Piezoelectrically driven vertical cavity acoustic transducers for the convective transport and rapid detection of DNA and protein binding to DNA microarrays with SPR imaging—A parametric study

Microfluidic Acoustic Method for High Yield Extraction of Cell-Free DNA in Low-Volume Plasma Samples

Cell-free DNA has many applications in clinical medicine, in particular in cancer diagnosis and cancer treatment monitoring. Microfluidic-based solutions could provide solutions for rapid, cheaper, decentralized detection of cell-free tumoral DNA from a simple blood draw, or liquid biopsies, replacing invasive procedures or expensive scans. In this method, we present a simple microfluidic system for the extraction of cell-free DNA from low volume of plasma samples (≤500 μL). The technique is suitable for either static or continuous flow systems and can be used as a stand-alone module or integrated within a lab-on-chip system. The system relies on a simple yet highly versatile bubble-based micromixer module whose custom components can be fabricated with a combination of low-cost rapid prototyping techniques or ordered via widely available 3D-printing services. This system is capable of performing cell-free DNA extractions from small volumes of blood plasma with up to a tenfold increase in capture efficiency when compared to control methods.

Ultrasound-Responsive Systems as Components for Smart Materials

Smart materials can respond to stimuli and adapt their responses based on external cues from their environments. Such behavior requires a way to transport energy efficiently and then convert it for use in applications such as actuation, sensing, or signaling. Ultrasound can carry energy safely and with low losses through complex and opaque media. It can be localized to small regions of space and couple to systems over a wide range of time scales. However, the same characteristics that allow ultrasound to propagate efficiently through materials make it difficult to convert acoustic energy into other useful forms. Recent work across diverse fields has begun to address this challenge, demonstrating ultrasonic effects that provide control over physical and chemical systems with surprisingly high specificity. Here, we review recent progress in ultrasound–matter interactions, focusing on effects that can be incorporated as components in smart materials. These techniques build on fundamental phenomena such as cavitation, microstreaming, scattering, and acoustic radiation forces to enable capabilities such as actuation, sensing, payload delivery, and the initiation of chemical or biological processes. The diversity of emerging techniques holds great promise for a wide range of smart capabilities supported by ultrasound and poses interesting questions for further investigations.

Versatile hybrid acoustic micromixer with demonstration of circulating cell-free DNA extraction from sub-ml plasma samples

Acoustic micromixers have attracted considerable attention in the last years since they can deliver high mixing efficiencies without the need for movable components. However, their adoption in the academic and industrial microfluidics community has been limited, possibly due to the reduced flexibility and accessibility of previous designs since most of them are application-specific and fabricated with techniques that are expensive, not widely available and difficult to integrate with other manufacturing technologies. In this work, we describe a simple, yet highly versatile, bubble-based micromixer module fabricated with a combination of low-cost rapid prototyping techniques. The hybrid approach enables the integration of the module into practically any substrate and the individual control of multiple micromixers embedded within the same monolithic chip. The module can operate under static and continuous flow conditions showing enhanced mixing capabilities compared to similar devices. We show that the system is capable of performing cell-free DNA extractions from small volumes of blood plasma (≤500 μl) with up to a ten-fold increase in capture efficiency when compared to control methods.

Rapid immunodiagnostics of multiple viral infections in an acoustic microstreaming device with serum and saliva samples

There is a growing need to screen multiple infections simultaneously rather than diagnosis of one pathogen at a time in order to improve the quality of healthcare while saving initial screening time and reduce costs. This is the first demonstration of a five-step protein array assay for the multiplexed detection of HIV, HPV and HSV antibodies on an integrated microfluidic system. HIV, HPV and HSV reactive antibodies from both serum and saliva were rapidly detected by acoustic streaming-based mixing and pumping to enable an integrated, rapid and simple-to-use multiplexed assay device. We validated this device with 37 serum and saliva samples to verify reactivity of patient antibodies with HIV, HPV and HSV antigens. Our technology can be adapted with different protein microarrays to detect a variety of other infections, thus demonstrating a powerful platform to detect multiple putative protein biomarkers for rapid detection of infectious diseases. This integrated microfluidic protein array platform is the basis of a potent strategy to delay progression of primary infection, reduce the risk of co-infections and prevent onward transmission of infections by point-of-care detection of multiple pathogens in both serum and oral fluids.

Ultra-sensitive detection by metal nanoparticles-mediated enhanced SPR biosensors

Surface plasmon resonance (SPR), as an optical technique, has widely been used for the detection of biomarkers. Various investigations have been conducted to address the impacts of SPR on the kinetics of biological interactions between the ligand and its cognate bio-element. Up until now, different biofunctionalized metal nanoparticles (NPs) have been used for the ultrasensitive detection of biomarkers in the enhanced SPR. The enhancement of plasmonic properties and refractive index by means of metal NPs in SPR-based biosensors have significantly improved the diagnosis and monitoring of molecular markers in different disesaes including malignancies. In all the enhanced SPR systems utilized for the direct/sandwich assay, each NP is covalently modified with the analyte molecules like antibody (Ab) or a nucleic acid such as DNA/RNA aptamer (Ap) capable of interaction with the related biomarker(s). The increasing of density near the gold surface and plasmonic coupling of gold film and NPs can provide a large shift in the refractive index enhancing the plasmonic resonance because the SPR response unit is sensitive to alteration of the refractive index and the mass shifting onto the chip surface. In this study, we review the potential applications of two major NPs for enhancing the SPR signals for the detection of molecular biomarkers, including gold and magnetic NPs.

Blood glucose monitoring with smartphone as glucometer

In this short communication, we redefine smartphone and enable it to monitor blood glucose as glucometer. The proposed smartphone is not only a mobile phone but also a medical device-glucometer. An electrometer module, acquiring the electrochemical current from the disposable enzymatic test strip on which a 0.5 μL human peripheral whole blood drop is placed, was integrated in the smartphone. The medical smartphone is capable of directly measuring blood glucose concentration and uploading into personal health center by the 4G mobile communication internet.

Nanotechnology-Based Surface Plasmon Resonance Affinity Biosensors for In Vitro Diagnostics

In the last decades, in vitro diagnostic devices (IVDDs) became a very important tool in medicine for an early and correct diagnosis, a proper screening of targeted population, and also assessing the efficiency of a specific therapy. In this review, the most recent developments regarding different configurations of surface plasmon resonance affinity biosensors modified by using several nanostructured materials for in vitro diagnostics are critically discussed. Both assembly and performances of the IVDDs tested in biological samples are reported and compared.

The breakup of digital microfluids on a piezoelectric substrate using surface acoustic waves

A new method for the breakup of a digital microfluid (a discrete droplet) is presented and a device for splitting the digital microfluid is fabricated on a 128° yx-LiNbO3 piezoelectric substrate using microelectronic technology. Together with the surface tension of the digital microfluid, the inertia of acoustic streaming caused by the sudden disappearance of the electric signal for generating the surface acoustic wave breaks up the digital microfluid. The escape angle of the daughter digital microfluids is calculated. A sound-absorption film is coated on the acoustic path to prevent the further breakup of the daughter digital microfluids. Droplet breakups are demonstrated using red dye solution digital microfluids. Results show that digital microfluids can be broken up by suddenly decreasing the power of the electrical signal from 12.3 dBm to -3.98 dBm, and the average escape angle of daughter digital microfluids is 68.5° for 4 μL of initial digital microfluid. The results also show that the escape angle is affected by the initial volume of the digital microfluid.

Cavity-induced microstreaming for simultaneous on-chip pumping and size-based separation of cells and particles

We present a microfluidic platform for simultaneous on-chip pumping and size-based separation of cells and particles without external fluidic control systems required for most existing platforms. The device utilizes an array of acoustically actuated air/liquid interfaces generated using dead-end side channels termed Lateral Cavity Acoustic Transducers (LCATs). The oscillating interfaces generate local streaming flow while the angle of the LCATs relative to the main channel generates a global bulk flow from the inlet to the outlet. The interaction of these two competing velocity fields (i.e. global bulk velocity vs. local streaming velocity) is responsible for the observed separation. It is shown that the separation of 5 μm and 10 μm polystyrene beads is dependent on the ratio of these two competing velocity fields. The experimental and simulation results suggest that particle trajectories based only on Stokes drag force cannot fully explain the separation behavior and that the impact of additional forces due to the oscillating flow field must be considered to determine the trajectory of the beads and ultimately the separation behavior of the device. To demonstrate an application of this separation platform with cellular components, smaller red blood cells (7.5 ± 0.8 μm) are separated from larger K562 cells (16.3 ± 2.0 μm) with viabilities comparable to those of controls based on a trypan blue exclusion assay.

Oscillating bubbles: a versatile tool for lab on a chip applications

With the fast development of acoustic and multiphase microfluidics in recent years, oscillating bubbles have drawn more-and-more attention due to their great potential in various Lab on a Chip (LOC) applications. Many innovative bubble-based devices have been explored in the past decade. In this article, we first briefly summarize current understanding of the physics of oscillating bubbles, and then critically summarize recent advancements, including some of our original work, on the applications of oscillating bubbles in microfluidic devices. We intend to highlight the advantages of using oscillating bubbles along with the challenges that accompany them. We believe that these emerging studies on microfluidic oscillating bubbles will be revolutionary to the development of next-generation LOC technologies.