A new class of magnetically actuated pumps and valves for microfluidic applications

Abstract

We propose a new class of magnetically actuated pumps and valves that could be incorporated into microfluidic chips with no further external connections. The idea is to repurpose ferromagnetic low Reynolds number swimmers as devices capable of generating fluid flow, by restricting the swimmers’ translational degrees of freedom. We experimentally investigate the flow structure generated by a pinned swimmer in different scenarios, such as unrestricted flow around it as well as flow generated in straight, cross-shaped, Y-shaped and circular channels. This demonstrates the feasibility of incorporating the device into a channel and its capability of acting as a pump, valve and flow splitter. Different regimes could be selected by tuning the frequency and amplitude of the external magnetic field driving the swimmer, or by changing the channel orientation with respect to the field. This versatility endows the device with varied functionality which, together with the robust remote control and reproducibility, makes it a promising candidate for several applications.

Microfluidic devices powered by integrated elasto-magnetic pumps

“…57 The Purcell 3-link swimmer is capable of producing tuneable flow rates when altering the phase difference of the two hinges, 49,50,58,59 and has been theorised to be capable of producing flow in the reverse direction, 60 however achieving reverse flow rates in this manner is experimentally impractical as it would require high amplitude deformation which has not yet been achieved experimentally. Hamilton et al 20 has shown that placing restrictions on the near-field fluid vortices around an elastomagnetic pump can constrain the resultant fluid flows into producing strong flow in the negative direction without altering the motion of the pump. In this manner, the flow direction can be controlled through much smaller changes in pump behaviour.…”

“…12 Generating net motion in the Stokes regime has been a lively area of study over the last few decades, underpinned by the work of Purcell 13 and Taylor, 14 and has grown into a diverse field with a multitude of swimming and pumping mechanisms being developed both theoretically and experimentally. Research in this field has explored a vast array of driving mechanisms, including magnetic torque, [15][16][17][18][19][20][21][22][23] electric fields, 24,25 light, 26,27 acoustic waves [28][29][30] and chemical energy. [31][32][33] Many of these driving mechanisms have been studied in the context of microscopic pumping solutions.…”

“…[31][32][33] Many of these driving mechanisms have been studied in the context of microscopic pumping solutions. 19,20,24,[34][35][36][37][38][39][40][41][42][43][44][45][46] While there is no formal way of comparing these systems directly, it is clear that many of these integrated pumping designs do not offer optimal solutions for use in a broad range of low-cost, portable POCT devices. For example, a device utilising capillary flow 45 can be fabricated and operated easily, although cannot produce tuneable or reversible fluid flow and is not appropriate for prolonged or repeated use.…”

Electro-actuated valves and self-vented channels enable programmable flow control and monitoring in capillary-driven microfluidics

“…However, such a manipulation has been typically addressed by developing complex microfluidic devices with moving structures and using bulky, specialized, and expensive peripherals, which also often require technically skilled users. A myriad of other integrated liquid control strategies, including manual (8), electrical (9), chemical (10), optical (11), magnetic (12), and thermal (13) actuation, have been developed, but they generally lack programmability and real-time feedback and still suffer from fabrication complexities and known issues associated with high-throughput manufacturing and integration of polydimethylsiloxane (PDMS) and hydrogels.…”

Advanced Processing of Micropatterned Elasto-Magnetic Membranes

“…Once activated with an oscillating magnetic field, the ferromagnetic swimmer is able to swim in liquid or pump fluids at a low Reynolds number regime. The devices have been successfully demonstrated experimentally [14], [15], however, the designs were implemented at a millimeter scale with the magnetic elements constructed using bulk materials (e.g. NdFeB magnets).…”