A minimized valveless electromagnetic micropump for microfluidic actuation on organ chips

Microfluidic chips have exhibited great potential for physiological and pathological studies. In particular, organ chips based on microfluidic device technology are promising replacement for traditional drug development methods due to its ability to physically and chemically mimic the internal environment of tissues and cells. For a better and realistic simulation of in vitro models, it is important to develop organ chips exhibiting dynamic culture through micropump actuation. Unfortunately, presently available micropump actuation methods are limited to specific applications as they do not meet the miniaturization and portability needs.

In a recent paper published in Sensors and Actuators A: Physical journal, Associate Professor Shengli Mi, Haitao Pu (MSc student), Shengyue Xie (MSc student), and Professor Wei Sun from Tsinghua University in China and Drexel University in USA developed a valveless electromagnetic micropump actuated organ chips. The chip comprised of three layers: coil layer, membrane layer, and channel layer while the power supply of the system comprised of a dry battery and a small signal generation module. The actuating performance of the electromagnetic micropump was investigated by measuring the flow rate.

A simplified electromagnetic micropump structure was presented. Instead of valves, the micropump utilized a nozzle diffuser. Consequently, the coil and magnet volume were significantly reduced to achieve a minimized size for easy integration on a microfluidic chip. Thus, the chip and micropump could be packaged for portability. Additionally, it exhibited a reduced dependence on the external power supply as the small-signal module and dry battery-package could adequately supply the coil. Furthermore, the minimized size and simplified structure allowed the integration of multiple electromagnetic micropumps on a single chip. For instance, micropumps could achieve complicated flow conditions for both series and parallel connections for accurate and realistic simulation of physiological fluid flow in different organ chips.

The microfluidic flow rate was measured under different square wave parameters including frequency, duty cycle and peak voltages to evaluate the actuating performance of the micropump. For actuation frequency less than 110Hz, the membrane deflection frequency increased with an increase in the actuation frequency resulting in a high flow rate. For actuation frequency greater than 110 Hz, however, the membrane achieved less deflection resulting in a slower flow rate. On the other hand, the magnetic field generated by the coil increased at peak voltage. This led to an increase in the magnetic force, membrane deflection, and consequently the flow rate.

As concept proof, the authors established the dynamic coculture of breast and liver cancer models on the chip by actuation of electromagnetic micropump and analyzed cell viability, albumin, and IL-6 at 24, 48, and 72 hours. Results showed that as an actuator, electromagnetic micropump resulted in dynamic coculture that exhibited significant contribution to the growth and function of the cell. Additionally, protein secretion in coculture was much greater than that for static coculture under the same experimental conditions even though the cell viability and amount of secreted proteins decreased with time. The study by Tsinghua University scientists will particularly improve the fabrication processes to develop high-performance micropumps.