Low-temperature microplasmas, efficient sources of ions, electrons, and photons, particularly from microcavity plasma arrays, offer unprecedented performance in photonics. This paper reports recent advancements across three key areas: precise timekeeping, achieved through integrating microplasma mercury ion lamps into miniature clock systems with exceptional stability; uniform and high-fluence photon generation for VUV photolithography and nanopatterning, enabling selective surface modification and low temperature dielectric depositions at nano/micro scales; and deep UV (Far UV-C) excimer emission from microplasma lamps, utilized in preventing airborne as well as foodborne pathogen transmission. Far UV-C's safety for human exposure presents potential for indoor disinfection, including wearable devices, shaping biothreat prevention strategies.
In this paper, far UV-C microplasma lamp with a flat form factor will be introduced for its performance to prevent airborne transmission of the virus by continuous viral density reduction in an indoor space. Unlike conventional UVC germicidal lights, which is harmful if it strikes the human body, far UVC (222 nm) photons from KrCl* excimer has recently been demonstrated to be harmless to human skin or eyes during direct exposure at occupied spaces.
Details concerning the lamp characteristics, effectiveness and safety studies, current applications, and prospects of the future use of the Far-UVC lamps will be discussed.
We report a novel, environmentally-friendly, scalable subtractive process which allows for complex 3D optical, microfluidic and biomedical components and microstructures to be fabricated precisely in a wide variety of polymers.
The reported technique is capable of producing submicron structures with <20 nm depth precision in common polymers (PMMA, ABS, etc.) as well as microchannels and 3D surfaces of >20 µm depth in biodegradable polymers. The process is based on a VUV (λ=172 nm) photoablative lithographic technique utilizing flat microplasma lamps and does not require a clean room environment or any chemical processing. The fabricated 3D surface may also be used as a mold for PDMS curing.
Complex 3D structures having lateral and depth resolutions of <1 µm and 20 nm, respectively, are fabricated in various polymers, including PMMA, ABS, CR-39, and others, by a direct photoablation process utilizing 172 nm radiation from flat microplasma-driven excimer lamps. The developed process does not require any toxic or photosensitive materials, and, therefore, may be performed outside of a clean room. The fabricated 3D structures may also serve as a master mold for PDMS and the curing of other materials.
Gratings, Fresnel lenses, phase masks, and waveguides are among the optical components that have been fabricated by 172 nm irradiation of various polymers through photomasks. Intensities above ~ 70 mW/cm^2 are now commercially available at 172 nm with flat Xe2 lamps. Such optical fluences are capable of precisely (< 500 nm lateral and 20 nm depth resolution) ablating a wide range of polymers, including PMMA and ABS, thereby allowing for a variety of 3D optical and biomedical components to be realized economically by dry processing.
Photolithographic techniques capable of producing sub-micron scale features typically involve laser or electron beam sources and chemical development of an exposed photoresist. We report here a novel, low cost photolithographic process utilizing flat, efficient lamps emitting at 172 nm. Recently developed 10 cm x 10 cm lamps, for example, produce more than 25 W of average power at 172 nm which enables the precise and fast patterning of most polymers, including those normally employed as e-beam resists and photoresists. Recent experiments demonstrate that PMMA films less than 100 nm in thickness are patterned in less than 20 s through a contact mask with high contrast resolution of 500 nm features. The ultimate resolution limit is expected to be ≤ 300 nm for a contact method. Electroplating technique was further used to deposit 500 nm gold features on a silicon substrate. The reported process does not require a photoresist development step and is performed in nitrogen atmosphere at atmospheric pressure which make it fast and affordable for fabrication facilities that have no access to high-tech photolithography equipment. Samples as large as 76 mm (3”) in diameter may be exposed with a single lamp in one step and areas of 1 m2 and above may be processed with tiled arrays of lamps.
Patterning of bulk polymers (acrylic sheets, for example) through a photomask and subsequent formation of sub-micron features has also been demonstrated.
Flat UV lamps comprising large arrays of microcavity plasmas, and capable of efficiently generating in the wavelength from VUV to UV-B radiation, have been developed by the team of University of Illinois and Eden Park Illumination. UV light is desirable for a number of chemical processes and disinfection methods available commercially but conventional UV light sources suffer from several drawbacks, including undesirable form factors and operational concerns regarding the use of mercury. Microplasmas are non-equilibrium, low-temperature plasma sources which have high power loading (several hundred kW/cm3), thereby enabling them to efficiently form UV-generating excimer molecules. This work has focused on leveraging microplasma array technology to realize low-temperature UV lamps that are flat and designed to have a scalable, slim form factor (total thickness less than ~5 mm). Each microcavity (less than a sub-millimeters in its cross-sectional dimensions) was fabricated through a series of microfabrication techniques, and the spatial variation of the electric field strength in each microcavity was tailored through the cavity cross-section and electrode geometry to efficiently generate deep UV radiation. UV light tiles capable of producing fluences up to 200 mW/cm2 at 172 nm which generates more than 25 watts of average power from a lamp of only 16 square inches in active surface area. Details concerning lamp performance of UV lamps having emitting wavelengths specifically in 146, 172, 222, and 308 nm will be discussed. The potential applications of the microplasma UV lighting tiles such as photochemistry, semiconductor processes, environmental and biomedical applications will be discussed.
The results of testing two technologies based on gas microplasmas for the generation of UV-visible light is
detailed. A microcavity device from the University of Illinois at Champaign-Urbana have been delivered with an Ar/D2
gas mixture. Emission from the Ar/Ne as well as an Ar/D2 eximer in the 250-400nm range, as well as argon lines in the
visible and near infrared, are measured. Development of addressing arrays is discussed as is the potential of emission in
other wavebands with other gas species. A 100x40 array of plasmaspheres combined with electronics capable of
projecting images at 1000 Hz with 10 bits of grayscale resolution has been built and tested. This system, built by
Imaging Systems Technology (IST), is capable of accepting DVI output from a HWIL system and projecting UV from a
gas captured in the spheres. This array uses an argon neon gas mixture to produce UV, visible and near infrared light.
Performance data discussed for both arrays include: maximum and minimum brightness, uniformity, spectral content,
speed, linearity, crosstalk, resolution, and frame rate. Extensions of these technologies to larger arrays with wider
spectral bandwidth for use in multispectral projectors are discussed.
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.