Amperometric Detection of Carbohydrates with a Portable Silicone/Quartz Capillary Microchip by Designed Fracture Sampling

On-chip electrochemical detection of glucose towards the miniaturised quality control of carbohydrate-based radiotracers

We have developed two microfluidic platforms for the electrochemical detection of glucose, using either a screen-printed electrode or wire electrodes, towards the quality control testing of carbohydrate-based radiotracers used in medical imaging.

Nanofracture on fused silica microchannel for Donnan exclusion based electrokinetic stacking of biomolecules

Due to Donnan exclusion, charged molecules are prohibited from passing through a channel of electrical double layer scale (nanometers), even though the molecules are smaller than the lowest dimension of the channel. To employ this effect for on-chip pre-concentration, an ion channel of nanometer scale has to be introduced. Here we introduced a simple method of generating a fracture (11-250 nm) directly on the commercially available open tubular fused silica capillary, and a chip comprised of the capillary with the nanofracture was prepared. A ring-disk model of the fracture was derived with which the fracture width can be easily characterized online without any damage to the chip, and the result was validated by a scanning electron microscope (SEM). The fractures can be used directly as a nanofluidic interface exhibiting an obvious ion concentration polarization effect with high current flux. On-chip electrokinetic stacking of SYBR Green I labeled λDNA inside the capillary was successfully demonstrated, and a concentration factor close to the amplification rate of the polymerase chain reaction (PCR) was achieved within 7 min. The chip is inexpensive and easy to prepare in common chemistry and biochemistry laboratories without limitations in expensive microfabrication facilities and sophisticated expertise. More applications of this interface could be found for enhancing the detectability of capillary based microfluidic analytical systems for the analysis of low concentrated charged species.

Hybrid integrated PDMS microfluidics with a silica capillary

To harness the properties of both PDMS and silica, we have demonstrated hybrid integrated PDMS microfluidic systems with fused silica capillaries. The hybrid integrated PDMS microfluidics and silica capillary (iPSC) modules exhibit a novel architecture and method for leakage free CE sample injection merely requiring a single high voltage source and one pair of electrodes. The use of the iPSC device is based on a modular approach which allows the capillary to be reused extensively whilst replacing the attached fluidic module for different experiments. Integrating fused silica capillaries with PDMS microfluidic modules allows the direct application of a wide variety of well established conventional CE protocols for separations of complex analytes. Furthermore it bears the potential for facile coupling to standard electro-spray ionization mass spectrometry (ESI-MS), letting users focus on the sample analysis rather than the development of new separation protocols. The fabrication of the iPSC module consists of a simple and quick three-step method that submerges a fused silica capillary in PDMS prepolymer. After cross linking the prepolymer and punching the inlets, the iPSC module layer can be mounted onto a microfluidic device for CE separation.