Prof. Edwin En-Te Hwu Profile

Prof. Edwin En-Te Hwu

Associate Professor at Technical Univ of Denmark

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Publications (4)

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Proceedings Article | 5 March 2021 Poster + Presentation + Paper

Submicron scale stereolithography using HD-DVD optical pickup unit

Tien-Jen Chang, Lukas Vaut, Martin Voss, Oleksii Ilchenko, Line Hagner Nielsen, Anja Boisen, En-Te Hwu

Proceedings Volume 11677, 1167718 (2021) https://doi.org/10.1117/12.2575936

KEYWORDS: 3D printing

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It is challenging for stereolithography systems to print submicron features without two-photon lasers. For the first time, we implement an HD-DVD optical pickup unit (OPU) for building a customized stereolithography 3D printer. The OPU equips a 405 nm single-photon laser and an objective lens with a numerical aperture of 0.65. This has a focal laser spot diameter of 430 nm (1/e²) and can thereby, achieve submicron scale features photopolymerization. Moreover, the OPU embeds astigmatic optical path and voice coil motor which can be used for closed-loop printing alignment and this increases printing stability significantly. The OPU 3D printing system integrates an XYZ linear stage, providing nanoscale positioning resolution and macroscale printing area (c.a. 50 X 50 X 25 mm). A commercial photo-resin is utilized for the assessment of the system performance. The OPU printer crosslinks structures ranging from tens of microns down to submicron scale by tuning the printing parameters (laser intensity, printing speed, and photo-resin thickness). After optimization of the system, the OPU printer achieved the highest printing resolution of 210 nm which is beyond conventional stereolithography systems. Furthermore, several microstructures have been printed for verifying multiple layer printing performance. In conclusion, the mass-produced, low-cost and compact size OPU can not only dramatically simplify the stereolithography 3D printer design, but also achieve submicron printing performance.

Proceedings Article | 5 March 2021 Presentation + Paper

Hacking blu-ray drives for high-throughput 3D printing

Edwin En-Te Hwu, Martin Voss, Tien-Jen Chang, Hsien-Shun Liao, Anja Boisen

Proceedings Volume 11677, 116770A (2021) https://doi.org/10.1117/12.2576491

KEYWORDS: 3D printing, Printing, Photopolymers, Spindles, Solids, Signal detection, Scanning electron microscopy, Raster graphics, Multilayers

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Conventional microscale 3D printing techniques mostly rely on the raster scanning method, which needs constant changing of printer head/light beam/substrate directions to print a solid structure. Therefore, throughput is a longstanding bottleneck and it is more challenging to print microfeatures in large areas. This study demonstrates the possibility of 3D printing microfeatures on a fast-spinning disc. A Blu-ray drives based high-throughput 3D printer (BRIGHT^3D) is developed to demonstrate the spin printing on disc concept and evaluate the highest linear printing speed. The BRIGHT^3D integrates two Blu-ray drives that are synchronized by a customized controller. The printing substrate is a standard Blu-ray RW disc spun by a spindle motor. Both drives utilize the same optical pick-up unit (OPU), which equips a voice coil motor (VCM) for the disc wobbling compensation. The bottom OPU detects the disc wobbling and feeds the VCM control signal back to top OPU for maintaining laser (405 nm, 658 microwatts) focused on the spinning substrate disc. The BRIGHT^3D can directly spin-coat (up to 6,440 rpm) commercial photopolymers with a controllable thickness on top of the substrate disc. The top OPU laser was switched with a frequency of 1~500 kHz (duty cycle: 80 %) for the preliminary spinning 3D printing evaluation. Microfeatures can be cured by the BRIGHT^3D while the disc is spinning at a speed of 265 rpm, which has a linear speed from inner diameter, 20 mm, to the outer diameter, 58.5 mm, of 0.55~1.63 meters per second. After removing the photopolymer residues by 75% ethanol, various microscale features on the disc can be seen and measured by scanning electron microscopy. Microscale lines (height/width: 1.43/8.25 microns) and dots (length: 5.97 microns) were successfully printed on the disc. The BRIGHT^3D is aiming for multiple layer printing on the disc to realize sophisticated features of high-throughput 3D printing in the near future.

Proceedings Article | 5 May 2010 Paper

High-throughput readout system for cantilever-based sensing of explosive compounds

F. Bosco, E.-T. Hwu, A. Boisen

Proceedings Volume 7679, 767925 (2010) https://doi.org/10.1117/12.850008

KEYWORDS: Explosives, Sensing systems, Sensors, Photodetectors, Gold, Silicon, Molecules, Polymers, Head, Calibration

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Cantilever based sensors are promising miniaturized sensing tools for bio-chemical applications [1]. These micromechanical sensors can be employed to sense very small amounts of dangerous substances like explosive molecules, biological threats and hazardous compounds, both in air or liquid environment. In our project we focus on the development of a new readout system for employing of this sensing technique for detection of explosives like TNT, RDX and PETN, under the framework of the Xsense project. At present available optical equipments for cantilever sensing are typically big and bulky, making the in situ employment of this technology still very hard. Here we present a novel approach to measure the absorption of masses on the cantilever surfaces by using a light, compact, portable and high throughput optical device. Our setup is able to measure real time both the deflection of the beams and their vibrational frequencies, employing the same laser source and the same photodetector. The optical readout of cantilever-based sensors was re-designed and developed combining the technology of commercial DVD-ROM readers [2] with polymer based holding substrates structured with UV-lithography or imprint technology. Cantilever chips are clamped on a predefined holding substrate structured in SU-8 or in Cyclic Olefin Copolymer (COC), while the DVD-ROM reader is placed 1 mm below the substrate. The laser beam is collimated and focused on cantilevers with a 0.75 μm spot diameter and the reflected light is then recorded using an astigmatism-based 4-quadrant photodetector. The integration of the DVD-ROM reader with the on-substrate holding approach leads to a high throughput flexible platform with easy auto-alignment and replacement of the cantilevers chips. With this new on-substrate approach tens of chips can be placed on the Polymer holder and be read sequentially in a very light and compact device.

Proceedings Article | 25 October 2004 Paper

SMM actuator for nanoscale positioning

E. Hu, Kuang-Yuh Huang, Ing-Shouh Hwang

Proceedings Volume 5602, (2004) https://doi.org/10.1117/12.570786

KEYWORDS: Actuators, Scanning probe microscopy, Sensors, Electroluminescence, Interferometers, Motion models, Mechanical engineering, Nanotechnology, Nanomanipulation, Scanning tunneling microscopy

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This paper presents a new design of a Shear Motion Mode (SMM) actuator for ultra-high precision positioning in nanotechnological applications. In the SMM Actuator, a V-shape stage is driven by four parallel polarized piezoelectric plates with shear displacement. Based on its simple mechanism, the SMM actuator can be built very compactly. For fast and precision positioning tasks, we develop three different driving modes to control the SMM actuator. For large stroke, the inertial and frictional driving modes are applied for fast and precision positioning, respectively. The scanning mode enables the adjustment of the scanning distance in highest resolution. Positioning function of the developed SMM actuator may also be brought into applications in the low temperature and Ultra High Vacuum (UHV) environment. These three driving modes are experimentally tested to measure their dynamic performance. The stroke of the SMM actuator is 5mm. By applying the frictional driving mode, the SMM actuator can achieve a positioning resolution of 3nm with a pay load of 500g.

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