Digital Fabrication of Transparent Electrodes for Simultaneously Optical and Electrochemical Biosensor Applications

This dissertation proposes a pioneering biosensor for detecting cancer biomarkers that combines electrochemical and optical recognition in the same analyzing spot, by taking advantage of laser direct writing to pattern transparent and flexible electrodes. The bi-omarker, the carcinoembryonic antigen (CEA), is detected by an antibody-like biomi-metic material as recognizing agent. The sensing film over indium tin oxide (ITO) coated glass substrate consisted of a molecularly imprinted layer of polypyrrole (PPy). The im-printed film is assembled on a three-dimensional photonic crystal composed of silica na-noparticles (NPs), allowing optical detection. The molecularly imprinted polymer was obtained through electropolymerization of pyrrole in the presence of the biomarker as template. The interaction between the biomarker and the sensing material produces elec-trochemical signals generating quantitative data. In addition, it triggers a difference in the reflectance of the sensing photonic film matrix. The analytical features of the biosensor were assessed in PBS buffer by electrochemical impedance spectroscopy (EIS) and by reflectance of the opal-based photonic crystal. The response of the proposed biosensor was in the range of physiological relevant levels of CEA (from 2.5 ng/mL to 10 ng/mL). This sensor was assembled on an ITO substrate as proof of concept, the best substrate among the several conductive material produced on glass support, even if the first part of the work focuses on the preparation of aluminum doped zinc oxide (AZO) thin films by RF sputtering and laser direct writing. These processes were optimized for the fabrication of a highly conductive and transparent oxide capable of replacing ITO in the future as a main component in most transparent and flexible electronics applications. The developed sensing device showed promising features to become a much simpler, faster and low-cost point-of-care (POC) portable solution for the detection of CEA when compared to conventional immunoassay approaches, due to its high sensitivity, stability and dual detection method. At the same time, it may open new doors for other applications and foreseen improvement concerning the early diagnosis of diseases

Organic Molecular Crystal Engineering via Organic Vapor-Liquid-Solid Deposition

Control over the size, shape, topology, orientation, and crystallographic phase of organic molecular materials is critical for a wide array of applications ranging from optoelectronics to pharmaceutical development. Herein, we demonstrate a relatively low-cost approach for fabricating single crystals with controlled sizes, shapes, microscale periodic features, preferred orientations and specific molecular packing modes. These features allow for the fabrication of intricate arrangements of single crystals for incorporation into complex device architectures, and potentially the endowment of tailored optical, electronic, thermal, and mechanical properties onto these materials. Patterning is achieved by utilizing an organic-vapor-liquid-solid (OVLS) deposition scheme paired with traditional photolithography methods. The OVLS approach involves spin coating a layer of a low vapor pressure solvent onto a substrate in order to drive up the critical nucleus size required for crystal nucleation, resulting in large grain sizes. This substrate is placed above a hot plate with the organic material to be sublimed. Our results show that millimeter-scale, ultrathin, planar organic molecular crystals can be grown on patterned substrates with rudimentary equipment (hot plate, spin coater, photoresist, photomask, UV source). We show that this technique is not only compatible with organic semiconductors, but also other organic molecular crystals such as pharmaceuticals

Large-Area Plasmonics on Self-Organized Wrinkled Nanopatterns

The focus of my PhD project consisted in the development of self-organized, large area, industrially scalable physical methods based on wrinkling instabilities to nanopattern and functionalize tunable plasmonic polymeric polydimetilsyloxane (PDMS) and solid-state glass surfaces, both transparent, non-toxic and cheap materials, for applications of significant technological interest in photonics and bio-sensing

Electro-spinning/netting: A strategy for the fabrication of three-dimensional polymer nano-fiber/nets.

Since 2006, a rapid development has been achieved in a subject area, so called electro-spinning/netting (ESN), which comprises the conventional electrospinning process and a unique electro-netting process. Electro-netting overcomes the bottleneck problem of electrospinning technique and provides a versatile method for generating spider-web-like nano-nets with ultrafine fiber diameter less than 20 nm. Nano-nets, supported by the conventional electrospun nanofibers in the nano-fiber/nets (NFN) membranes, exhibit numerious attractive characteristics such as extremely small diameter, high porosity, and Steiner tree network geometry, which make NFN membranes optimal candidates for many significant applications. The progress made during the last few years in the field of ESN is highlighted in this review, with particular emphasis on results obtained in the author's research units. After a brief description of the development of the electrospinning and ESN techniques, several fundamental properties of NFN nanomaterials are addressed. Subsequently, the used polymers and the state-of-the-art strategies for the controllable fabrication of NFN membranes are highlighted in terms of the ESN process. Additionally, we highlight some potential applications associated with the remarkable features of NFN nanostructure. Our discussion is concluded with some personal perspectives on the future development in which this wonderful technique could be pursued

Optical techniques for 3D surface reconstruction in computer-assisted laparoscopic surgery

One of the main challenges for computer-assisted surgery (CAS) is to determine the intra-opera- tive morphology and motion of soft-tissues. This information is prerequisite to the registration of multi-modal patient-specific data for enhancing the surgeon’s navigation capabilites by observ- ing beyond exposed tissue surfaces and for providing intelligent control of robotic-assisted in- struments. In minimally invasive surgery (MIS), optical techniques are an increasingly attractive approach for in vivo 3D reconstruction of the soft-tissue surface geometry. This paper reviews the state-of-the-art methods for optical intra-operative 3D reconstruction in laparoscopic surgery and discusses the technical challenges and future perspectives towards clinical translation. With the recent paradigm shift of surgical practice towards MIS and new developments in 3D opti- cal imaging, this is a timely discussion about technologies that could facilitate complex CAS procedures in dynamic and deformable anatomical regions