A new methodology for the development of miniature photoacoustic trace gas sensors using 3D printing is presented. A near-infrared distributed feedback (DFB) laser is used together with a polymer-based gas cell, off-the-shelf fiber optic collimators, and a microelectromechanical system (MEMS) microphone to measure acetylene at 1532.83 nm. The resonance behavior of the miniature gas cell is analyzed using a theoretical and experimental approach, with a measured resonance frequency of 15.25 kHz and a Q-factor of 15. A minimum normalized noise equivalent absorption of 4.5×10(-9)  W cm(-1) Hz(-1/2) is shown together with a 3σ detection limit of 750 parts per billion (ppb) for signal averaging times of 35 s. The fiber-coupled delivery and miniature cost-effective cell design allows for use in multipoint and remote detection applications.

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T-gates are commonly used in high frequency low noise transistors on III–V materials since they provide a combination of short gate length and low gate resistance. Nanoimprint lithography can produce minimum pattern feature sizes equivalent to those attainable by high resolution electron beam lithography and it has potential advantages in terms of speed and cost. The imprint lithography step must be reliable and compatible with existing device process flows. In this article we describe a bilayer resist imprinting procedure for the fabrication of 120 nm T-gates for high electron mobility transistors. The results of transistor dc characterization are also presented and are similar to those obtained for transistors fabricated on the same material with gates realized by electron beam lithography.

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