Presented here is the optical characterization and 2D scanning capabilities of an SU-8 based waveguide scanner. Transducing a resonant microcantilever in both the vertical and horizontal direction provides a raster motion useful for imaging when in combination with light source and detector. An application of this design can be in the area of endoscopy where noninvasive instrumentation is desired. MEMS fabricated polymeric devices will allow reduction of the overall size of the system while maintaining the resolution and field-of-view (FOV) of current endoscopes. Our design provides the initial phases for the realization of this system. A waveguide scanner has been fabricated with a 50x100mm cross section and beam length of 2mm. Mode coupling from input to output of the structural design has been determined to be 71.4%. Total power output measured experimentally to be 20%. Preliminary tests have shown 2D imaging with digital processed reconstruction.
A flexible high-resolution sensor capable of measuring the distribution of both shear and pressure at the plantar interface are needed to study the actual distribution of this force during daily activities, and the role that shear plays in causing plantar ulceration. We have previously developed a novel means of transducing plantar shear and pressure stress via a new microfabricated optical system. However, a force image algorithm is needed to handle the complexity of construction of two-dimensional planar pressure and shear images. Here we have developed a force image algorithm for a micromachined optical bend loss sensor. A neural network is introduced to help identify different load shapes. According to the experimental result, we can conclude that once the neural network has been well trained, it can correctly identify the loading shape. With the neural network, our micromachined optical bend loss Sensor is able to construction the two-dimensional planar force images.
The use of SU-8 in recent years has spawned new developments in MEMS technologies due to its low cost and well characterized mechanical and optical properties. SU-8 is a high contrast, negative tone, chemically amplified, epoxy based photoresist. Considered the poor man's LIGA, the resist is recognized for its high aspect ratio (~15:1), great for vertical sidewalls. Designs of ink jets, micro fluidic devices, and optical devices are a few examples that the material has been used for. Written here is the fabrication and test analysis of a MEMS optical scanner. The scanner is a new stage development to the previous microfabricated Si/SiO2 cantilever beam which was fabricated for the purpose of endoscope examination. The current design has improved performance and “ease of use” with the implementation of SU-8 as the foundation to the optical waveguide or scanner. With this new device, larger thicknesses were achieved as compared to the previous method. Fabrication of the SU-8 waveguide was measured to be ~85μm as compared to the silixon oxide method of ~3μm. An overall larger device makes coupling a fiber into the waveguide much easier and increases the amount of light coupled into the beam. The optical scanner consists of a cantilever beam with a U-shaped groove for optical coupling. In this paper, we will discuss the image scanning capabilities of the device.
Lower limb complications associated with diabetes include the development of plantar ulcers that can lead to infection and subsequent amputation. While it is known from force plate analyses that there are medial/lateral and anterior/posterior shear components of the ground reaction force, there is little known about the actual distribution of this force during daily activities, nor about the role that shear plays in causing plantar ulceration. Furthermore, one critical reason why these data have not been obtained previously is the lack of a validated, widely used, commercially available shear sensor, in part because of the various technical issues associated with shear measurement. Here we have developed novel means of tranducing plantar shear and pressure stress via a new microfabricated optical system. The pressure/shear sensor consists of an array of optical waveguides lying in perpendicular rows and columns separated by elastomeric pads. A map of pressure and shear stress is constructed based on observed macro bending through the intensity attenuation from the physical deformation of two adjacent perpendicular optical waveguides. The uniqueness of the sensor is in its batch fabrication process, which involves injection molding and embossing techniques with Polydimethylsiloxane (PDMS) as the optical medium. Here we present the preliminary results of the prototype. The sensor has been shown to have low noise and responds linearly to applied loads. The smallest detectable force on each sensor element based on the current setup is ~0.1 N. The smallest area we have resolved in our mesh sensor is currently 950x950μm2
Flexible medical endoscopes currently used in medicine have many problems and a fundamental tradeoffs. Either resolution or field of view is sacrificed when the scope diameter is less than 3mm, since the minimum pixel size is usually at least 4 microns in a pixel-array such as a camera or fiber bundle. Previous work has shown the design of a micromachined cantilever beam able to realize a 100μm wide, one dimension scanning pattern. First mode resonances of the cantilever scanner are found between 16-52 kHz with response amplitudes ranging from 62.5 to 420 μm. Since cantilever waveguides with resonant frequencies above 20 kHz are potentially suitable for video rate scanning, these devices may be used for image acquisition and display. Described in this work is an alternative method of design for a micro-optical scanning endoscope. The endoscope consists of an optical waveguide microfabricated using SU-8 photoresist. SU-8 is a high contrast, negative tone, chemically amplified, epoxy based photoresist chosen for its high aspect ratio (~15:1) for imaging near vertical sidewalls. With the use of SU-8, we were able to fabricate a much larger waveguide (~85 μm) as compared to the previous silicon oxide method (~3 μm) An overall larger device makes coupling a fiber into the waveguide much easier and increases the amount of light coupled into the cantilever beams. The neagactively toned epoxy resin based SU-8 also increases the device durability and simplifies the fabrication process.