a) Photograph of the actual microfluidic device. b) Micrograph of the device in action. A pyrrole solution (flow rate: 1.0 µL min⁻¹) was first injected into the device, and two pairs of sheath streams (flow rate: 30 µL min⁻¹) were employed to compress the pyrrole solution in sequence to generate a 2-µm-wide hydrodynamically focused laminar stream. To help visualize the flow characteristics, food dye was dissolved in the pyrrole solution. c) The 2-µm-wide focused laminar steam served as a dynamic template for deposition of a 1-µm-wide Ppy micropattern across a 10-µm microelectrode junction gap where a constant current (200 nA) was applied. d) Scanning electron microscopy (SEM) image of the 1-µm-wide Ppy micropattern across a Pt electrode pair.

a) Real-time resistance responses (R) of a binary sensor composed of a Ppy- and a COOH-Ppy-based micropattern electrode junction upon periodic exposure to a library of saturated organic vapors (each 20 µL in volume). b) Scatter plot summarizing the collective sensing responses to individual organic vapors. EA=ethyl acetate.

a) A laminar interface generated between two miscible fluid streams can serve as a flowing template for continuous micropatterning in a fluidic channel. b) A hydrodynamically focused laminar stream produced in a new type of microfluidic setup can be employed as a dynamic template for site-specific electrochemical deposition of size-controllable CP micropatterns across individually addressable electrode junction pairs.

a) Plots of potential (E) versus time (t) for electrochemical deposition of Ppy micropatterns across the respective 10-µm electrode gaps in the presence of 2, 5, and 10-µm-wide focused streams. b) Optical micrographs (right) of the applied focused streams and SEM images (left) of the resulting Ppy micropatterns.