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Deterministic bead-in-droplet ejection utilizing an integrated plug-in bead dispenser for single bead – based applications

View Article: PubMed Central - PubMed

ABSTRACT

This paper presents a deterministic bead-in-droplet ejection (BIDE) technique that regulates the precise distribution of microbeads in an ejected droplet. The deterministic BIDE was realized through the effective integration of a microfluidic single-particle handling technique with a liquid dispensing system. The integrated bead dispenser facilitates the transfer of the desired number of beads into a dispensing volume and the on-demand ejection of bead-encapsulated droplets. Single bead–encapsulated droplets were ejected every 3 s without any failure. Multiple-bead dispensing with deterministic control of the number of beads was demonstrated to emphasize the originality and quality of the proposed dispensing technique. The dispenser was mounted using a plug-socket type connection, and the dispensing process was completely automated using a programmed sequence without any microscopic observation. To demonstrate a potential application of the technique, bead-based streptavidin–biotin binding assay in an evaporating droplet was conducted using ultralow numbers of beads. The results evidenced the number of beads in the droplet crucially influences the reliability of the assay. Therefore, the proposed deterministic bead-in-droplet technology can be utilized to deliver desired beads onto a reaction site, particularly to reliably and efficiently enrich and detect target biomolecules.

No MeSH data available.


Related in: MedlinePlus

Optimization test result for trapping single bead.At various negative pressures in the dispensing reservoir and positive pressures on the pneumatic valve, the number of trapped beads was observed 20 times under each condition. NP indicates negative pressure. Black-empty, red-solid, blue-solid, and magenta-solid bars indicate 0, 1, 2, and 3 beads, respectively.
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f3: Optimization test result for trapping single bead.At various negative pressures in the dispensing reservoir and positive pressures on the pneumatic valve, the number of trapped beads was observed 20 times under each condition. NP indicates negative pressure. Black-empty, red-solid, blue-solid, and magenta-solid bars indicate 0, 1, 2, and 3 beads, respectively.

Mentions: The operating conditions for trapping and releasing single beads were optimized to ensure that only a single bead reached the loading site. According to reported experimental results20, trapping of a single bead can be achieved by controlling the width of the trapping stream at the branch point and the trapping space. In the present experiment, the trapping stream was regulated by controlling the pressures applied to the inlet, outlet, and dispensing reservoirs. Pressures were set to 2 and 1.2 kPa at the inlet and outlet, respectively, to minimize the consumption of the bead suspension and to prevent beads from sinking to the bottom of the inlet reservoir and the plug channel. In the dispensing reservoir, a negative pressure was normally applied to retract the residual liquid into the nozzle in order to prevent the wetting of the nozzle after droplet ejection and to efficiently attract released beads from the trap to the loading site. To experimentally optimize the trapping stream, the amplitude of the negative pressure was varied from −0.4 to −2.0 kPa. The maximum amplitude was limited to −2 kPa because at higher amplitudes, the meniscus of the liquid at the distal end of the nozzle retracts, trapping bubbles in the dispenser. Such trapped bubbles could induce malfunctions in each operation mode by altering the hydraulic resistances in the channels where the bubbles are trapped. Next, the trapping space was regulated by deflecting the pneumatic valve; this deflection is dependent on the magnitude of the applied positive pressure. The number of trapped beads at various negative pressures in the dispensing reservoir and positive pressures on the pneumatic valve was analyzed (Fig. 3).


Deterministic bead-in-droplet ejection utilizing an integrated plug-in bead dispenser for single bead – based applications
Optimization test result for trapping single bead.At various negative pressures in the dispensing reservoir and positive pressures on the pneumatic valve, the number of trapped beads was observed 20 times under each condition. NP indicates negative pressure. Black-empty, red-solid, blue-solid, and magenta-solid bars indicate 0, 1, 2, and 3 beads, respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5385560&req=5

f3: Optimization test result for trapping single bead.At various negative pressures in the dispensing reservoir and positive pressures on the pneumatic valve, the number of trapped beads was observed 20 times under each condition. NP indicates negative pressure. Black-empty, red-solid, blue-solid, and magenta-solid bars indicate 0, 1, 2, and 3 beads, respectively.
Mentions: The operating conditions for trapping and releasing single beads were optimized to ensure that only a single bead reached the loading site. According to reported experimental results20, trapping of a single bead can be achieved by controlling the width of the trapping stream at the branch point and the trapping space. In the present experiment, the trapping stream was regulated by controlling the pressures applied to the inlet, outlet, and dispensing reservoirs. Pressures were set to 2 and 1.2 kPa at the inlet and outlet, respectively, to minimize the consumption of the bead suspension and to prevent beads from sinking to the bottom of the inlet reservoir and the plug channel. In the dispensing reservoir, a negative pressure was normally applied to retract the residual liquid into the nozzle in order to prevent the wetting of the nozzle after droplet ejection and to efficiently attract released beads from the trap to the loading site. To experimentally optimize the trapping stream, the amplitude of the negative pressure was varied from −0.4 to −2.0 kPa. The maximum amplitude was limited to −2 kPa because at higher amplitudes, the meniscus of the liquid at the distal end of the nozzle retracts, trapping bubbles in the dispenser. Such trapped bubbles could induce malfunctions in each operation mode by altering the hydraulic resistances in the channels where the bubbles are trapped. Next, the trapping space was regulated by deflecting the pneumatic valve; this deflection is dependent on the magnitude of the applied positive pressure. The number of trapped beads at various negative pressures in the dispensing reservoir and positive pressures on the pneumatic valve was analyzed (Fig. 3).

View Article: PubMed Central - PubMed

ABSTRACT

This paper presents a deterministic bead-in-droplet ejection (BIDE) technique that regulates the precise distribution of microbeads in an ejected droplet. The deterministic BIDE was realized through the effective integration of a microfluidic single-particle handling technique with a liquid dispensing system. The integrated bead dispenser facilitates the transfer of the desired number of beads into a dispensing volume and the on-demand ejection of bead-encapsulated droplets. Single bead–encapsulated droplets were ejected every 3 s without any failure. Multiple-bead dispensing with deterministic control of the number of beads was demonstrated to emphasize the originality and quality of the proposed dispensing technique. The dispenser was mounted using a plug-socket type connection, and the dispensing process was completely automated using a programmed sequence without any microscopic observation. To demonstrate a potential application of the technique, bead-based streptavidin–biotin binding assay in an evaporating droplet was conducted using ultralow numbers of beads. The results evidenced the number of beads in the droplet crucially influences the reliability of the assay. Therefore, the proposed deterministic bead-in-droplet technology can be utilized to deliver desired beads onto a reaction site, particularly to reliably and efficiently enrich and detect target biomolecules.

No MeSH data available.


Related in: MedlinePlus