Dr. Woo Ho Lee Profile

Dr. Woo Ho Lee

Research Scientist at Univ of Texas at Arlington

SPIE Involvement:

Author

Proceedings Article | 13 May 2016 Paper

Piezoresistive pressure sensor array for robotic skin

Fahad Mirza, Ritvij Sahasrabuddhe, Joshua Baptist, Woo H. Lee, Dan Popa, Muthu Wijesundara

Proceedings Volume 9859, 98590K (2016) https://doi.org/10.1117/12.2225411

KEYWORDS: Sensors, Robotics, Skin, Robots, Printing, Environmental sensing, Skin, Environmental sensing, Signal to noise ratio, Humidity, Manufacturing, Silicon

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Proceedings Article | 13 May 2016 Paper

Package analysis of 3D-printed piezoresistive strain gauge sensors

Ritvij Sahasrabuddhe, Sumit Kumar Das, Joshua Baptist, Woo H. Lee, Dan Popa

Proceedings Volume 9859, 985905 (2016) https://doi.org/10.1117/12.2224352

KEYWORDS: Sensors, Skin, Finite element methods, 3D modeling, Polymers, Silicon, Resistance, Polymeric sensors, Data modeling, Gold

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Proceedings Article | 2 June 2015 Paper

EHD printing of PEDOT: PSS inks for fabricating pressure and strain sensor arrays on flexible substrates

Muthu B. Wijesundara, Joshua Baptist, Woo Ho Lee, Dan Popa, Caleb Nothnagle, Joe Sanford

Proceedings Volume 9494, 949403 (2015) https://doi.org/10.1117/12.2177415

KEYWORDS: Sensors, Printing, Resistance, Electrodes, Skin, Robotics, Inkjet technology, Teeth, Additive manufacturing, Fabrication

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Proceedings Article | 5 June 2014 Paper

Tactile MEMS-based sensor for delicate microsurgery

Young Soo Park, Wooho Lee, Nachappa Gopalsami, Mohan Gundeti

Proceedings Volume 9116, 911603 (2014) https://doi.org/10.1117/12.2058250

KEYWORDS: Sensors, Tissues, Surgery, Haptic technology, Robotic surgery, Microelectromechanical systems, Spatial resolution, Photoresist materials, Resistors, Resistance

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Proceedings Article | 4 June 2014 Paper

EHD as sensor fabrication technology for robotic skins

Jeongsik Shin, Woo Ho Lee, Caleb Nothnagle, Muthu Wijesundara

Proceedings Volume 9116, 91160F (2014) https://doi.org/10.1117/12.2053429

KEYWORDS: Printing, Sensors, Skin, Robotics, Zinc oxide, Inkjet technology, Gold, Silicon, Lithography, Metals

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Proceedings Article | 4 June 2014 Paper

Experimental testbed for robot skin characterization and interaction control

Ahsan Habib, Kyle Shook, Woo Ho Lee, Dan Popa

Proceedings Volume 9116, 911606 (2014) https://doi.org/10.1117/12.2049956

KEYWORDS: Skin, Sensors, Silicon, Actuators, Computer programming, Calibration, Motion measurement, Statistical modeling, Control systems, Servomechanisms

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Proceedings Article | 24 May 2011 Paper

Microrobotics surveillance: discrete and continuous starbot

W. H. Lee, Harry Stephanou, M. Mayyas

Proceedings Volume 8045, 804510 (2011) https://doi.org/10.1117/12.884172

KEYWORDS: Robots, Manufacturing, Microsystems, Composites, Prototyping, Robotics, Actuators, Surveillance, Polymers, Sensors

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Proceedings Article | 28 April 2010 Paper

Sensitivity analysis of an assembled Fourier transform microspectrometer

Woo Ho Lee, Jeongsik Sin, Harry Stephanou

Proceedings Volume 7680, 76800T (2010) https://doi.org/10.1117/12.850800

KEYWORDS: Sensors, Mirrors, Fourier transforms, Optical components, Beam splitters, Kinematics, Error analysis, Tolerancing, Signal detection, Silicon

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Proceedings Article | 12 May 2009 Paper

Design and fabrication of microflap actuators for steering of micro air vehicles

Woo Ho Lee, Dan Popa, George Zimbru

Proceedings Volume 7318, 73180R (2009) https://doi.org/10.1117/12.819533

KEYWORDS: Magnetism, Actuators, Microelectromechanical systems, Semiconducting wafers, Micro unmanned aerial vehicles, Silicon, Deep reactive ion etching, Electromagnetism, Manufacturing, Microactuators

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Proceedings Article | 8 January 2007 Paper

An active locking mechanism for assembling 3D micro structures

Woo Ho Lee, J. Chiao, Dan Popa, Panos Shiakolas, Mohammad Mayyas, Harry Stephanou, Ping Zhang

Proceedings Volume 6414, 641425 (2007) https://doi.org/10.1117/12.696181

KEYWORDS: Actuators, Deep reactive ion etching, Semiconducting wafers, Silicon, Photoresist materials, Microsystems, Materials processing, Metals, Photomasks, Scanning electron microscopy

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Microassembly is an enabling technology to build 3D microsystems consisting of microparts made of different materials and processes. Multiple microparts can be connected together to construct complicated in-plane and out-of-plane microsystems by using compliant mechanical structures such as micro hinges and snap fasteners. This paper presents design, fabrication, and assembly of an active locking mechanism that provides mechanical and electrical interconnections between mating microparts. The active locking mechanism is composed of thermally actuated Chevron beams and sockets. Assembly by means of an active locking mechanism offers more flexibility in designing microgrippers as it reduces or minimizes mating force, which is one of the main reasons causing fractures in a microgripper during microassembly operation. Microgrippers, microparts, and active locking mechanisms were fabricated on a silicon substrate using the deep reactive ion etching (DRIE) processes with 100-um thick silicon on insulator (SOI) wafers. A precision robotic assembly platform with a dual microscope vision system was used to automate the manipulation and assembly processes of microparts. The assembly sequence includes (1) tether breaking and picking up of a micropart by using an electrothermally actuated microgripper, (2) opening of a socket area for zero-force insertion, (3) a series of translation and rotation of a mating micropart to align it onto the socket, (4) insertion of a micropart into the socket, and (5) deactivation and releasing of locking fingers. As a result, the micropart was held vertically to the substrate and locked by the compliance of Chevron beams. Microparts were successfully assembled using the active locking mechanism and the measured normal angle was 89.2°. This active locking mechanism provides mechanical and electrical interconnections, and it can potentially be used to implement a reconfigurable microrobot that requires complex assembly of multiple links and joints.

Proceedings Article | 23 January 2006 Paper

Assembled Fourier transform micro-spectrometer

Woo Ho Lee, Jeongsik Sin, Harry Stephanou, Dan Popa

Proceedings Volume 6109, 610904 (2006) https://doi.org/10.1117/12.643872

KEYWORDS: Mirrors, Fourier transforms, Beam splitters, Actuators, Silicon, Spectroscopy, Reactive ion etching, Optical benches, Michelson interferometers, Sensors

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Microassembly process plays a key role in building 3-dimensional heterogeneous microsystems. This paper presents a miniaturized Fourier transform spectrometer (FTS) implemented by combining silicon micromachining and microassembly techniques. The FTS is based on a Michelson interferometer where a scanning mirror mechanism creates an interferogram, and the recorded interferogram is converted to a spectrum by Fourier transform. The miniaturized Michelson interferometer is integrated on a microoptical bench, which is fabricated using Deep RIE (Reactive Ion Etching) process on a SOI (Silicon On Insulator) wafer. Key components of the FTS optical bench are a linear translation stage, mechanical assembly sockets, a beam splitter, and assembled mirrors. An electrothermal actuator with stroke amplification mechanisms provides the amplified scanning motion of a scanning mirror. The sockets are female mechanical flexure structures that allow a precise snap-fit assembly with micromachined silicon mirrors. The dimension of the FTS optical bench is 1cm², and its embedded thermal actuator has a couple of V-beam structures whose beam length is 1mm. The mirrors are Deep RIE micromachined structures with reflection area 500x450μm² and 750μm long flexure structures for pick & place assembly. The flexure structure allows large deflection so that a microgripper can pick up the mirror by inserting the gripper tip into the structure, and snap-fit assembles it into the mechanical socket of the bench. The linear translation stage generates up to 30μm scanning stroke at 22V input, which corresponds to a spectral resolution of 10nm at 775nm wavelength. While this microassembly method is designed to self-align the mirror in the socket, the mirror slightly tilts after assembly due to the slope of side wall of DRIE processed structures. The measured tilting angles of assembled mirrors range from -2.5° to 0.8° from several assembly trials. The tilting angle combined with beam divergence can cause the loss of power and resolution, spectrum shift and phase error. A He-Ne laser was used as a light source to create interferogram with the assembled microspectrometer. Formation of fringe patterns was successfully conducted with a prototype. Mirrors with a large tilting misalignment resulted in stripe pattern fringes, whereas an improved alignment generated circular pattern fringes. A detector was used to measure light power with respect to input voltage, and the displacement of a scanning mirror was measured and curve-fitted. The relationship between light power changes versus the displacement of a scanning mirror represents interferogram. Spectrum profiles showed a peak around 632nm with FWHM (Full Width Half Magnitude) 25nm approximately. While further research is on going to improve spectrum quality and microassembly technique for the integration of various components with heterogeneous materials and shapes, this approach is expected to facilitate the design and manufacturing of MOEMS from the constraints of micromachining processes.

Showing 5 of 11 publications

Conference Committee Involvement (1)

Micro- and Nanotechnology: Materials, Processes, Packaging, and Systems III

11 December 2006 | Adelaide, Australia

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