Nanosatellites, in particular the sub-class of CubeSATs, will provide an ability to place multiple small satellites in space
more efficiently than larger satellites, with the eventual expectation that they will compete against some of the roles
played by traditional large satellites that are expensive to launch. In order to do this, it is necessary to decrease the
weight and volume without decreasing the capabilities. At the same time, it is desirable to create systems extremely
rapidly, less than a week from concept to orbit. The Air Force has been working on a concept termed "CubeFlow"
which will be a web-based design flow for rapidly constructible CubeSAT systems. In CubeFlow, distributed suppliers
create offerings (modules, software functions, for satellite bus and payloads) meeting standard size and interface
specifications, which are registered as a living catalog to a design community within the web-based CubeFlow
environment. The idea of allowing any interested parties to make circuits and sensors that simply and compatibly
connect to a modular satellite carrier is going to change how satellites are developed and launched, promoting creative
exploitation and reduced development time and costs. We extend the power of the CubeFlow framework by a concept
we call "print-and-play." "Print-and-play" enriches the CubeFlow concept dramatically. Whereas the CubeFlow system
is oriented to the brokering of pre-created offerings from a "plug-and-play" vendor community, the idea of "print-andplay"
allows similar offerings to be created "from scratch," using web-based plug-ins to capture design requirements,
which are communicated to rapid prototyping tools.
Laser micromachining combined with digital printing allows rapid prototyping of complex bioreactors with reduced fabrication times compared to multi-mask photolithography. Microfluidic bioreactors with integrated optical waveguides for diagnostics have been fabricated via ultrashort pulse laser micromachining and digital printing. The microfluidic channels are directly laser machined into poly(dimethylsiloxane) (PDMS) silicone elastomer. Multimode optical waveguides are formed by coating the PDMS with alternating refractive index polymer layers and laser machining to define the waveguide geometry. Tapered alignment grooves are also laser machined to aid in coupling optical fibers to the waveguides. Three-dimensional (3-D) bio-scaffold matrices comprising liquid solutions that can be selectively and rapidly gelled are digitally printed inside the bioreactors and filled with nutrient rich media and cells. This paper will describe the maskless fabrication of complex 3-D bioreactors and discuss their performance characteristics.
Novel devices can be relatively simple in theory and modeling, but difficult and many times unfeasible to fabricate in a traditional cleanroom environment. We have developed a CAD/CAM tool capable of integrating multiple materials in the electronic, photonic, and biological regimes for applications in both MEMS and BioMEMS devices. Some materials are known and more fully characterized, such as thick film resistors or conductors, while other materials such as biodegradable scaffolding are new but showing promise to realize heterogenous tissue engineered constructs and drug delivery devices. The tool does not discriminate, but rather places these materials in specified locations with precision volumetric control, gently, conformally, and in 3-D. This paper will describe the enabling aspect of true 3-D maskless fabrication as well as describe multiple device structures and demonstrations.
Using a Ti:Sapphire laser operating at 800nm and a repetition rate of 1 kHz, we investigated the damage induced to fresh cadaveric porcine liver after laser irradiation for pulse widths of 120-fs, 8ps, and 7-ns. The laser was held constant at a focal spot diameter of 100μm yielding a maximum fluence of 9J/cm<sup>2</sup>. Then, using polarization optics, the energy per pulse was controlled to well below ablation threshold fluences. The tissue samples were translated under the laser via 0.1μm resolution encoded X-Y-Z motorized stages. After irradiation and fixation, we evaluated the tissues using brightfield light microscopy of Hematoxylin and Eosin stained 4 μm thick cross sections, scanning electron microscopy, and transmission electron microscopy. The tissue samples were examined for both removal rates of material, thermal damage to surrounding tissue, and cell disruption for equivalent fluence levels across the temporal range. We found an increase in removal rate along with a decrease in thermal damage as the pulse widths approached the femtosecond regime for a constant fluence. With femtosecond pulses, ablation still occurred below fluences of 2J/cm<sup>2</sup>. However, for nanosecond pulses, ablation no longer occurred, showing a decrease in ablation threshold as the pulse width decreases. Because of the reduced thermal effects compared to nanosecond pulses, ultrafast lasers may offer a solution to more precise tissue removal with less damage to surrounding cells.
Tissue ablation with pulses in the femtosecond regime is generally more efficient and causes less collateral and thermal damage to the surrounding tissue compared to ablation with longer pulsewidths. A compact, flexible fiber delivery system that could transmit these pulses would be advantageous over free-space beam delivery, since it would allow ultrashort pulse tissue ablation <i>in vivo</i>. However, the extremely high intensities associated with ultrashort pulses have deleterious effects in conventional silica fibers such as nonlinearities and fiber damage. Hollow silica waveguides with a silver inner coating essentially guide the pulses in air, thereby avoiding many of these problems. The transmission characteristics of four hollow waveguides with bore diameters of 300, 500, 750 and 1000μm and lengths up to 1m were tested using pulses from a femtosecond regime Ti:Sapphire laser operating with input pulses <150fs duration and energy up to 700 microjoules at a repetition rate of 1kHz. Coupling was primarily to the HE<sub>11</sub> mode and straight and bending losses were measured. Beam profiles were also taken at the output of straight and bent waveguides. Autocorrelation measurements show minimal pulse broadening for straight waveguides and increasing pulsewidth with waveguide bend. Diffractive micro-optics were used to focus the output and ablation of fresh cadaveric porcine liver and heart tissues was accomplished using an x-y-z translational stage moving at 1 mm/second. Targeted tissues were then processed for light and electron microscopic examination. Light and scanning electron microscopy demonstrated near a-thermal ablation with depth correlating to energy application.
Multimode optical waveguides have been fabricated by dispensing photopolymers onto various substrates using direct-write technologies. Fine-tuning is achieved by micromachining the waveguides using a femtosecond-regime pulsed laser. Propagation losses are determined using the cutback method. A 2 × 2 coupler and a 1 × 8 splitter are demonstrated.
Surface modification of aluminum alloy 2024-T3 using femtosecond pulsed excimer laser irradiation was studied at 248 nm. The images of the scanning electron microscopy (SEM) were characterized as a function of incident laser fluence. Results indicated that the surface features, ranging from nano- to microdimension, can be developed through variation in laser fluence intensities and pulse counts. Two ablation regimes in the logarithmic fluence dependence of the ablated depth for the 500 fs-pulse irradiation were observed. The theoretical analysis for ablation processes is in a good agreement with the experimental results.
We report recent results from our work on the fabrication of neodymium waveguide lasers. Several neodymium doped glasses. APG-1, LG-680, BK 7 and S 3 made by Schott Glass Technologies, Inc. were studied as candidates for use as waveguide lasers. It was found that S 3, a standard ophthalmic glass, had the best ion-exchange properties of any of the glasses studied. A waveguide laser was successfully made using the neodymium doped S 3 glass.
Polarization dependent integrated optical devices are becoming increasingly important in order to control polarization for coherent optical detection schemes, gyros, bidirectional communications using optical circulators, electro-optical switching and electro-optical phase modulation. Typically, integrated optical components are made by titanium diffusion into LiNbO<SUB>3</SUB>, ion-exchange or electric field assisted ion diffusion in glasses. The diffused ion concentrations determine the waveguide properties. Theloped to understand the physical limitations of these devices, and the necessary electrical characteristics that the KD<SUP>*</SUP>P modulators must have for use in the MSFC polarimeter. imaging systems. A near infra-red imaging polarimeter is used to measure the cubes. measurement using a known Stokes source. We discuss our work implementing computer-aided polarimetry using the Mueller calculus and applius to design waveguide structures for polarization integrated optical devices.