Limits...
Sequential push-pull pumping mechanism for washing and evacuation of an immunoassay reaction chamber on a microfluidic CD platform.

Thio TH, Ibrahim F, Al-Faqheri W, Soin N, Kahar Bador M, Madou M - PLoS ONE (2015)

Bottom Line: However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps.The proposed technique is demonstrated on two CD designs.The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Centre for Innovation in Medical Engineering, Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Faculty of Science, Technology, Engineering and Mathematics, INTI International University, Persiaran Perdana BBN, Putra Nilai, 71800 Nilai, Negeri Sembilan, Malaysia.

ABSTRACT
A centrifugal compact disc (CD) microfluidic platform with reservoirs, micro-channels, and valves can be employed for implementing a complete immunoassay. Detection or biosensor chambers are either coated for immuno-interaction or a biosensor chip is inserted in them. On microfluidic CDs featuring such multi-step chemical/biological processes, the biosensor chamber must be repeatedly filled with fluids such as enzymes solutions, buffers, and washing solutions. After each filling step, the biosensor chamber needs to be evacuated by a passive siphoning process to prepare it for the next step in the assay. However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps. In this work, a unique thermo-pneumatic (TP) Push-Pull pumping method is employed to provide a superior alternative biosensor chamber filling and evacuation technique. The proposed technique is demonstrated on two CD designs. The first design features a simple two-step microfluidic process to demonstrate the evacuation technique, while the second design shows the filling and evacuation technique with an example sequence for an actual immunoassay. In addition, the performance of the filling and evacuation technique as a washing step is also evaluated quantitatively and compared to the conventional manual bench top washing method. The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber. Furthermore, by addressing the issue of rotational speed dependency and limited space concerns in implementing repetitive filling and evacuation steps, this newly introduced technique increases the flexibility of the microfluidic CD platform to perform multi-step biological and chemical processes.

No MeSH data available.


Evacuation, wash, and rinse using push-wash and pull-evacuation.(a) Sequence of steps for the evacuation of a biosensor chamber using pull-evacuation. (b) Sequence of steps for the washing of an empty biosensor chamber using a push-wash followed by a pull-evacuation. (c) Sequence of steps for rinsing a non-empty biosensor chamber with a partial push-wash following by a pull-evacuation.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4390340&req=5

pone.0121836.g003: Evacuation, wash, and rinse using push-wash and pull-evacuation.(a) Sequence of steps for the evacuation of a biosensor chamber using pull-evacuation. (b) Sequence of steps for the washing of an empty biosensor chamber using a push-wash followed by a pull-evacuation. (c) Sequence of steps for rinsing a non-empty biosensor chamber with a partial push-wash following by a pull-evacuation.

Mentions: A TP air chamber connected to a liquid chamber allows for push pumping of liquid out of a liquid chamber. Push-wash takes place when the TP air chamber is being heated thus expanding the air and pushing washing liquid out from the liquid chamber into an adjoining chamber. A liquid chamber, an empty waste chamber, and a TP air chamber that are interconnected in series allows also for pull pumping of liquid from the liquid chamber into the empty waste chamber. Pull-evacuation takes place when a preheated TP air chamber is cooled down, and contracting air then pulls the liquid from the liquid chamber into the adjoining waste chamber, thus evacuating the liquid chamber. This washing and evacuation process can be performed over and over. In Fig 3 we illustrate the sequence of steps for an evacuation, a wash, and a rinse. The CD design in Fig 3 consists of a biosensor chamber, wash solution chamber, waste chamber, and two TP air chambers. Each process starts with a blue liquid in the wash solution chamber C, and a red liquid in biosensor chamber B. The TP air chamber (T-C) contains a venting hole while the TP air chamber (T-W) is sealed. Heat is assumed to be applied uniformly over both TP air chambers when actuated.


Sequential push-pull pumping mechanism for washing and evacuation of an immunoassay reaction chamber on a microfluidic CD platform.

Thio TH, Ibrahim F, Al-Faqheri W, Soin N, Kahar Bador M, Madou M - PLoS ONE (2015)

Evacuation, wash, and rinse using push-wash and pull-evacuation.(a) Sequence of steps for the evacuation of a biosensor chamber using pull-evacuation. (b) Sequence of steps for the washing of an empty biosensor chamber using a push-wash followed by a pull-evacuation. (c) Sequence of steps for rinsing a non-empty biosensor chamber with a partial push-wash following by a pull-evacuation.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390340&req=5

pone.0121836.g003: Evacuation, wash, and rinse using push-wash and pull-evacuation.(a) Sequence of steps for the evacuation of a biosensor chamber using pull-evacuation. (b) Sequence of steps for the washing of an empty biosensor chamber using a push-wash followed by a pull-evacuation. (c) Sequence of steps for rinsing a non-empty biosensor chamber with a partial push-wash following by a pull-evacuation.
Mentions: A TP air chamber connected to a liquid chamber allows for push pumping of liquid out of a liquid chamber. Push-wash takes place when the TP air chamber is being heated thus expanding the air and pushing washing liquid out from the liquid chamber into an adjoining chamber. A liquid chamber, an empty waste chamber, and a TP air chamber that are interconnected in series allows also for pull pumping of liquid from the liquid chamber into the empty waste chamber. Pull-evacuation takes place when a preheated TP air chamber is cooled down, and contracting air then pulls the liquid from the liquid chamber into the adjoining waste chamber, thus evacuating the liquid chamber. This washing and evacuation process can be performed over and over. In Fig 3 we illustrate the sequence of steps for an evacuation, a wash, and a rinse. The CD design in Fig 3 consists of a biosensor chamber, wash solution chamber, waste chamber, and two TP air chambers. Each process starts with a blue liquid in the wash solution chamber C, and a red liquid in biosensor chamber B. The TP air chamber (T-C) contains a venting hole while the TP air chamber (T-W) is sealed. Heat is assumed to be applied uniformly over both TP air chambers when actuated.

Bottom Line: However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps.The proposed technique is demonstrated on two CD designs.The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Centre for Innovation in Medical Engineering, Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Faculty of Science, Technology, Engineering and Mathematics, INTI International University, Persiaran Perdana BBN, Putra Nilai, 71800 Nilai, Negeri Sembilan, Malaysia.

ABSTRACT
A centrifugal compact disc (CD) microfluidic platform with reservoirs, micro-channels, and valves can be employed for implementing a complete immunoassay. Detection or biosensor chambers are either coated for immuno-interaction or a biosensor chip is inserted in them. On microfluidic CDs featuring such multi-step chemical/biological processes, the biosensor chamber must be repeatedly filled with fluids such as enzymes solutions, buffers, and washing solutions. After each filling step, the biosensor chamber needs to be evacuated by a passive siphoning process to prepare it for the next step in the assay. However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps. In this work, a unique thermo-pneumatic (TP) Push-Pull pumping method is employed to provide a superior alternative biosensor chamber filling and evacuation technique. The proposed technique is demonstrated on two CD designs. The first design features a simple two-step microfluidic process to demonstrate the evacuation technique, while the second design shows the filling and evacuation technique with an example sequence for an actual immunoassay. In addition, the performance of the filling and evacuation technique as a washing step is also evaluated quantitatively and compared to the conventional manual bench top washing method. The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber. Furthermore, by addressing the issue of rotational speed dependency and limited space concerns in implementing repetitive filling and evacuation steps, this newly introduced technique increases the flexibility of the microfluidic CD platform to perform multi-step biological and chemical processes.

No MeSH data available.