"Hard-scattering" approach to very hindered magnetic-dipole transitions in quarkonium

For a class of hindered magnetic dipole ($M1$) transition processes, such as $\Upsilon(3S)\to \eta_b+\gamma$ (the discovery channel of the $\eta_b$ meson), the emitted photon is rather energetic so that the traditional approaches based on multipole expansion may be invalidated. We propose that a "hard-scattering" picture, somewhat analogous to the pion electromagnetic form factor at large momentum transfer, may be more plausible to describe such types of transition processes. We work out a simple factorization formula at lowest order in the strong coupling constant, which involves convolution of the Schr\"odinger wave functions of quarkonia with a perturbatively calculable part induced by exchange of one semihard gluon between quark and antiquark. This formula, without any freely adjustable parameters, is found to agree with the measured rate of $\Upsilon(3S)\to \eta_b+\gamma$ rather well, and can also reasonably account for other recently measured hindered $M1$ transition rates. The branching fractions of $\Upsilon(4S)\to \eta_b^{(\prime)}+\gamma$ are also predicted.Comment: v3; 5 pages, 1 figure and 1 table; title changed, presentation improve

Current commercialization status of electrowetting-on-dielectric (EWOD) digital microfluidics.

The emergence of electrowetting-on-dielectric (EWOD) in the early 2000s made the once-obscure electrowetting phenomenon practical and led to numerous activities over the last two decades. As an eloquent microscale liquid handling technology that gave birth to digital microfluidics, EWOD has served as the basis for many commercial products over two major application areas: optical, such as liquid lenses and reflective displays, and biomedical, such as DNA library preparation and molecular diagnostics. A number of research or start-up companies (e.g., Phillips Research, Varioptic, Liquavista, and Advanced Liquid Logic) led the early commercialization efforts and eventually attracted major companies from various industry sectors (e.g., Corning, Amazon, and Illumina). Although not all of the pioneering products became an instant success, the persistent growth of liquid lenses and the recent FDA approvals of biomedical analyzers proved that EWOD is a powerful tool that deserves a wider recognition and more aggressive exploration. This review presents the history around major EWOD products that hit the market to show their winding paths to commercialization and summarizes the current state of product development to peek into the future. In providing the readers with a big picture of commercializing EWOD and digital microfluidics technology, our goal is to inspire further research exploration and new entrepreneurial adventures

Low-cost and low-topography fabrication of multilayer interconnections for microfluidic devices

Multilayer interconnections are needed for microdevices with a large number of independent electrodes. A multi-level photolithographic process is commonly employed to provide multilayer interconnections in integrated circuit (IC) devices, but it is often too expensive for large-area or disposable devices frequently needed for microfluidics. The printed circuit board (PCB) can provide multilayer interconnection at low cost, but its rough topography poses a challenge for small droplets to slide over. Here we report a low-cost fabrication of low-topography multilayer interconnects by selective and controlled anodization of thin-film metal layers. The process utilizes anodization of metal (tantalum in this paper) or, more specifically, repetitions of a partial anodization to form insulation layers between conductive layers and a full anodization to form isolating regions between electrodes, replacing the usual process of depositing, planarizing, and etching insulation layers. After verifying the electric connections and insulations as intended, the developed method is applied to electrowetting-on-dielectric (EWOD), whose complex microfluidic products are currently built on PCB or thin-film transistor (TFT) substrates. To demonstrate the utility, we fabricated a 3 metal-layer EWOD device with steps (surface topography) less than 1 micrometer (vs. > 10 micrometers of PCB EWOD devices) and confirmed basic digital microfluidic operations