Article

# In vivo Clinical and Intravital Imaging with MEMS Based Dual-Axes Confocal Microscopes

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## Abstract

We demonstrate microelectromechanical systems (MEMS) based near infrared fluorescence dual-axes confocal (DAC) microscopes in both a 10-mm microscope and a 5-mm endoscope for three-dimensional (3-D) cellular imaging of both ex vivo and in vivo samples.

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In this paper, we introduce a 2-D microelectromechanical systems scanner for 3.2-mm-diameter dual-axis confocal microendoscopes, fabricated exclusively by front-side processing. Compared to conventional bulk micromachining that incorporates back-side etching, the front-side process is simple and thus enables high device yield. By eliminating the back-side etch window, the process yields compact and robust structures that facilitate handling and packaging. An important component of our front-side fabrication is a low-power deep reactive ion etching (DRIE) process that avoids the heating problems associated with standard DRIE. Reducing the RF etch coil power from 2400 to 1500 W leads to elimination of the spring disconnection problem caused by heat-induced aggressive local etching. In our scanner, the outer frame of the gimbal is split and noncontinuous to allow the scanner to be diced along the very edge of the scanning mirror in order to minimize the chip size (1.8 mm $\times$ 1.8 mm). The maximum optical deflection angles in static mode are $\pm 5.5^{\circ}$ and $\pm 3.8^{\circ}$ for the outer and inner axes, respectively. In dynamic operation, the optical deflection angles are $\pm 11.8^{\circ}$ at 1.18 kHz for the outer axis and $\pm 8.8^{\circ}$ at 2.76 kHz for the inner axis. $\hfill$[2011-0217]
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We present a 2-D MEMS scanner for 3.2mm-diameter dual-axis confocal microendoscopes, which is fabricated by only front-side processing. Frontside-only processing greatly simplifies the process and reduces the cost of the fabrication. Furthermore, by removing the conventional backside etch window, the process enables solid, compact, and robust chip designs that significantly eases handling and packaging. To achieve 2-D imaging in dual-axis confocal microscopy, our scanner is gimbaled, but the outer frame of the gimbal is removed in order to minimize the size of the scanner chip. In static operation, the scanner has optical deflection angles of ~±5.5° at 190V and ±3.8° at 100V for the outer and inner axes, respectively. At the torsional resonances, the optical deflection increases to ±11.8° at 1.18kHz for the outer axis and ± 8.8° at 2.76kHz for the inner axis, when the mirror is driven by (62 + 37sinωt)V and (68 + 37sinωt)V, respectively.
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In this paper, we present a novel 2-D microelectromechanical systems (MEMS) scanner that enables dual-axes confocal microscopy. Dual-axes confocal microscopy provides high resolution and long working distance, while also being well suited for miniaturization and integration into endoscopes for in vivo imaging. The gimbaled MEMS scanner is fabricated on a double silicon-on-insulator (SOI) wafer (a silicon wafer bonded on a SOI wafer) and is actuated by self-aligned vertical electrostatic combdrives. Maximum optical deflections of plusmn4.8deg and plusmn5.5deg are achieved in static mode for the outer and inner axes, respectively. Torsional resonant frequencies are at 500 Hz and 2.9 kHz for the outer and inner axes, respectively. The imaging capability of the MEMS scanner is successfully demonstrated in a breadboard setup. Reflectance images with a field of view of are achieved at 8 frames/s. The transverse resolutions are 3.94 mum and 6.68 mum for the horizontal and vertical dimensions, respectively.
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Full-text available
In this paper, we present the design, fabrication, and measurements of a two-dimensional (2-D) optical scanner with electrostatic angular vertical comb (AVC) actuators. The scanner is realized by combining a foundry-based surface-micromachining process (Multi-User MEMS Processes-MUMPs) with a three-mask deep-reactive ion-etching (DRIE) postfabrication process. The surface-micromachining provides versatile mechanical design and electrical interconnect while the bulk micromachining offers high-aspect ratio structures leading to flat mirrors and high-force, large-displacement actuators. The scanner achieves dc mechanical scanning ranges of ±6.2° (at 55 Vdc) and ±4.1° (at 50 Vdc) for the inner and outer gimbals, respectively. The resonant frequencies are 315 and 144 Hz for the inner and the outer axes, respectively. The 1-mm-diameter mirror has a radius of curvature of over 50 cm. [1454].