Nature inspired surface/interface engineering towards advanced device applications

Nature inspired surface/interface with multi-faceted functions possess promises in the frontier engineering applications in flexible electronics, energy harvesting, autonomous systems, bio-mimicking tissues, micro-fluidics, etc. Understanding the relationship between nature’s architecture and underlying science could bring enabling solutions to overcome the engineering challenges. A nature inspired surface with smart resilient features provides intrinsic complexity and their multiplicity under different stimuli, i.e. chemical, physical, electronic, mechanical and (in some cases) biological properties. By mimicking/harvesting a variety of surface and interfacial features from nature, the final composition will display an integrative design to provide further explorations in deciphering the hidden physics towards advanced device applications in real world. Specifically, we bring a few engineering examples with chemical/physical approaches to construct artificial nano/micro-structured surface, yield various functional surface for different application scenarios. • A porous layer has been realised to provide controllable generation of microarchitecture to exhibit an anti-corrosion behaviour under UV exposure with multifaceted characteristics such as profound solar absorptivity, thermal emissivity. By further treating the surface with silane, a hybrid layer has been established with superhydrophobic and anti-icing features which shares innate interests in thermal transport/aero-space engineering. • The structural conformation/ elastic instabilities of the surface are exploited to devise an extreme switchable configuration to develop a morphing strategy for switchable lipophilic/oleophobic properties. The geometrical shift of soft structure is instructed to create a steady transition of surface topology rendering a unique switchable transition that are widely inspired in sub-sea/offshore engineering for oil and water separation. • We also develop a highly-replenishable thermal energy harvesting technology via a dynamical elasto-bouncing process of polymeric hydrogel to translate the thermal energy into useful elasto-kinetic energy, then further converted into electrical energy via a simple piezo-material based system, which paves way for a future portable and conformable energy harvesting tool in the regions of extreme geo-thermal residencies and industries. • Using a one drop filling technique along with interfacial pinning points between hydrophilic and hydrophobic, a unique microfluidic approach is presented to create heterogenous structures. By exploiting the communication between swelling mismatch of different functional groups, driven via in-plane and through thickness heterogeity, a highly complex 3D soft reconfiguration is achieved which is activated by stimulation inputs. • The theoretical understandings are exploited in the above applied engineering scenarios, such as elastic mechanics, morphing structure, surface/interface interactions and kinetics of of the polymer systems experienced on a hot surface, which offers further insights into the elastic recoiling evolution and tunability of the system for effective energy translation efficiency. We hope above approaches shed more lights on the nature inspired structure in device engineering, thus, advance the knowledge in the frontier science

Electrospun plant-derived natural biomaterials for Tissue engineering

Plant-derived natural products are being used in medicine, and they are easily available for the production and use in tissue engineering based biological applications. Utilization of plant materials to treat human diseases is a common practice followed over many decades. In fact plant and its derivatives have been actively included in health management over thousands of years. The advent of phytochemical and phytopharmacological sciences has opened an arena to elucidate the structural and biological composition of several medicinal plant products. Their pharmacological effects depend on the supply of highly active water soluble compounds; however, due to their large molecular size most compounds are unable to cross the lipid membranes of the cells and therefore result in poor absorption resulting in loss of bioavailability and efficacy. Electrospinning makes it possible to combine the advantages of utilizing these plant materials in the form of nanofibrous scaffolds for delivering the active constituent at a sufficient concentration during the entire treatment period to the host site. The aim of this review is to highlight the potential applications of electrospun nanofibrous scaffolds based systems and herbal medicines in tissue engineering

Advanced 3D morphing transducers by smart hydrogel patterning

This paper demonstrates a unique way of creating heterogeneous layered structures of soft functional materials for advanced transducer applications. Hydrogel droplets with different composites were patterned by a “two-parallel plate” configuration used in microfluidics applications. Resulted heterogeneous layered structures of hydrogel were created, generating reconfigurable 3D (3-dimensional) deformation responding to discrete levels of stimulation inputs

A tunable morphing polyelectrolyte system for smart ocular applications

For the first time, a focal-length tunable intra-ocular lens (IOL) device has been realized by a standard-shaped, homogeneous “one material” system. Different to existing technologies, this poly(N-isopropylacrylamide) gel (PNIPAM) based polyelectrolyte system doesn’t require any additional materials (e.g. metal electrodes, movable mechanical structures) to achieve a controllable lens shape transformation for the focal-length shifting actuation. The designed morphological deformation mechanism employs ionic-strength responsive mechanical buckling via controlled swelling of PNIPAM in phosphate buffered saline (PBS) with similar concentration to human eye liquid. This unique approach will unlock great potential in a wide range of smart ocular applications

Controlled Cooperative Wetting Enabled Heterogeneous Structured 3D Morphing Transducers

A unique microfluidics approach for functional hydrogel patterning with multilayered heterogeneous structures is presented. Prepolymer solution droplets with differentiated sodium acrylate concentrations are dispensed/printed in a wetting‐controlled “two‐parallel plate” (TPP, like a Hele‐Shaw Cell) system. The gelation within the system enables hydrogel bilayer structures with reconfigurable 3D deformations driven by in‐plane and through‐thickness heterogeneity under stimuli‐responsive mask‐less swelling/deswelling. The cooperation between swelling mismatch of functional groups results in a higher complexity of 3D reconfiguration in responding to discrete levels of stimulation inputs. This facile patterning technology with an in‐built ionic hierarchy can be scaled up/down with advanced transducing functionalities in various fields

Stimuli-responsive gel impregnated surface with switchable lipophilic/oleophobic properties

In this paper, we developed a novel morphing surface technique consisting of a 3D printed miniature groove structure and injected stimuli-responsive hydrogel pattern, which is capable of switching between lipophilicity and oleophobicity under certain stimuli. Under swelling, the geometrical change of the hydrogel will buckle the surface due to the structural confinement and create a continuous transition of surface topology. Thus, it will yield a change in the surface wetting property from oleophilic to super-oleophobic with a contact angle of oil of 85° to 165°. We quantitatively investigate this structure–property relationship using finite element analysis and analytical modeling, and the simulation results and the modeling are in good agreement with the experimental ones. This morphing surface also holds potential to be developed into an autonomous system for future sub-sea/off-shore engineering applications to separate oil and water

Controllable Synthesis of Upconversion Nanophosphors towards Scale-up Productions

Upconversion nanophosphors (UCNPs) have been considered as an important synthesis arm within biomedical and energy sectors due to their unique optical characteristics, which can convert near infrared (NIR) light into higher energy emissions. However, key challenges, e.g. cost, compatibility of the materials, etc. have to be taken into serious consideration to transform this in-lab UCNPs technology into scale-up production for wider commercial needs. This review highlights the fundamental concepts of synthetic approaches for upconversion nanophosphors and re-cap recent advances interms of large-scale production. A number of typical synthesis routes in both batch and continuous processes are reviewed, alongside their limitations and potential improvements when being considered for mass production. By discussing and exploiting the technical compacity for the potential synthetic trend, key challenges and expectations of future synthesis methods for UCNPs are also outlined

A Highly Controlled Fabrication of Porous Anodic Aluminium Oxide Surface with Versatile Features by Spatial Thermo-anodization

Thermo-anodization technology has been considered as an effective means to improve the thermal, physical and chemical properties for metal alloy. In this work, we achieve a porous black layer on the surface of aluminium alloy through an environmentally friendly anodic oxidation process, with a high thermal emittance (0.96) and a high solar absorptivity (0.921). In addition, the black thermo-anodized coating layer shows a unique anti-corrosion property under UV irradiation. A hybrid hydrophobic surface has been facilitated through treating the thermo-anodized porous layer with silane. Moreover, an anti-icing feature can be realised that can effectively delay the freezing of water droplet on the surface of AA2024 aluminium alloy. As such, the specific anodic process of coating provides a simple method for improving the solar absorptivity and infrared emittance of aluminium alloys, enabling broad applications in aerospace engineering

Research for a Better Tomorrow: Communicating with and engaging non expert audiences

This is a book of abstracts from Northumbria University's Faculty of Engineering and Environment's Postgraduate Research Conference, held on 21st June 2018

Liquid Marbles in Liquid

Traditional liquid marbles (LMs), liquid droplets encapsulated by hydrophobic particles at the liquid–gas interface, are restricted by their short lifetime and low heat transfer efficiency. Herein, a new paradigm for LMs immersed in various liquid mediums with massive enhanced heat transfer and spatial recognition is designed; without compromising the structural integrity, the lifetime of the liquid marbles in liquid (LMIL) is extended by ≈1000 times compared to classical LMs in air or naked droplets in organic reagents. The LMIL shows promising reverse structural re‐configurability while under external stimuli and maintaining their functionality for a very long period of time (≈weeks). These superior behaviors are further exploited as a miniature reactor with prolonged lifetimes and excellent temperature control, combined with its feasible operation, new opportunities will open up in the advanced chemical and biomedical engineering fields. It is also shown that LMIL can be applied in methylene blue degradation and 3D in‐vitro yeast cell cultures. These findings have important implications for real‐world use of LMs, with a number of applications in cell culture technology, lab‐in‐a‐drop, polymerization, encapsulation, formulation, and drug delivery