Optimizing Polymer Lab-on-Chip Platforms for Ultrasonic Manipulation: Influence of the Substrate

Abstract

Abstract:The choice of substrate material in a chip that combines ultrasound with microfluidics for handling biological and synthetic microparticles can have a profound effect on the performance of the device. This is due to the high surface-to-volume ratio that exists within such small structures and acquires particular relevance in polymer-based resonators with 3D standing waves. This paper presents three chips developed to perform particle flow-through separation by ultrasound based on a polymeric SU-8 layer containing channelization over three different substrates: Polymethyl methacrylate (PMMA); Pyrex; and a cracked PMMA composite-like structure. Through direct observations of polystyrene microbeads inside the channel, the three checked chips exhibit their potential as disposable continuous concentration devices with different spatial pressure patterns at frequencies of resonance close to 1 Mhz. Chips with Pyrex and cracked PMMA substrates show restrictions on the number of pressure nodes established in the channel associated with the inhibition of 3D modes in the solid structure. The glass-substrate chip presents some advantages associated with lower energy requirements to collect particles. According to the OPEN ACCESSMicromachines 2015, 6 575 results, the use of polymer-based chips with rigid substrates can be advantageous for applications that require short treatment times (clinical tests handling human samples) and low-cost fabrication.

A Label Free Disposable Device for Rapid Isolation of Rare Tumor Cells from Blood by Ultrasounds

“…According to their physical properties, several cultured pancreas cancer line cells TCs (Φ TC > 15 μm) were laterally entrained by the acoustic radiation force to reach the central node of pressure, keeping the smaller WBCs (Φ WBC ≤ 15 μm) flowing beside the channel walls at flow rate of 20 µL/min ≤ Q ≤ 100 µL/min and certain voltages supplied to the expectated piezoelectric ceramic. These results also agree with other studies in the literature reporting acoustic separation of TCs from WBCs [ 35 , 36 , 37 ].…”

“…On the contrary, recently developed 3D chip resonators allow the use of structural materials of a low acoustic impedance and stiffness, such as polymers. These structures do not impose strict restrictions in the channel width, as reported previously by our group [ 30 , 37 ]. These devices are suitable for bio-applications due to their high bio-compatibility and low-cost manufacture.…”

A 3D analysis of the acoustic radiation force in microfluidic channel with rectangular geometry

“…Many theoretical studies of 3D standing waves have reported numerical solutions of the governing equations obtained using the COMSOL Multiphysics ® finite element software [19][20][21]. It has also been shown that the acoustophoretic particle motion can be modeled using numerical solutions of the equations of motion with code that includes iterative methods such as a fourth-order Runge-Kutta [22][23][24]. Such software solutions decrease calculation time, facilitate study and accurate prediction of the simultaneous acoustophoretic motion of many particles or cells, and can be used to model dynamics of the aggregation processes in resonant chambers and to optimize separation throughput in different applications.…”

Microparticle Acoustophoresis in Aluminum-Based Acoustofluidic Devices with PDMS Covers

“…Simple mass-produced glass capillary tubes have been used for trapping of microparticles [2][3][4][5][6][7] and even nanoparticles [8,9]. The first attempts of using polymer-based devices have been published showing applications such as focusing of polymer beads [10][11][12][13], lipids [10], and red blood cells [11,14], as well as blood-bacteria separation [15] and purification of lymphocytes [16]. Although a cheaper material, polymers are difficult to use in acoustofluidics due to their low acoustic contrast relative to water, but recently it was shown how to circumvent this problem by use of the whole-system-resonance principle [17].…”