Changlin Pang

Ion liquid chromatography on-a-chip with beads-packed parylene column

A parylene-MEMS ion-exchange Liquid Chromatography (LC) chip is presented here. The chip is integrated with microfluidic I/O ports, a separation column, frits/filters, and a conductivity detector. The column is packed with conventional LC stationary phase support materials, i.e. micro-beads with surface functional groups. To withstand high pressure normally encountered in high performance liquid chromatography (HPLC), a self-aligned, channel-anchoring technique is developed to increase the pressure rating of the parylene microfluidic devices from 30 to at least 800psi. On-chip injection, separation and detection of anions in water, with /spl sim/25 ppm concentration, have been successfully demonstrated. To our knowledge, this is the first demonstration of microbeads-packed column ion liquid Chromatography (LC) on a chip.

Integrated parylene-cabled silicon probes for neural prosthetics

Recent advances in the field of neural prosthetics have demonstrated the thought control of a computer cursor. This capability relies primarily on electrode array surgically implanted into the brain as an acquisition source of neural activity. Various technologies have been developed for signal extraction; however most suffer from either fragile electrode shanks and bulky cables or inefficient use of surgical site areas. Here we present a design and initial testing results from high electrode density, silicon based arrays system with an integrated parylene cable. The greatly reduced flexible rigidity of the parylene cable is believed to relief possible mechanical damages due to relative motion between a brain and its skull.

An integrated LC-ESI chip with electrochemical-based gradient generation

This work reports the first on-chip generation of gradient elution using electrochemical pumping, for application in Liquid Chromatography-Electrospray Ionization (LC-ESI). The system consists of Parylene, SU-8 and PDMS parts to create two 3 /spl mu/L on-chip solvent reservoirs, two electrochemical pumps and an ESI nozzle. Pumping is controlled galvanostatically (i.e., through electrolysis current). At low back pressures, pumping rate can reach 200 nL/min using just 40 /spl mu/A (power consumption <100 /spl mu/W). At 80 psi, 200 /spl mu/A (power consumption <1 mW) is sufficient to deliver fluid at 75 nL/min. Higher electrical currents have been used to increase the flow rate or to achieve pumping at higher back pressures. For example, pumping at 200 psi back pressure has been demonstrated using a current of 800 /spl mu/A. Electrically controlled on-chip gradient generation is achieved without any external fluidic connections to the chip. Continuous generation of gradients for 30 minutes at a total flow rate of /spl sim/100 nL/min is also realized and confirmed with mass spectroscopy (MS) measurements. The developed on-chip gradient generation system meets the general requirements of LC applications.