The emergence of vertical cavity surface emitting laser (VCSEL) and photo diode (PD) arrays has given scope for the development of many applications such as high speed data communication. Further increase in performance can be obtained by the inclusion of micro-mirrors and microlens in the optical path between these components. However, the lack of efficient assembly and alignment techniques has become bottlenecks for new products. In this paper, we present development of optical sub-assembly and metallic MEMS structures that enable in the massively parallel assembly and alignment of these components to form a single miniature package. VCSEL wafer was processed to have polymer pedestal and polymeric lens on top of it. Such optical sub assembly greatly increases coupling efficiency between the VCSEL and optical fibers. Multiple numbers of suspended MEMS serpentine springs made out of electroplated nickel have been fabricated on ceramic substrates. These springs serve for clamping and alignment of multiple numbers of optoelectronic components. They are designed to be self-aligning with alignment accuracies of less than 3 micron after final assembly. Electrical connection between the bond pads of VCSEL's and PD's to the electrical leads on the substrate has been demonstrated by molten solder inkjet printing into precisely designed MEMS mold structures. This novel massively parallel assembly process is substrate independent and relatively simple process. This technique will provide reliable assembly of optoelectronic components and miniature optical systems in low cost mass production manner.
Precision micro-dispensing based upon ink jet technology has been used in medical diagnostics since the early nineties, and now is moving into a wide range of applications. Ink-jet printing technology can reproducibly dispense micro-droplets of fluid with diameters of 15 to 100 μm (2pl to 5nl) at rates of 0 - 25,000 per second from a single drop-on-demand printhead. The deposition is non-contact, data-driven and can dispense a wide range of fluids. It is a key enabling technology in the development of Bio-MEMS devices, Sensors, Micro-fluidic devices and Micro-optical systems. In this paper, we will discuss the use of this technology for real time calibration and testing of chemical sensors. The technology is based upon test systems developed for olfaction testing which are capable of precisely dispensing chemical aromas in concentration that vary over 6 orders of magnitude. The droplets of each chemical are thermally converted into a vapor that is fed directly into the sensor under test.
Precision micro-dispensing based upon ink jet technology has been used in medical diagnostics since the early nineties, and now is moving into a wide range of applications. Ink-jet printing technology can reproducibly dispense spheres of fluid with diameters of 15 to 100 μm (2pl to 5nl) at rates of 0 - 25,000 per second from a single drop-on-demand printhead. The deposition is non-contact, data-driven and can dispense a wide range of fluids. It is a key enabling technology in the development of Bio-MEMS devices, Sensors, Micro-fluidic devices and Micro-optical systems. In this paper, we will discuss the use of this technology for miniature chemical and bio-molecular sensors and will review in detail specific applications.
Direct write microprinting technologies are now being developed and used across a wide spectrum of optoelectronic applications, because they provide opportunities for manufacturing a series of components in micrometer scales and in large array size with reduced cost. Micro-optic structures have been printed not only as stand-alone components, but also directly onto other active and passive components, such as VCSEL, photodiode, optical fiber, etc., to form high performance assemblies. These assemblies can be further integrated with electronic circuits via solder ball printing to construct miniature and high sensitivity sensing devices, such as photodiode array detector, fluorescence probe, etc. By implementing MEMS technologies, micro-clampers have also been developed for the alignment and packaging of miniature, multi-channel sensing devices.
Ink-jet printing technologies are now being developed and used across a wide spectrum of optoelectronic and microelectronic manufacturing applications, because they provide opportunities both for significant cost reductions in existing components and for new component and device configurations. Examples of cost reductions in existing component configurations include printing of optical epoxies to fabricate precision microlens arrays for micro-mirror-based MEMS optical switches and fluxless printing of solder bumps for flip-chip BGA, μBGA and CSP (chin-scale package) manufacture. The most widely recognized, relatively new application of ink-jet printing has arisen in the manufacturing of PLED (Polymer-LED) displays. Potential uses of these technologies for creating new device and package configurations that provide both higher performance and lower cost include microlens printing directly onto VCSELs or the tips of optical fibers for increasing the efficiency of coupling and solder ball printing for making right-angle electrical connections, in order to enable further miniaturization of optoelectronic packages. Example ofnew device configurations which may be fabricated using these capabilities include chip-level optical switches, transceivers, transmitters and receivers.
A significant advance in technical capability has recently been achieved in the fabrication of refractive microlens arrays by microjet printing. This advance enables control of lens diameter and center-to-center distances to accuracies on the order of +/- 1 micrometers , and of focal length variations within an array to less than the +/- 1%. Such accuracies are especially important for microlens arrays used for MOEMs device interconnects to optical fibers because of the relatively long free space optical path lengths required for such applications. The new process also enables the printing of microlenses of a given diameter with aspect ratios and focal lengths varying over a wide range (e.g., f/1-f/5). The profile of plano-convex microlenses printed by this method have exhibited less than a quarter wavelength of deviation from spherical surface. The thermal durability of the optical epoxies used for microlens printing enables both cycling temperature up to 200 degree(s)C and continuous exposure to thousands of hours at 85 degree(s)C, without affecting microlens performance. The microjet printing of lensed fibers provides another solution for fiber beam shaping and collimation with low production cost.
Micro-optoelectronic mechanical systems (MOEMS) typically rely on free-space optical interconnects for fiber array in/out connections. The fiber output collimating and input focusing functions may be performed by using either individual gradient-index-of-refraction (GRIN) microlens rods or, more typically, arrays of microlenses formed on a glass substrate, to which the fibers are butte-coupled. We present methods for fabricating, with micron precision, various configurations of micro-optics for fiber collimation using low-cost, ink-jet printing technology. These configurations range from micro-deposition of droplets of optical epoxy into the tips of fibers, positioned in either individual collets or fiber ribbon connector ferrules, to the printing of arrays of collimating/focusing microlenses onto glass substrates. In the latter case the flexibility of the data-driven printing process enables unique capabilities, such as the variation of microlens geometries within an array, in order, for example, to compensate for the varying distances between the input fibers and the individual micro-mirrors within an array of a MOEMS device. The processes and optical modeling approaches used for fabricating such fiber collimation structures utilizing ink- jet printing technology will be discussed in detail, along with process control issues and optical performance data.
KEYWORDS: Printing, Microelectromechanical systems, Control systems, Polymers, Packaging, Manufacturing, Adhesives, Microlens, Microfluidics, Chemical elements
Ink-jet printing technology is, in many ways, ideally suited for addressing a number of these MEMS device packaging challenges. The general advantages of this form of microdispensing derive from the incorporation of data-driven, non-contact processes which enable precise, picoliter-level volumes of material to be deposited with high accuracy and speed at target sites, even on non-planar surfaces. Being data-driven, microjet printing is a highly flexible and automated process which may readily be incorporated into manufacturing lines. It does not require application-specific tooling such as photomasks or screens, and, as an additive process with no chemical waste, it is environmentally friendly. In short, the advantages obtainable with incorporation of micro-jet printing technology in many fabrication applications range from increased process capability, integration and automation to reduced manufacturing costs.
The microjet printing method is being used to fabricate microlenses for free-space optical interconnects in telecommunication devices. This low-cost, data-driven process, based on `drop-on-demand' inkjet technology, involves the dispensing and placing of precisely sized micro-droplets of 100%-solids, UV-curing optical epoxy pre- polymers at elevated temperatures onto optical substrates and components. The method offers significant cost advantages in the fabrication of components such as precision lens arrays and fiber ribbon collimators for use in certain configurations of DWDM multiplexing- demultiplexing devices and optical switches.
The microjet printing method is being used to fabricate microlens arrays for use in massively parallel, VCSEL-based datacom switches and to deposit lenslets of various configurations onto the tips of single-mode telecom fibers. Applications in the latter case include collimation of the output beams for free space optical interconnection and increasing the fiber numerical aperture for collection of light from edge-emitting diode lasers. Additional applications of this technology include point of arrays of active sensor elements onto the tips of imaging fiber bundles and fabrication of microlenses with axial index of refraction gradients to reduce focal spot size, utilizing multiple print heads with differing fluids. This low-cost, data-driven process, based on 'drop-on-demand' inkjet technology, involves the dispensing the placing of precisely sized microdroplets of optical material onto optical substrates. The micro-optical elements are printed with 100 percent solid, UV-curing optical epoxies, utilizing printing devices that can dispense picoliter-volume droplets at temperatures up to 300 degrees C.
Kenneth Bartels, George Henry, D. Thomas Dickey, Ernest Stair, Ronald Powell, Steven Schafer, Robert Nordquist, Christopher Frederickson, Donald Hayes, David Wallace
Use of holmium laser energy for vaporization/coagulation of the nucleus pulposus in canine intervertebral discs has been previously reported and is currently being applied clinically in veterinary medicine. The procedure was originally developed in the canine model and intended for potential human use. Since the pulsed (15 Hz) holmium laser energy exerts photomechanical and photothermal effects, the potential for extrusion of additional disc material to the detriment of the patient is possible using the procedure developed for the dog. To reduce this potential complication, use of diode laser (805 nm - CW mode) energy, coupled with indocyanine green (ICG) as a selective laser energy absorber, was formulated as a possible alternative. Delivery of the ICG and diode laser energy was through a MicroJet device that could dispense dye interactively between individual laser 'shots.' Results have shown that it is possible to selectively ablate nucleus pulposus in the canine model using the device described. Acute observations (gross and histopathologic) illustrate that accurate placement of the spinal needle before introduction of the MicroJet device is critically dependent on the expertise of the interventional radiologist. In addition, the success of the overall technique depends on consistent delivery of both ICG and diode laser energy. Minimizing tissue carbonization on the tip of the MicroJet device is also of crucial importance for effective application of the technique in clinical veterinary medicine.
We have been evaluating the use of a pulsed Nd:YAG laser for ablating hard dental tissue. For this application we apply dye-drops of an IR absorptive fluid on the enamel, then irradiate with a laser pulse from the laser. By using ink- jet technology to deliver the dye-drops, we can attain micron- and millisecond-scale precision in drop delivery, with a 'burst' of drops preceding each laser pulse. To gain better understanding of the ablation process we have used a high- speed CCD camera system with 1 microsecond(s) exposure and 1 microsecond(s) inter-exposure-interval capability. Fast photography of the ablation process showed the following typical events. (i) The laser induced plasma plume erupts immediately after pulse onset, expands to maximum within 50 microsecond(s) , and lasts up to 200 microsecond(s) . (ii) Ejected particles flying away from the site of laser pulse/dye-drop impact are detected within 30 microsecond(s) of laser pulse onset, and continue up to 10 ms. These particles attain velocities up to 50 m/s with lower velocities from lower pulse power. (iii) The plasma plume has a peak height that increases with increasing laser fluence, ranging up to 10 mm for a fluence of 242 J/cm2 on enamel. From this study, the dye-assisted ablation mechanisms are inferred to be plasma-mediated and explosion- mediated tissue removal.
Christopher Frederickson, Quiang Lu, Donald Hayes, David Wallace, Michael Grove, Brent Bell, Massoud Motamedi, Sohi Rastegar, C. Wright, Charles Arcoria
Nd:YAG lasers have been used previously for selective removal of various material from teeth. To permit ablation of healthy enamel with the Nd:YAG laser, we have adopted a strategy in which micro-drops of photoabsorptive 'promoters' are placed on the enamel to enhance absorption of individual laser pulses. Ink-jet technology dispenses the micro-drops with micron- and millisecond-scale precision. Various promoters using drug and cosmetic dyes, indocyanine green, or carbon-black pigments have been studied. Typical ablation parameters are 1.064 micrometers ; 20-180 mJ per pulse; 100 microsecond(s) ; 10-30 pulses/sec; 0.2-2.0 nl drops. Recent results from the program include: (1) For a variety of promoters, a monotonic relationship obtains between absorption coefficient at 1.064 micrometers and the efficiency of ablation of enamel. (2) With different promoter volumes, the efficiency of ablation rises, plateaus, then falls with increasing volume. (3) At drilling rates of 30 pulses/sec, ablation efficiency approaches rates of 0.1 mm3/sec. LM and SEM observations show a glassy 'pebbled' crater surface indicative of hydroxyapatite that has cooled, condensed, and solidified on the crater walls. Together these results favor the view that a micro-drop promoter-assisted Nd:YAG drill can five clinically useful ablations hard dental tissue.
Organic dyes have found increasing use a s sensitizers in laser surgical procedures, due to their high optical absorbances. Little is known, however, about the nature of the degradation products formed when these dyes are irradiated with a laser. Previous work in our laboratories has shown that irradiation of polymeric and biological tissues with CO2 and Nd:YAG lasers produces a host of volatile and semivolatile by-products, some of which are known to be potential carcinogens. This work focuses on the identification of the chemical by-products formed by diode laser and Nd:YAG laser irradiation of indocyanine green (ICG) and carbon black based ink sensitized tissues, including bone, tendon and sheep's teeth. Samples were mounted in a 0.5-L Pyrex sample chamber equipped with quartz optical windows, charcoal filtered air inlet and an outlet attached to an appropriate sample trap and a constant flow pump. By-products were analyzed by GC/MS and HPLC. Volatiles identified included benzene and formaldehyde. Semi-volatiles included traces of polycyclic aromatics, arising from the biological matrix and inks, as well as fragments of ICG and the carbon ink components. The significance of these results will be discussed, including the necessity of using appropriate evacuation devices when utilizing lasers for surgical procedures.
The microjet printing method of micro-optical element fabrication is being used to make arrays of high-performance hemi-elliptical and hemi-cylindrical microlenses for potential use in applications such as collimation of edge-emitting diode laser array beams. The printing method enables both the fabrication of very fast (e.g., f/0.75) microlenses and the potential for reducing costs and increasing flexibility in micro-optics manufacture. The process for fabricating anamorphic microlenses, including those of square or rectangular shape, involves the dispensing and placing of precisely sized microdroplets of optical material onto optical substrates, and then controlling their coalescence and solidification. By varying the number, diameter and spacing of adjacent microdroplets of optical materials deposited at elevated temperatures onto heated substrate, both the dimensional aspect ratios and the ratio of `fast'- to-`slow' focal lengths of a printed hemi-elliptical microlens may be varied over a very wide range. Arrays of hemi-elliptical and hemi-cylindrical microlenses on the order of 100 - 300 micrometers in width and 150 micrometers to 20 mm long, with focal length ratios (fast/slow) from 1 (circular) to 0 (cylindrical), have been printed. A model for predicting printed hemi-elliptical microlens focal lengths from printed lenslet geometry is illustrated, along with an interferometric method of detecting lenslet defects and aberrations.
Microjet printing methods are being utilized for data-drive fabrication of micro-optical elements such as refractive lenslet arrays, multimode waveguides and microlenses deposited onto the tips of optical fibers. Materials used for microjet printing of micro-optics to date have included optical adhesives and index-tuned thermoplastic formulations dispensed at temperatures up to 200 degree(s)C onto optical substrates and components. By varying such process parameters as numbers and locations of deposited microdroplets, print head temperature and orifice size, and target substrate temperature and surface wetability, arrays of spherical and cylindrical plano-convex microlenses have been fabricated with dimensions ranging from 80 micrometers to 1 mm to precision levels of just a few microns, along with multimode channel waveguides. Optical performance data such as lenslet f/#s and far-field diffraction patterns are presented, along with beam-steering agility data obtained with an optical telescope system assembled from microlens arrays printed by this process.
Many laser medical procedures can be improved by dispensing exogenous fluids onto the tissue during irradiation. Examples include the dispensing of coolants, photoabsorptive enhancers, photoreflective tissue shields, photoactivated tissue solders, fillers, or surface sealants. The main obstacle to the use of such auxiliary fluids is the difficulty of dispensing them in a convenient, interactive fashion while operating the laser. We have adapted ink-jet printing technology to this problem of dispensing auxiliary fluids during laser procedures. The technology can dispense fluids with exquisite volumetric, spatial, and temporal precision. In principle, one or more fluids can be dispensed interactively from nozzles similar in size to the optical fibers and microlenses that are used for the lasers. Compact handpieces or endoscopic tools that will incorporate fluid MicroJets and laser optics can be envisioned. The enhancements to laser surgical technology that could be afforded by the use of fluid jetting will be discussed. Examples from ongoing work in dentistry, orthopedics, and dermatology are presented. Supported in part by NIH SBIR's DE10687 and GM50602.
Recent studies have established clinical application of laser ablation of cartilaginous tissue. The goal of this study was to investigate removal of cartilaginous tissue using diode laser. To enhance the interaction of laser light with tissue, improve the ablation efficiency and localize the extent of laser-induced thermal damage in surrounding tissue, we studied the use of a novel delivery system developed by MicroFab Technologies to dispense a known amount of Indocyanine Green (ICG) with a high spatial resolution to alter the optical properties of the tissue in a controlled fashion. Canine intervertebral disks were harvested and used within eight hours after collection. One hundred forty nL of ICG was topically applied to both annulus and nucleus at the desired location with the MicroJet prior to each irradiation. Fiber catheters (600 micrometers ) were used and positioned to irradiate the tissue with a 0.8 mm spot size. Laser powers of 3 - 10 W (Diomed, 810 nm) were used to irradiate the tissue with ten pulses (200 - 500 msec). Discs not stained with ICG were irradiated as control samples. Efficient tissue ablation (80 - 300 micrometers /pulse) was observed using ICG to enhance light absorption and confine thermal damage while there was no observable ablation in control studied. The extent of tissue damage observed microscopically was limited to 50 - 100 micrometers . The diode laser/Microjet combination showed promise for applications involving removal of cartilaginous tissue. This procedure can be performed using a low power compact diode laser, is efficient, and potentially more economical compared to procedures using conventional lasers.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.