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Magnetically actuated bio-inspired metamaterials

Periodic Reporting for period 2 - ABIOMATER (Magnetically actuated bio-inspired metamaterials)

Reporting period: 2016-11-01 to 2019-04-30

One of the main technological problems currently addressed by a number of research groups is the development of microscopic machines/robots capable of operating at fluidic environments. This problem is related to a number of technological needs/applications which are essential in providing further breackthroughs in the areas of bio-medicine and bio-technology. The ABIOMATER project aims to deliver a new class of metamaterials whose mechanical and optical properties can be controlled by external magnetic fields. Central to this aim is the development of the basic building-block of the metamaterial, the micromotor, composed of interacting ferromagnetic particles with different anisotropic properties, connected by an elastic link. Individually, the micromotors provide solutions for generating propulsion in viscous (low Reynold’s number) fluids. Going beyond this, the ABIOMATER project aims to link micromotors together to form magneto-elastic membranes, a new type of metamaterial. Exploration of the functionality of these new materials will lead to the development of prototype devices, providing novel solutions to applications in microfluidics, optics and the biosciences.

The specific objectives of the ABIOMATER project are to:
1) Implement and demonstrate a microscopic version of the micromotor;
2) Develop and explore, both experimentally and theoretically, magneto-elastic membranes based on the microscopic motors;
3) Build and explore experimentally and theoretically prototype devices, including 3D microfluidic constructs, microfluidic pump, cell growth templates, tuneable optic/photonic materials and artificial muscle analogues.
As detailed above the three consecutive objectives relate to three stages of the development from a concept to a workable prototypes of devices that can be taken further for implementation in a number of technologies in a broad spectrum of applications. Consequently, the three main work packages addressed these stages of the development in which all partners were involved and provided the expertise or research capabilities needed for each of the stages.
The main challenge of the first Work Package and its tasks, which constitute the bulk of the first year of the project, was to implement a microscopic version of a single micromotor and explore its performance. As part of this WP we have successfully created fabrication procedures for construction of the devices. Based on the initially proposed methodology, the teams investigated different different methods, materials and techniques for making the devices. In the following tasks the teams have built the necessary formalism and numerical tools for understanding the properties of micromotors and exploring the relevant parameter space related to the geometric design and the surrounding external conditions of the micromotors. In particular, different regimes of the actuating magnetic fields and interaction between the micromotors and external surfaces, and between the micromotors within a larger linked agglomerate, were investigated. Then the swimming characteristics were investigated for liquid/air and liquid/surface interfaces and the ability to control the direction of propagation related to the regimes of motion.

In the second Work package, the main objectives were to explore different ways of implementations of 2D membranes and explore their fluidic and mechanical properties. Following the explored fabrication procedures for unit devices, based on PDMS and electroplated Co and CoNiP ferromagnets, 2D membranes were implemented. To improve on the magnetic forces a new designs based on magnetic torque were proposed, and successfully implemented. The new designs required an additional symmetry breaking mechanisms which were achieved by different elasticity and later by phase relation between the magnetic moments of different units (in the ‘paddle’ system design). The following tasks focused on experimental study of membranes, examining the mechanical and fluidic properties. We also examined alternatives approaches based on self-assembled microscopic membranes (based on magnetic beads). Theoretical studies of 2D structures considered a range of models spanning from the simulation on hard-soft type devices, a two-dimensional lattice of cilia and others.

Work package three extended the work to target a practical application of prototype materials. In tasks 1 and 2 UNEXE with support of UB has successfully demonstrated several prototype devices for microfluidic applications. This included the systems both on single unit devices (such as hard-soft particle and cilia type systems) and multiple 2D structures. The devices were tested in a practical size microfluidic environment, and demonstrated fluid flow at rates (~1mm/s, for 1x1mm) suitable for technological application. It was also demonstrated that in a system of multiple channels, the devices can be used for a directional control of flow, allowing an instant switching of the flows between different channels. The devices were also utilised as mixers and stirrers, demonstrating the capability of mixing at low Reynolds number. Task 3 concentrated on use of the membranes as bioreactors. Consequently, work focused on the development of a bioreactor which could trigger insulin release from pancreatic cells, and could possibly be used as part of a cure for diabetes. Strong increase in insulin secretion was observed for cells grown on MEMs with embedded FeNi particles after application of rotating magnetic field over a period of 10 min. In task 4 CEA in collaboration with UOXF focused on the use of 2D membranes as tuneable optical devices. The teams explored the mechanical properties of the membranes activated with magnetic fields in air. In task 5 the mechanical deformation of membranes was examined in the liquid media to explore its visco-elastic properties in real biological systems. It was found that the forces calculated for our membranes actuation can be in the order of magnitudes of natural forces measured in cells or other micro-organisms, acting with muscle-like behavior.
The main objective of the ABIOMATER project was to implement theoretically and experimentally a new range of materials based on a concept of a microscopic ferromagnetic swimmer. Furthermore, the project has set a target not only demonstrating the capability of creating the materials, but also employing them in varies devices for a range of technological applications. In particular, the project has focused on microfluidic applications which have an enormous need in modern medicine and biotechnology. The methodologies developed demonstrated that it was possible not only prove the experimental verification of the proposed concept but also build the devices that would be scalable for a mass production and using the tools and procedures currently available in industry. We believe this was successfully achieved and the project have demonstrated microfluidic prototype devices which could be taken further for implementation on an industrial scale. Furthermore, given the broad flexibility in the design and geometry of the system it can be easily modified and improved with no extra cost for fabrication processes. This offers a great potential for production of low-cost disposable microfluidic chips which would be invaluable in medical diagnostics and biotechnology.