Bidirectional microfluidic pumping using an array of magnetic Janus microspheres rotating around magnetic disks

Use of magnetic fluids in process system for pipe isolations

This paper investigates the use of magnetic fluids known as ferrofluids to act as ad hoc valves within pipe systems to create isolation points for stemming pipe leakages and to halt leakages before they become largescale disasters. The sealing abilities of ferrofluids were proven for microvalves (ID ≤ 1 mm) in hydrostatic experiments and extended to the macroscale applications (ID ≥ 6 mm). Theoretical prediction and magnetic finite element analysis (FEA) were also undertaken to predict the burst pressure, and a comparison of both results against the experimental measurement was made. The up-scale results (10-18 mm ID) indicated that it is feasible to develop a ferrofluid that can be extended to approximate the applicable magnet strength to achieve higher burst pressure. It was concluded that the ferrofluid isolation valves hold potential in macroscale environments for process engineering in favour of a positive isolation.

Optically Controlled Living Micromotors for the Manipulation and Disruption of Biological Targets

Bioinspired and biohybrid micromotors represent a revolution in microrobotic research and are playing an increasingly important role in biomedical applications. In particular, biological micromotors that are multifunctional and can perform complex tasks are in great demand. Here, we report living and multifunctional micromotors based on single cells (green microalgae: Chlamydomonas reinhardtii) that are controlled by optical force. The micromotor's locomotion can be carefully controlled in a variety of biological media including cell culture medium, saliva, human serum, plasma, blood, and bone marrow fluid. It exhibits the capabilities to perform multiple tasks, in particular, indirect manipulation of biological targets and disruption of biological aggregates including in vitro blood clots. These micromotors can also act as elements in reconfigurable motor arrays where they efficiently work collaboratively and synchronously. This work provides new possibilities for many in vitro biomedical applications including target manipulation, cargo delivery and release, and biological aggregate removal.

Controlling collective rotational patterns of magnetic rotors

Magnetic actuation is widely used in engineering specific forms of controlled motion in microfluidic applications. A challenge, however, is how to extract different desired responses from different components in the system using the same external magnetic drive. Using experiments, simulations, and theoretical arguments, we present emergent rotational patterns in an array of identical magnetic rotors under an uniform, oscillating magnetic field. By changing the relative strength of the external field strength versus the dipolar interactions between the rotors, different collective modes are selected by the rotors. When the dipole interaction is dominant the rotors swing upwards or downwards in alternating stripes, reflecting the spin-ice symmetry of the static configuration. For larger spacings, when the external field dominates over the dipolar interactions, the rotors undergo full rotations, with different quarters of the array turning in different directions. Our work sheds light on how collective behaviour can be engineered in magnetic systems.

A challenge of magnetically-actuated devices is to obtain different behaviours from each component under the same driving field. Here the authors tune the dipolar interactions between rotors to obtain different rotational behaviours when actuated by a magnetic field leading to complex collective dynamics.

Manual centrifuge system: Bearing-based hand spinner made with 3-D printer

Compact disk (CD) Microfluidic platforms are being studied for medical applications such as blood tests. However, its size is bulky and electricity is needed to realize centrifuge force. In this paper, bearing-based hand spinner is designed using three-dimensional printer. This spinner does not need electricity and keeps rotating direction unlike paperfuge while it is spinning. The properties of spinner vary depending on bearing type which is positioned at the center. The type of weighting area also affects change in RPM over time. When a separation experiment is implemented, separating mixture into red ink and oil and whole blood into red blood cell and plasma are achieved properly with ceramic ball bearing.