Dissolvable membranes as sensing elements for microfluidics based biological/chemical sensors

Abstract

We demonstrate a chemical and biological sensing mechanism in microfluidics that transduces chemical and biological signals to electrical signals with large intrinsic amplification without need for complex electronics. The sensing mechanism involves a dissolvable membrane separating a liquid sample chamber from an interdigitated electrode. Dissolution of the membrane (here, a disulfide cross-linked poly(acrylamide) hydrogel) in the presence of a specific target (here, a reducing agent-dithiothreitol) allows the target solution to flow into contact with the electrode. The liquid movement displaces the air dielectric with a liquid, leading to a change (open circuit to approximately 1 kOmega) in the resistance between the electrodes. Thus, a biochemical event is transduced into an electrical signal via fluid movement. The concentration of the target is estimated by monitoring the difference in dissolution times of two juxtaposed sensing membranes having different dissolution characteristics. No dc power is consumed by the sensor until detection of the target. A range of targets could be sensed by defining membranes specific to the target. This sensing mechanism might find applications in sensing targets such as toxins, which exhibit enzymatic activity.

Dissolvable Polyvinyl-Alcohol Film, a Time-Barrier to Modulate Sample Flow in a 3D-Printed Holder for Capillary Flow Paper Diagnostics

“…With the use of PVA as a time barrier film, the sample will not flow until the required time. This allows increased exposure time between protein and antibody in order to allow more immuno-complexes to be formed in order to ensure higher sensitivity, reactivity, and reduced false-positive signal [1,2,5]. In addition, as previously discussed, the PVA solubility depends on its molecular weight and degree of hydrolysis.…”

“…In the presence of the sample, the membrane dissolves and permits the sample flow into interdigitated electrodes. This results in a resistance change between the electrodes and transduces the chemical event into an electrical signal [5]. However, in order for such dissolvable membranes to be employed in high-speed sensing technologies, the total operation time of the device should be approximately 30 min or less.…”

Acoustofluidic waveguides for localized control of acoustic wavefront in microfluidics

“…In addition, acoustofluidic waveguides with cross-sectional shapes other than circle, square, and triangle could also be exploited for the localized shaping of the acoustic fields in microfluidics. Our studies revealed that some of these structures are capable of yielding quite unique field profiles, which are extremely sensitive to the geometric modifications and/or the frequency changes, making themselves appealing platforms for some specific biomedical applications (Lee et al 2014; Liu et al 2012; Sridharamurthy et al 2006). Furthermore, through designing more complex structures (e.g., waveguide arrays) and introducing novel configurations like acoustic metasurfaces (Li et al 2013, 2014b; Xie et al 2014) and/or phononic crystals (Bourquin et al 2011; Lin et al 2009), we envision the exploitation of our acoustofluidic waveguide platform in realizing even more complex and integrated functionalities.…”

Interfacial formation of porous membranes with poly(ethylene glycol) in a microfluidic environment

“…The porous membrane, interfacially formed in situ , will enable relatively easy fabrication of microfluidic filtration devices. The porous membrane may also be applicable to biological applications, such as cell migration and invasion devices19 and detection devices 30, 31. However, further study should be done to investigate the biocompatibility of the porous membrane.…”