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Metal-organic frameworks (MOFs) have attracted considerable attention as novel nanoporous materials that combine the properties of organic and inorganic porous materials. HKUST-1 is one of the most well-developed and representative MOFs with wide applications in gas storage and separation, adsorption, and capture. In this study, we used microfluidics, an advanced technique of manipulation of small fluid volumes in microscale or even nanoscale channels, to investigate the effect of sodium dodecyl sulfate (SDS) on the growth of HKUST-1 crystals. We directly observed the morphological evolution of HKUST-1 crystals through droplet arrays with the SDS concentration gradient. The morphology of HKUST-1 evolved from cubic to cuboctahedron and finally to octahedron with increasing SDS concentration. The study results demonstrated the important role played by anions in solution in the structural regulation of HKUST-1.

A microheater and a thermal sensor were fabricated inside elastomeric polydimethylsiloxane microchannels by injecting silver paint (or other conductive materials) into the channels. With a high-precision control scheme, microheaters can be used for rapid heating, with precise temperature control and uniform thermal distribution. Using such a microheater and feedback system, a polymerase chain reaction experiment was carried out whereas the DNA was successfully amplified in 25 cycles, with 1 min per cycle.

A novel microfluidic pressure sensor which can be fully integrated into polydimethylsiloxane (PDMS) is reported. The sensor produces electrical signals directly. We integrated PDMS-based conductive composites into a 30 mum thick membrane and bonded it to the microchannel side wall. The response time of the sensor is approximately 100 ms and can work within a pressure range as wide as 0-100 kPa. The resolution of this micropressure sensor is generally 0.1 kPa but can be increased to 0.01 kPa at high pressures as a result of the quadratic relationship between resistance and pressure. The PDMS-based nature of the sensor ensures its perfect bonding with PDMS chips, and the standard photolithographic process of the sensor allows one-time fabrication of three dimensional structures or even microsensor arrays. The theoretical calculations are in good agreement with experimental observations.