Highly efficient passive Tesla valves for microfluidic applications

Abstract

A multistage optimization method is developed yielding Tesla valves that are efficient even at low flow rates, characteristic, e.g., for almost all microfluidic systems, where passive valves have intrinsic advantages over active ones. We report on optimized structures that show a diodicity of up to 1.8 already at flow rates of 20 μl s−1 corresponding to a Reynolds number of 36. Centerpiece of the design is a topological optimization based on the finite element method. It is set-up to yield easy-to-fabricate valve structures with a small footprint that can be directly used in microfluidic systems. Our numerical two-dimensional optimization takes into account the finite height of the channel approximately by means of a so-called shallow-channel approximation. Based on the three-dimensionally extruded optimized designs, various test structures were fabricated using standard, widely available microsystem manufacturing techniques. The manufacturing process is described in detail since it can be used for the production of similar cost-effective microfluidic systems. For the experimentally fabricated chips, the efficiency of the different valve designs, i.e., the diodicity defined as the ratio of the measured pressure drops in backward and forward flow directions, respectively, is measured and compared to theoretical predictions obtained from full 3D calculations of the Tesla valves. Good agreement is found. In addition to the direct measurement of the diodicities, the flow profiles in the fabricated test structures are determined using a two-dimensional microscopic particle image velocimetry (μPIV) method. Again, a reasonable good agreement of the measured flow profiles with simulated predictions is observed.

Tesla Valve Microfluidics: The Rise of Forgotten Technology

“…Overall, the unique properties and design flexibility of the TV make it a promising technology for a wide range of microfluidic and macroscopic fluidic applications. Passive components like the TV channel are gaining increased attention in microfluidics and nanofluidics as they offer several advantages [18,19]. These components are costeffective and can be easily integrated with sensors, making them more attractive for research and development.…”

“…The third design is the TV derivatives (TVD), inspired by the original TV microchannel and its basic principle with improvised shapes or stages [19,23,39,[60][61][62]. An example of the design and fabrication process of the TVD is depicted in Fig.…”

“…An example of the design and fabrication process of the TVD is depicted in Fig. 5 [19]. Bohm et al presented TVD with optimized structures that exhibit a diodicity of 1.8 even at low flow rates of 20 μl/s, which is equivalent to a Reynolds number of 36.…”

Design and optimization of multistaged Tesla valves using response surface methodology

“…Because TVs have a fixed geometric shape, they can compensate for the disadvantages of traditional valves that have movable parts and are prone to damage [8]. Therefore, TVs can be used as a substitute for movable valves.…”

Finger-Actuated Micropump of Constant Flow Rate without Backflow

“…However, in the case of reverse flow, it loses a lot of energy as it travels up and down each passage and has the most devastating effect at the intersection junction. Therefore, the driving pressure required to reverse the flow is much higher than that required to move the fluid forward [100][101][102]. In addition, intense mixing is produced by increased lateral deflections of the streams at the intersection junction.…”