Research Terms
Researchers at the University of Central Florida have developed a method for creating uniform, highly spherical particles as small as a few nanometers in diameter. The new technology forms particles by applying heat to a multi-layer fiber, drawing the core into uniform spheres within the outer layer. Specifiable to any application, the particles can be created from a variety of materials, such as glass, polymers, liquids, and metals, and in a wide range of sizes, from sub-millimeter to the tens of nanometers. The formation method enables the controllable and scalable production of complex, well-defined micro-scale and nano-scale structures that are well-ordered, controllably oriented, and immobilized.
Technical Details
Particles are created from multi-material fibers drawn near the plasticity temperature, "melting" the core into an evenly-spaced sequence of uniform droplets while still encased in an unaffected outer layer of a higher softening temperature material. The breakup process of the core is not based on chemistry, but on the physical parameters of viscosity and surface tension in the presence of specifically calculated temperature as determined by the Plateau-Rayleigh instability. As such, the materials used are chosen for their mechanical and melting compatibility for a given particle property and size. The core particles' size is determined by controlling tapering speed during the drawing process. As the combination of materials cools, the material of the particles solidifies within the outer layer of the fiber, which can be left as-is or dissolved to release the particles.
Researchers at the University of Central Florida have developed a method for fabricating chalcogenide glass fiber preforms: one-step multi-material extrusion. Silica optical fibers are the industry standard for communication wavelengths due to their high optical quality and reliability, however, these fibers have a limited transmission window and cannot be used for mid-infrared (MIR) light applications. Fibers used in MIR applications can benefit from the optical functionality of chalcogenide (ChG) glasses, which are highly transparent in the infrared spectrum of interest and have attracted interest for MIR beam delivery, imaging fiber bundles, and nonlinear optics. However, the extremely brittle nature of ChG complicates handling and processing necessary to draw the material into fibers. Conventional attempts to use a polymer layer have been confined by the limited working temperature and an inability to co-draw the materials necessary for a robust ChG optical fiber.
Technical Details
The UCF invention consists of new ChG fiber with a polymer jacket harnesses the mechanical strength of the polymer without compromising the optical functionality of ChG. The optical properties of the fiber are determined by the ChG, while the mechanical properties are determined by the polymer. By separating the functionalities this way, each can be optimized independently. The new fiber is extruded under pressure, allowing the use of lower temparatures and higher viscosities compared to fiber drawing, thereby reducing glass crystallization. The polymer protects the fragile ChG from contacting the die during extrusion or subsequently with the ambient environment and allows for convenient handling and reduced aging of the fiber but does not participate in the optical functionality of the fiber, determined by the ChG alone.
Researchers at the University of Central Florida have developed an apparatus and methods for achieving omniresonant broadband coherent perfect absorption (CPA) in a structure. With the ability to provide maximum absorption across extended bandwidths, the invention enables achromatic optical absorption (omniresonance spanning greater than 50 nm, CPA). Existing technologies require modifying the cavity by inserting a new material or structure with a sculpted dispersion profile. Thus, those technologies only support the exploration of macroscopic white-light cavities.
The UCF invention enables 100% effective optical absorption—regardless of the material from which it is constructed—over a large, continuous bandwidth (omniresonance) in ultrathin devices. The inspriation for this design is the reverse-color diffraction observed in the wings of the Moon Satyr butterfly, Pierella luna, enabling “anomalous diffraction”. Example applications include the following:
Technical Details
The UCF invention provides a structure, systems and methods for achieving omniresonant broadband coherent perfect absorption (CPA) in a planar Fabry-Pérot microcavity. It employs angularly multiplexed phase-matching that exploits a bioinspired grating configuration. By assigning each wavelength to an appropriate angle of incidence, the microcavity can absorb with continuous spectral range. For example, the linewidth of a single-order 0.7 nm wide resonance is de-slanted in spectral-angular space to become a 70 nm wide achromatic resonance spanning multiple cavity-free spectral ranges.
Figure 1 illustrates the following: (a) Using a ‘black-box
system’ correlating ? with ?, a planar micro-cavity is made transparent. The
inverse is placed after the cavity to restore the original beam. (b) Solid
curves are target correlations between ? and ? that help de-slant different
resonant mode-orders in a planar micro-cavity. The dashed curve corresponds to
the correlation imparted to a collimated broadband beam centered at ?c=550 nm
that is incident normally on a planar surface grating having 1800 lines/mm. (c)
Angular diffraction resulting from a planar surface grating parallel and (d)
normal to the plane of a cavity.
Figure 2 illustrates the following: (a) Measured spectral transmission of collimated light through the cavity with angle of incidence ? for both polarizations. The transmission is symmetric in ? for TE (H: horizontal) and TM (V: vertical) polarizations, so measurements for only positive ? are plotted. Inset is a schematic of the configuration. (b) Experimental setup. L1 and L2 are lenses, OSA: optical spectrum analyzer; see main text and Supplement 1 for details. Inset is a photograph of the resonator showing strong reflectivity in the visible (cavity sample diameter is 25 mm).
Partnering Opportunity
The research team is looking for partners to develop the technology further for commercialization.
Stage of Development
Proof of principle.
Omni-resonant optical micro-cavity, Scientific Reports 7, 10336 (2017). https://doi.org/10.1038/s41598-017-10429-4.
Researchers at the University of Central Florida have developed technologies that manufacturers and designers can use to produce ChroMorphous® fabric for clothing and textiles. The e-textile innovation enables a user to change colors and patterns on demand. For example, a person wearing a shirt and slacks made with ChroMorphous® can use her smartphone to change the colors and patterns without switching to another outfit. The same applies to a purse or backpack to match the outfit. Unlike existing color-changing technologies, the UCF inventions do not depend on a wearer’s body heat, a room’s ambient temperature, or sunlight to work. ChroMorphous® is like traditional fabric—cut it, sew it, wash and iron it. Various applications include fashion and accessories, upholstery, medical, defense, and artistic uses.
The UCF inventions comprise dynamically-controllable color-changing fibers, fabrics, products, and manufacturing methods. In one example application, a color-changing monofilament has an electrically conductive core or multi-core and a coating around and along the core. The coating includes a layer of polymeric material with a color-changing pigment, for example, a thermochromic pigment. The monofilament can be a filament, a strand, or a fiber twisted or braided into a multifilament (such as yarn or thread). In turn, the multifilament can be stitched, sewn, or embroidered onto an existing fabric or product. It can also be woven to form a new fabric or product. The coating can include one or more layers, each with different color-changing portions or segments and thermochromic pigment.
A control system (the controller) operates the color-changing product. The controller can include a control device with a processing circuit such as an application-specific integrated circuit (ASIC) and a power supply, such as a lithium battery. During operation, an electrical current (provided by a power source such as a battery, a solar panel, a photovoltaic fiber) passes through the core. The resistance of the core to the electrical current causes the temperature of the core to elevate and thereby activate the thermochromic pigment of the coating to transition from one color to another color (for example, from a darker color to a lighter color or from one opaque color to a different opaque color). In some embodiments, the color-changing fiber transitions in tens or hundreds of milliseconds (depending on the amount of power applied). The color-changing fiber may operate at low voltages (for example, 12 volts or less).
An example manufacturing method includes loading a polymeric material and a thermochromic pigment material (both raw materials) into a fiber fabrication machine that comprises an extruder and a spinneret. During production, the extruder provides a molten mixture of the polymeric material and the thermochromic pigment material to the spinneret. In turn, the spinneret coats an electrically conductive core with the molten mixture to produce the color-changing fiber.
The research team is looking for partners to develop the technology further for commercialization.
Prototype available.
Researchers at the University of Central Florida have developed a way to increase the broadband optical absorption of thin-film solar cells regardless of their thickness or intrinsic absorption. Thin-film technologies (less than 10 um) reduce the material cost of solar cells and provide added flexibility. However, their reduced light absorption capacity results in lower cell efficiency.
To resolve this issue, the UCF researchers designed a layered solar-energy apparatus that uniquely combines the effects of coherent perfect absorption (CPA) and omniresonance optical phenomena. Thus, the invention improves the power conversion efficiency of solar cells independent of the materials used. Experimental results indicate that the apparatus achieved an increased external quantum efficiency (EQE) of 90 percent of the photocurrent generated in the 80 nm near-infrared (NIR) region from 660-740 nm, as compared to a bare solar cell.
Technical Details
The invention design consists of a visibly transparent planar structure that uses a CPA scheme to boost the absorption of a multilayer thin-film configuration. The configuration requires no surface patterning to overcome the intrinsic absorption limitation of the absorbing material. Besides planar structures, the device design strategy can also apply to on-chip implementations for efficient on-chip optical detection, strong-coupling with resonant materials, and the ultra-sensitive detection of pathogens.
Partnering Opportunity
The research team is looking for partners to develop the technology further for commercialization.
Stage of Development
Prototype available.