Simple and reusable picoinjector for liquid delivery via nanofluidics approach

Shunbo Li,Wenbin Cao,Yu Sanna Hui,Weijia Wen

doi:10.1186/1556-276x-9-147

Abstract

Precise control of sample volume is one of the most important functions in lab-on-a-chip (LOC) systems, especially for chemical and biological reactions. The common approach used for liquid delivery involves the employment of capillaries and microstructures for generating a droplet which has a volume in the nanoliter or picoliter range. Here, we report a novel approach for constructing a picoinjector which is based on well-controlled electroosmotic (EO) flow to electrokinetically drive sample solutions. This picoinjector comprises an array of interconnected nanochannels for liquid delivery. Such technique for liquid delivery has the advantages of well-controlled sample volume and reusable nanofluidic chip, and it was reported for the first time. In the study of the pumping process for this picoinjector, the EO flow rate was determined by the intensity of the fluorescent probe. The influence of ion concentration in electrolyte solutions over the EO flow rate was also investigated and discussed. The application of this EO-driven picoinjector for chemical reactions was demonstrated by the reaction between Fluo-4 and calcium chloride with the reaction cycle controlled by the applied square waves of different duty cycles. The precision of our device can reach down to picoliter per second, which is much smaller than that of most existing technologies. This new approach, thus, opens further possibilities of adopting nanofluidics for well-controlled chemical reactions with particular applications in nanoparticle synthesis, bimolecular synthesis, drug delivery, and diagnostic testing.PACS85.85.+ j; 87.15.hj; 82.39.Wj

Highlights

Precise control of the sample volume is the first prerequisite in high-resolution micro total analysis systems and microreactors [1,2,3]
In order to obtain the linear relationship of the fluorescent intensity of Fluorescein isothiocyanate isomer I (FITC) to the dye concentration, images of microchannel filling with solutions of different dye concentrations from 0.3 to 30 nM were taken and analyzed
We have demonstrated that a simple nanofluidic device fabricated on a Si wafer with a thin layer of SiO2 and sealed by a PDMS thin film has its potential for constructing a picoinjector

Summary

Introduction

Precise control of the sample volume is the first prerequisite in high-resolution micro total analysis systems (μTAS) and microreactors [1,2,3]. Electroosmotic pumps [13], based on electrokinetics and operated with no moving part, are a better way for liquid delivery since they are much easier to integrate in μTAS than the piezoelectric method They are driven by electroosmosis (EO) which arises from the existence of an electrical double layer at the solid-liquid interface and holds great promise in generating fluid flow in nanochannels under the influence of an electric field. Potential applications based on this picoinjector include precisely controlled chemical reactions [15], drug delivery [16], as well as biomolecular translocation [17] All of these applications are based on the variation of the applied voltage bias across nanopores or nanochannels

Methods

Results

Conclusion