical microsystem to analyze the impact of microtextured surfaces on cell motility. This process yielded a relevant increase in precision and manufacturing speed when compared with more conventional rapid prototyping procedures.

High-strength cellular ceramic composites with 3D microarchitecture.

To enhance the strength-to-weight ratio of a material, one may try to either improve the strength or lower the density, or both. The lightest solid materials have a density in the range of 1,000 kg/m(3); only cellular materials, such as technical foams, can reach considerably lower values. However, compared with corresponding bulk materials, their specific strength generally is significantly lower. Cellular topologies may be divided into bending- and stretching-dominated ones. Technical foams are structured randomly and behave in a bending-dominated way, which is less weight efficient, with respect to strength, than stretching-dominated behavior, such as in regular braced frameworks. Cancellous bone and other natural cellular solids have an optimized architecture. Their basic material is structured hierarchically and consists of nanometer-size elements, providing a benefit from size effects in the material strength. Designing cellular materials with a specific microarchitecture would allow one to exploit the structural advantages of stretching-dominated constructions as well as size-dependent strengthening effects. In this paper, we demonstrate that such materials may be fabricated. Applying 3D laser lithography, we produced and characterized micro-truss and -shell structures made from alumina-polymer composite. Size-dependent strengthening of alumina shells has been observed, particularly when applied with a characteristic thickness below 100 nm. The presented artificial cellular materials reach compressive strengths up to 280 MPa with densities well below 1,000 kg/m(3).

Four-in-one interferometer for coherent and self-coherent detection.

A compact micro-optical interferometer is presented that combines two optical 90° hybrids or, alternatively, four delay interferometers into one interferometer structure sharing one tunable delay line. The interferometer can function as a frontend of either a coherent receiver or of a self-coherent receiver by adjusting the waveplates and the delay line. We built a prototype on a LIGA bench. We characterized the device and demonstrated its functionality by successful reception of a 112 Gbit/s signal.