Ryan Sochol

ABSTRACT In this paper, we present a versatile ‘human-powered’ microfluidic system that encapsulates microbeads within droplets to perform a medical diagnostics assay. Point-of-care (POC) microfluidic devices hold great promise for medicinal applications throughout the world. In particular, portable, low-cost systems that can be operated by non-medical personnel without electrical supplies are desired. Here we present a PDMS microfluidic device (2.8 cm × 1.9 cm × 0.8 cm) to achieve four distinct accomplishments: (i) pressing force from a single human finger simultaneously actuates the flow for three distinct solutions/suspensions in parallel, (ii) functionalized “detection” microbeads (⊘ = 15 μ m) and biological reagents are simultaneously encapsulated together within microdroplets (⊘ ∼ 50 μm), and (iii) novel trapping architectures are utilized to ultimately immobilize the microbead-containing microdroplets for fluorescence detection. The presented system was employed to detect the inflammatory cytokine, interferon-gamma (IFN-γ), via aptamer beacons conjugated to microbeads — which represents the first time IFN-γ detection has been achieved using microbeads inside microdroplets.

Here we present and demonstrate the concept of a versatile 'human-powered' fluid pumps as a modular element to provide pressure head for a variety of microfluidic systems. Several distinctive accomplishments have been achieved: (1) human finger as the pumping actuation force; (2) pumping without using any electricity, (3) integrated pump with a passive safety valve and two one-way valves, and (4) successful demonstration in delivering fluids/particles into a microfluidic chip. For the first time, we have demonstrated that measured pressure head by a human finger was between 3-4kPa, which is sufficient to power fluids for various microfluidic applications, such as point-of-care diagnostics. INTRODUCTION in need of urgent medical diagnostics such as in the battle fields or technological disadvantaged regions often miss the opportunities of being treated promptly due to the requirement of bulky, complex and time-consuming medical instruments. Chip-based microfluidics has the potential to solve some of these problems and make contributions in scientific study such as cellular characterizations (1) as well as in medical applications for quick point-of-care diagnostics (2). In the state-of-the-art microfluidic devices, one or more bulky and power-hungry syringe pumps are required and it has been a bottleneck in moving chip-scale microfluidics system to practical market places. Therefore, researchers in both academic and industrial labs have been interested in developing low-cost, low-power, and portable micropumps. For example, several groups have previously attempted simple methodologies to pump microfluidics with minimum power consumption such as the application of capillary force on polydimethylsiloxane (PDMS) (3,4) and paper (5,6) as well as the water-powered osmotic actuators and pumps (7,8). Unfortunately, the magnitude of capillary force is restricted and osmotic actuation is slow such that these methodologies can be applied only to limited microfluidics systems. In this paper, we propose a concept of a versatile 'human-powered' fluid pumps as a modular element to provide pressure head for a variety of microfluidic systems. Figure 1 illustrates the basic concept of the finger-powered pump with the demonstration in pumping fluids into a microfluidic chip at the bottom. The finger-powered pump has a deformable chamber which can be activated by a human finger (i.e. pushed by a finger) to infuse solutions out of the pump chamber to the target microfluidic chip. Inlet and outlet are connected with microchannels and various fluidic components. For example, a passive flow rate regulator can be integrated to regulate the flow rate and other passive or active elements can be further integrated into the system. Furthermore, the manufacturing cost is expected to be low as molding and low-cost materials are utilized in the manufacturing process. As such, it is believed that these low-cost, portable and easy-to-operate microfluidic pumps could be promising in practical applications of microfluidic technologies including point-of-care diagnostics.

‘Human-powered’ microdroplet generators are ideal for droplet-based point-of-care diagnostics applications. Here we present a versatile ‘finger-powered’ microdroplet generator. The prototype system was fabricated via polymer-based micromachining processes. In this work, we have achieved: (1) the use of a human finger as the actuation force for droplet generation, (2) an integrated pumping system for actuating both droplet and solvent fluids simultaneously,

ABSTRACT A continuous flow, microfluidic railing system has been developed for the rapid and autonomous exchanges of bead and bead-in-droplet formations. Fluidic encapsulations of microparticles (e.g., microbeads and living cells) inside individual microdroplets provide various possibilities for chemical and biological applications. This work extends the bead-in-droplet technology from a single type droplet to a multiple-stage, different droplet solutions system. A micropost array railing system has been demonstrated to passively: (i) guide an array of bead-in-droplet in a “first” droplet solution to different liquid flows and release the microbeads from the droplets, and (ii) re-encapsulate the released microbeads in droplets containing a different, “second” droplet solution. Experimental results revealed successful continuous flow solution exchanges for water-in-oil droplets with size of about 60.2μm in diameter containing microbeads of 15μm in diameter.

A lithography-free microchannel fabrication process with controlled pattern is demonstrated via the combination of Near Field Electrospinning (NFES) and molding of polydimethysiloxane (PDMS). Electrospun polymer fibers (1-10μm in width, 0.5-4μm in height) were patterned onto a silicon substrate to serve as the template. Microfluidic devices with parallel and grid-pattern microchannels were created and tested. By adjusting the electrospinning parameters, control

This paper demonstrates the feasibility in utilizing microtopographic substrates to maintain or inhibit collective cell behavior via micromachined posts and thin-film stencils. This technique enables groups, or collectives, of cells to be localized and directly cultured onto microposts for studying effects of substrate stiffness on collective cell behavior. Preliminary results show that bovine aortic endothelial cells (BAECs) collectively contract on

ABSTRACT Microfluidic droplet-based microreactors offer significant advantages for the synthesis of nanoparticles, including high control of reagent loading and mixing. One limitation, however, is that retrieving synthesized nanoparticles from microdroplets typically requires laborious and time-consuming “off-chip” procedures (e.g., droplet collection, centrifugication and nanoparticle resuspension). To bypass these issues, here we introduce a continuous flow microfluidic system to enable the rapid and autonomous droplet-based generation and retrieval of nanoparticles. Specifically, we utilize a micropost array railing technique in order to passively: (i) generate microdroplets in which nanoparticles are synthesized, (ii) guide the particle-containing droplets into an oil-phase wash solution (i.e., to remove surfactant), and (iii) “lyse” the microdroplets to release the nanoparticles into the water flow. Experimental results demonstrated the successful synthesis and retrieval of magnetic iron-oxide nanoparticles, which can be employed for applications including bioseparation, biotagging and imaging.

Point-of-care (POC) and disposable biomedical applications demand low-power microfluidic systems with pumping components that provide controlled pressure sources. Unfortunately, external pumps have hindered the implementation of such microfluidic systems due to limitations associated with portability and power requirements. Here, we propose and demonstrate a 'finger-powered' integrated pumping system as a modular element to provide pressure head for a variety of advanced microfluidic applications, including finger-powered on-chip microdroplet generation. By utilizing a human finger for the actuation force, electrical power sources that are typically needed to generate pressure head were obviated. Passive fluidic diodes were designed and implemented to enable distinct fluids from multiple inlet ports to be pumped using a single actuation source. Both multilayer soft lithography and injection molding processes were investigated for device fabrication and performance. Experimen...

The ability to achieve multi-layer synthesis on the surface of microbeads is critical for diverse chemical and biological assays. Although microfluidic techniques for layer-by-layer (LbL) synthesis have been demonstrated for droplets, accomplishing continuous flow multi-layer synthesis for microbeads has remained a significant challenge. Here we present a micropost array railing (µPAR) system to achieve continuous flow LbL functionalization on microbead