Optofluidic lasers are an emerging technology for the development of miniaturized light sources and biological and chemical sensors. However, most optofluidic lasers demonstrated to date are operated at the single optical cavity level, which limits their applications in high-throughput biochemical sensing, high-speed wavelength switching, and on-chip spectroscopic analysis. Here, we demonstrated an optofluidic droplet laser array on a silicon chip with integrated microfluidics, in which four individual droplet optical cavities are generated and controlled by a 2 × 2 nozzle array. Arrays of droplets with a diameter ranging from 115 to 475 μm can be generated, removed, and regenerated on demand. The lasing threshold of the droplet laser array is in the range of 0.63–2.02 μJ/mm2. An image-based lasing threshold analysis method is developed, which enables simultaneous lasing threshold measurement for all laser units within the laser array using a low-cost camera. Compared to the conventional spectrum-based threshold analysis method, the lasing threshold obtained from the image-based method showed consistent results. Our droplet laser array is a promising technology in the development of cost-effective and integrated coherent light source on a chip for point-of-care applications.

We report here a compact vapor sensor based on polymer coated two-dimensional (2D) defect-free photonic crystal slabs (PCS). The sensing mechanism is based on the resonance spectral shift associated with the Fano resonance mode in the PCS due to the vapor molecule adsorption and desorption induced changes in both polymer thickness and polymer refractive index (RI). Sensitivity due to RI and thickness change were theoretically investigated respectively. With three different thicknesses of OV-101 polymer coating, sensitivity and response time were experimentally evaluated for hexane and ethanol vapors. The polymer demonstrated roughly four times higher sensitivity towards the hexane vapor than ethanol vapor. The PCS sensor with thicker polymer coating showed higher sensitivity to both hexane and ethanol vapors but exhibiting longer response time.

This work presents a new class of micromachined electrostatic actuators capable of producing output force and displacement unprecedented for MEMS electrostatic actuators. The actuators feature submicron high aspect ratio transduction gaps lined up in two-dimensional arrays. Such an arrangement of microscale actuator cells allows the addition of force and displacements of a large number of cells (up to 7600 in one demonstrated array), leading to displacements ranging in the hundreds of microns and several gram forces of axial force. For 50 µm thick actuators with horizontal dimensions in the 1–4 millimeter range, an out-of-plane displacement of up to 678 µm at 46 V, a bending moment of up to 2.0 µNm, i.e., 0.08 N (~8 gram-force) of axial force over a 50 µm by 2 mm cross-sectional area of the actuator (800 kPa of electrostatically generated stress), and an energy density (mechanical work output per stroke per volume) up to 1.42 mJ/cm3 was demonstrated for the actuators.

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