Synthesis and Electronic Properties of Individual Single-Walled Carbon Nanotube/Polypyrrole Composite Nanocables

release during PIPAAm collapse. This burst is analogous to drug release from collapsing PIPAAm gel disks undergoing analogous thermal treatment. Similarly, just after each temperature return to 30 °C, small fluores-cent spikes are observed. In contrast, oscillatory fluorescent changes have been observed using 0.5 min cyclic intervals (shown in Fig. 3c) indicating subtle PIPAAm swell–shrink transition kinetics affecting flow profiles. Aqueous flow has been blocked completely using air bubbles in PIPAAm-grafted capillaries ( = 200 lm) above the PIPAAm transition temperature, where the microchannel surfaces are hydrophobic, trapping the air bubble. Our microfluidic channels distinguish their flow-control behavior by completely blocking water flow via PIPAAm graft hydration. Considerably higher pressure is required to initiate water flow through PIPAAm-grafted capillaries below PIPAAm’s collapse-transition temperature. Thermally regulated flow control in PIPAAm-grafted capillaries is rapid and reversible, facilitating many reliable and repeated open–close cycles. Such reversible, thermally modulated, polymer-grafted on–off switches for controlling microfluidic behavior might be regulated locally on-chip using optical signals (local infrared heating), resistive heating microelements, or external thermostats. Spatial control is possible using patterned grafted capillaries and different polymergrafted areas with chemistries exhibiting distinct phase-transition behavior in designated locations. Opportunities for new microvalve systems exploiting this basic design are substantial.