Harmonic Microchip Acoustophoresis: A Route to Online Raw Milk Sample Precondition in Protein and Lipid Content Quality Control

Abstract

A microfluidic approach for raw milk sample preconditioning prior to protein and lipid content analysis has been developed. The system utilizes microchip acoustophoresis and is a further extension of our previously reported multiple node ultrasonic standing wave focusing platform (Grenvall, C., Augustsson, P., Matsuoka, H. and Laurell, T. Proc. Micro Total Anal. Syst. 2008, 1, 161-163). The microfluidic approach offers a method for rapid raw milk quality control using Fourier transform infrared spectroscopy (FT-IR). Two acoustophoresis modes are explored, 2 lambda/2 and 3 lambda/2, offering lipid content enrichment or depletion, respectively. Lipid content depletion above 90% was accomplished. FT-IR data on microchip-processed raw milk samples, enabling direct lipid and protein content analysis, are reported. Most importantly, the harmonic operational modes bypass the problem of lipid aggregation and subsequent clogging, inherent in lambda/2 acoustophoresis systems.

Label‐free somatic cell cytometry in raw milk using acoustophoresis

“…[Color figure can be viewed in the online issue which is available at wileyonlinelibrary.com] linkage peak at 1,750 cm 21 (dashed circle) indicates a factor 6 in lipid depletion. This aligns with our previously reported experiments, which had longer acoustic exposure times, thus resulting in higher depletion rates (11). Most important, though, is that the removed lipid vesicles composed the larger size fraction as measured by Coulter counting and multiangle light scattering.…”

“…To enable efficient lipid removal from raw milk samples, an acoustically resonating microfluidic chip was fabricated in silicon with an anodically bonded glass lid (11,13). The acoustophoresis channel was 25-mm long, having a width of 1,125 lm and a depth of 150 lm, as shown in Figure 1.…”

“…The result of a representative measurement is shown in Figure 7, where the ester (b) However, at lower flow rates lipids start to aggregate/trap at the trifurcation branch as well as further down the channel (top-bottom aggregation). It should be noted that with a conventional single node channel lipid aggregation would occur even at higher flow rates, see (11). [Color figure can be viewed in the online issue which is available at wileyonlinelibrary.com] linkage peak at 1,750 cm 21 (dashed circle) indicates a factor 6 in lipid depletion.…”

“…Recently, it was demonstrated that lipid particles can be efficiently removed from raw milk samples using acoustophoresis to allow direct protein and lipid content analysis (11). In this report, we demonstrate how a combination of acoustophoresis and conventional Coulter Counting or phase contrast microscopy can be used to count the number of somatic cells in raw milk samples, using only an isotonic solution of NaCl as additional buffer.…”

Measuring the local pressure amplitude in microchannel acoustophoresis

“…[11][12][13][14][15][16] Likewise, the development of continuous-flow-based separation and manipulation of particles and cells has progressed rapidly with the advent of precision microfabricated flow-through resonators operating in the laminar flow regime. [17][18][19][20][21][22][23][24][25][26] Both the area of acoustic trapping and continuous separation/manipulation show great promise for applications within flow cytometry, and much of the current technological development targets cell biology.…”