Facile and cost-efficient development of PMMA-based nanocomposites with custom-made hydrothermally-synthesized ZnO nanofillers

Over the past few years polymer nanocomposites have attracted considerable interest within the scientific community because they not only combine several alluring properties such as low weight, cost-efficiency and ease-of-formability, but mainly because they possess multi-faceted, multi-functional capabilities suitable for a wide range of applications, especially in the area of printed electronics. In this work, a two-step study was performed with the aim of developing ZnO/poly(methyl methacrylate) (PMMA) nanocomposites. The first step of the study encompassed the development of a facile, low-cost hydrothermal methodology to synthesize customized ZnO-nanostructures of controllable morphology and the detailed examination of the role of the materials used on the final shape and size of the produced nanostructures. The second step included studies to optimize the embedding of the produced nanostructures into PMMA matrices, mostly concentrating on the role of the solvent. The produced ZnO/PMMA nanocomposites were coated onto Si-based interdigitated electrode devices to explore their electrical characteristics and assess their potential to be employed for sensing applications. © 2018 Elsevier B.V

Cuo/pmma polymer nanocomposites as novel resist materials for e‐beam lithography

Polymer nanocomposites have emerged as a new powerful class of materials because of their versatility, adaptability and wide applicability to a variety of fields. In this work, a facile and cost‐effective method to develop poly(methyl methacrylate) (PMMA)‐based polymer nanocompo-sites with copper oxide (CuO) nanofillers is presented. The study concentrates on finding an appro-priate methodology to realize CuO/PMMA nanocomposites that could be used as resist materials for e‐beam lithography (EBL) with the intention of being integrated into nanodevices. The CuO nanofillers were synthesized via a low‐cost chemical synthesis, while several loadings, spin coating conditions and two solvents (acetone and methyl ethyl ketone) were explored and assessed with regards to their effect on producing CuO/PMMA nanocomposites. The nanocomposite films were patterned with EBL and contrast curve data and resolution analysis were used to evaluate their performance and suitability as a resist material. Micro‐X‐ray fluorescence spectroscopy (μ‐XRF) complemented with XRF measurements via a handheld instrument (hh‐XRF) was additionally em-ployed as an alternative rapid and non‐destructive technique in order to investigate the uniform dispersion of the nanofillers within the polymer matrix and to assist in the selection of the optimum preparation conditions. This study revealed that it is possible to produce low‐cost CuO/PMMA nanocomposites as a novel resist material without resorting to complicated preparation techniques. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Mechanism of Polycomb recruitment to CpG islands revealed by inherited disease-associated mutation.

How the transcription repressing complex Polycomb interacts with transcriptional regulators at housekeeping genes in somatic cells is not well understood. By exploiting a CpG island (CGI) point mutation causing a Mendelian disease, we show that DNA binding of activating transcription factor (TF) determines histone acetylation and nucleosomal depletion commensurate with Polycomb exclusion from the target promoter. Lack of TF binding leads to reversible transcriptional repression imposed by nucleosomal compaction and consolidated by Polycomb recruitment and establishment of bivalent chromatin status. Thus, within a functional hierarchy of transcriptional regulators, TF binding is the main determinant of Polycomb recruitment to the CGI of a housekeeping gene in somatic cells

Selective immobilization of proteins guided by photo-patterned poly(vinyl alcohol) structures

AbstractThe development of “protein resistant” materials is challenging since protein hysisorption takes place on most surfaces due to van der Waals interactions, hydrogen bonding and entropy effects. In this work a new process for converting a surface resistant to protein adsorption is presented by using a photo-patternable poly(vinyl alcohol) (PVA) based film. This material minimizes effectively protein physisorption and it can be patterned through photolithography on top of any substrate. Herein the PVA-based film is patterned on top of a poly(styrene) (PS) film, in order to achieve selective protein patterning on the PS film and demonstrate the resistance of the PVA-based material to protein physisorption. The proposed methodology is expected to facilitate the fabrication of sensors and bioelectronic devices since it provides a patterning route with alignment capabilities for protein resistant-surfaces and it is based on an easy to implement process

Biomolecular layer thickness evaluation using White Light Reflectance Spectroscopy

A White Light Reflectance Spectroscopy (WLRS) methodology is applied in the evaluation of the effectiveness of biomolecules immobilization onto solid surfaces as well as their subsequent reaction with counterpart biomolecules via measuring the respective layers thickness. In particular we investigated the adsorption of rabbit and mouse gamma-globulins as well as their reaction with complementary antibodies. The results obtained with the proposed methodology were compared with those received by atomic force microscopy analysis of the same samples. It was found that the developed method provides a simple, very fast and accurate approach for thin biomolecular layers thickness determination

Growth and characterization of uniform ZnO films as piezoelectric materials using a hydrothermal growth technique

ZnO nanostructures, especially in the form of dense arrays of nanorods or belts have the ability to efficiently convert mechanical energy to electrical energy. One of the drawbacks though for the exploitation of nanorod technology for commercial devices is the ability to make the electrical contacts to these nanostructured piezoelectric converting elements. Although technologies have been developed that provide solutions for electrical contact issues, metal contact on uniform thin films are much simpler, and can readily be implemented to commercial mass-produced applications. At the same time it is known that high piezoelectric coefficients ZnO uniform films with columnar grains having their c-axis perpendicular to the substrate are required. In this work, we investigate the growth of uniform ZnO films, using a low temperature, low cost hydrothermal process typically used for the fabrication of ZnO nanorods. Under appropriate conditions coalescence of the nanorods occur resulting in uniform films with a columnar structure. The study focuses on understanding the role of the growth factors in order to be able to fully control the proposed process. Moreover, the hydrothermal method is further exploited for the fabrication of uniform ZnO nanostructures on patterned substrates with Au interdigitated electrodes (IDE) using standard lithography as a proof-of-concept of the applicability of the method to standard microfabrication techniques. The piezoelectric films with the IDEs are electrically characterized in order to assess the electrical properties of the grown films. From this analysis, process conditions have been identified for the growth of uniform nanostructured ZnO films, suitable for piezoelectric microgenerators