Micro magnetic stir-bar mixer integrated with parylene microfluidic channels

Abstract

Previously, we reported a micro magnetic stir-bar mixer driven by an external rotating magnetic field and its rapid mixing performance in polydimethyl-siloxane (PDMS) channels. The PDMS piece with embedded fluid channels were manually aligned to a glass substrate and assembled. In this paper, we report the fabrication and testing results of a micro magnetic stir-bar monolithically integrated in parylene surface-micromachined channels with improved design features, including small tolerance of the stir-bar to channel wall (10 microm). Using of parylene based microchannels with improved design not only provides improved mixing, but also eliminates certain problems associated with PDMS-based channels. For example, porosity of PDMS causes evaporation and absorption of chemicals and thus channels made of PDMS are prone to cross-contamination. We have also demonstrated that the magnetic stir-bar can be used to pump liquid in micro channels.

An effective splitting-and-recombination micromixer with self-rotated contact surface for wide Reynolds number range applications

“…Passive micromixers 1, [8][9][10][11][12] do not require external energy but only depend on the structure of the channel, and the mixing mechanism relies entirely on molecular diffusion or chaotic advection. For achieving a high mixing efficiency, active micromixers usually utilize the disturbance induced by an external field, such as the electric field, [13][14][15][16] the acoustic field, [17][18][19][20] and the magnetic field, 21,22 etc. However, it is often difficult to fabricate active micromixers for their integration with complicated components that trigger external fields.…”

Polydimethylsiloxane-based conducting composites and their applications in microfluidic chip fabrication

“…Gong and W. Wen Biomicrofluidics 3, 012007 ͑2009͒ et al 48 developed an acoustically driven mixer based on the acoustic microstreaming principle; Shilton et al 49 demonstrated increased efficiency in particle concentration/separation and in generating intense micromixing in microliter drops by using concentric circular and elliptical transducers to focus the wave͒, and magnetohydrodynamics ͑Ryu et al 50 fabricated a magnetic stir bar composed of a free rotating rotor to which was applied a rotating external magnetic field͒. A cross-stream active mixer represents a system in which the flow in the main microfluidic channel is perturbed by actively controlled side-channel flows.…”

Fabrication of Nanopillar Micropatterns by Hybrid Mask Lithography for Surface-Directed Liquid Flow

“…In particular, microrobots on a chip have great advantages for the treatment of biological cells with high throughput, due to their high speed and high accuracy [3]. Several actuation methods of microrobots OPEN ACCESS have been proposed for microscale cell manipulation, such as optical tweezers [4,5], magnetic actuators [6,7] and bubble robots driven by optically induced thermocapillary flow [8]. In previous studies, we proposed magnetically driven micro-tools (MMTs) for on-chip cell manipulation [9][10][11][12].…”