Active nematic pumps (2407.09960v2)

Abstract: Microfluidics involves the manipulation of flows at the microscale, typically requiring external power sources to generate pressure gradients. Alternatively, harnessing flows from active fluids, which are usually chaotic, has been proposed as a paradigm for the development of micro-machines. Here, by combining experimental realizations and simulations, we demonstrate that the addition of triangular-shaped inclusions into an active nematic gel can locally break the fore-aft symmetry of active turbulence and stabilize flow fields with self-pumping capabilities. The proposed strategy has enabled us to generate wall-free and self-powered microfluidic systems capable of both cargo transport and mixing along with the downstream flow. We analyze the performance of these active pumps, both isolated and within cooperative ensembles in terms of their output velocity and hydrostatic pressure buildup. Finally, we demonstrate strategies to incorporate them into specifically designed microfluidic platforms to advantageously tailor the geometry of active flows. Our results reveal new possibilities for leveraging the self-organized mechanodynamics of active fluids.

• The paper demonstrates a novel approach by embedding triangular inclusions in active nematic gels to induce unidirectional flows for self-powered microfluidic pumping.
• It employs combined experimental techniques and simulations to quantify optimal pumping efficiency at obstacle sizes matching the active length scale.
• The findings suggest scalable, wall-free microfluidic systems with potential applications in bio-inspired micromachines and adaptive fluid control.

Active Nematic Pumps: Engineering Microfluidic Systems Using Active Fluids

The paper "Active nematic pumps" presents a comprehensive paper on utilizing active nematic (AN) gels to engineer self-powered microfluidic systems. Notably, the authors explore the integration of triangular-shaped inclusions into an AN gel to harness the chaotic motion of active fluids, thus pioneering the development of novel micro-machinery for fluid manipulation. This work combines experimental approaches and simulations to reveal the profound capabilities of active nematics in stabilizing flow fields to achieve self-pumping capabilities.

In the field of microfluidics, traditional systems heavily rely on external power sources to maintain pressure gradients. This paper explores an innovative alternative, employing the inherent flows from active fluids to bypass the constraints of conventional microfluidic paradigms. A promising aspect lies in the breakage of fore-aft symmetry within the turbulence of active nematics by strategically embedding triangular inclusions. This configuration catalyzes structured, unidirectional flows, facilitating autonomous transport and mixing without the confines of solid walls.

The authors introduce a layered strategy, systematically examining the operational dynamics of individual active pumps and exploring their behavior within cooperative arrays. They meticulously analyze pertinent performance metrics, such as output velocity and pressure buildup, unveiling a novel methodology for realizing wall-free active microfluidic systems. Central to these systems is the phenomena of active pumping, achieved through a collective effect stemming from vortex lattice formations induced by asymmetrical obstacles. The paper further investigates the scalability of these pumps, demonstrating that aligning multiple pumps in series or parallel augments the overall system efficiency akin to hydraulic counterparts.

From a results perspective, both experimental and simulation datasets corroborate the feasibility of active nematic pumps. Strong numerical results illustrate how the active flow fields organize into net unidirectional transport, reinforcing the potential for these systems in practical microfluidic applications. Additionally, the research exemplifies how triangular obstacles with lengths comparable to the active length scale ($D_{def}$) can optimize flow rectification and pressure gradients. Specifically, results show a peak pumping efficiency with obstacle sizes aligned to the intrinsic active length scale, subsequently declining for larger configurations.

The implications of these findings hold promise across various interdisciplinary fields. The mechanodynamic capabilities demonstrated could redefine bio-inspired micromachines, ushering in a new era of microfluidic technologies that leverage active matter. These systems harbor the potential to serve as autonomous platforms for microcargo transport, chemical mixing, and even adaptive flow geometries in response to environmental contingencies.

Looking ahead, further research could expound upon the versatility of active nematic pumps, extending the concept to diverse geometries and application domains. Investigations could also probe into minimizing energy dissipation or enhancing the scalability and robustness of such systems. Additionally, a broader exploration into the integration with biological entities or other self-driven systems could present profound advancements in bioengineering and synthetic biology.

In conclusion, the paper provides significant insights into the functionalities of active nematic fluids, demonstrating how structured inclusions can yield robust, self-driven systems for microfluidic applications. By bridging the gap between the inherently turbulent nature of active fluids and the structured flow requirements of microfluidics, this paper paves the way for future inventions in the field. As the technology matures, it promises not only to enhance current capabilities but also to open avenues for innovative solutions previously constrained by traditional microfluidic approaches.