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(J.C. Carter). AbstractWe demonstrate the feasibility of using Drop-on-Demand microjet printing technology for fabricating imaging sensors by reproducibly printing an array of photopolymerizable sensing elements, containing a pH sensitive indicator, on the surface of an optical fiber image guide. The reproducibility of the microjet printing process is excellent for microdot (i.e. micron-sized polymer) sensor diameter (92.2±2.2 microns), height (35.0±1.0 microns), and roundness (0.00072 ± 0.00023). pH sensors were evaluated in terms of pH sensing ability (≤2% sensor variation), response time, and hysteresis using a custom fluorescence imaging system. In addition, the microjet technique has distinct advantages over other fabrication methods, which are discussed in detail.

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The microjet printing method is being used to fabricate microlens arrays for use in massively parallel, VCSELbased datacom switches and to deposit lenslets of various configurations onto the tips of single-mode telecom fibers. Applications in the latter case include collimation ofthe output beams for free space optical interconnection and increasing the fiber numerical aperture for collection of light from edge-emitting diode lasers. Additional applications ofthis technology include printing of arrays of active sensor elements onto the tips of imaging fiber bundles and fabrication of microlenses with axial index of refraction gradients to reduce focal spot size, utilizing multiple print heads with differing fluids. This low-cost, data-driven process, based on "dropon-demand" inkjet technology, involves the dispensing and placing of precisely sized microdroplets of optical material onto optical substrates. The micro-optical elements are printed with 100% solid, UV-curing optical epoxies, utilizing printing devices that can dispense picoliter-volume droplets at temperatures up to 300°C.