Publications by authors named "Regan Watts"

Modern cell and developmental biology increasingly relies on 3D cell culture systems such as organoids. However, routine interrogation with microscopy is often hindered by tedious, non-standardized sample mounting, limiting throughput. To address these bottlenecks, we have developed a pipeline for imaging intact organoids in flow, utilizing a transparent agarose fluidic chip that enables efficient and consistent recordings with theoretically unlimited throughput.

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Soft lithography has long remained the state of the art to generate the necessary micropatterning for molded microfluidic (MF) chips. Previous attempts to use printed circuit boards (PCBs) as a cheap and accessible alternative to expensive lithographed molds for the production of PDMS MF chip prototypes have shown their limitations. A more in-depth exploration of using PCBs as a mold substrate and a novel methodology of using flexible PCBs to produce highly accurate MF chips is reported here for the first time.

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To study the biodistribution of new chemical and biological entities, an in vitro model of the blood-brain barrier (BBB) may become an essential tool during early phases of drug discovery. Here, we present a proof-of-concept of an in-house designed three-dimensional BBB biochip designed by us. This three-dimensional dynamic BBB model consists of endothelial cells and astrocytes, co-cultured on opposing sides of a polymer-coated membrane under flow mimicking blood flow.

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Introduction: The COVID-19 pandemic significantly increased the usage of various types of face masks. In addition, it triggered the rapid manufacture of new production lines of masks to cope with the unprecedented demand to overcome worldwide shortages. Such masks, which were previously used mostly by the health care personnel, became a daily necessity to the greater mainstream population.

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Wearable electrochemical sensors are driven by the user-friendly capability of on-site detection of key biomarkers for health management. Despite the advances in biomolecule monitoring such as glucose, still, several unmet clinical challenges need to be addressed. For example, patients suffering from phenylketonuria (PKU) should be able to monitor their phenylalanine (PHE) level in a rapid, decentralized, and affordable manner to avoid high levels of PHE in the body which can lead to a profound and irreversible mental disability.

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The SARS-CoV-2 pandemic presented European hospitals with chronic shortages of personal protective equipment (PPE) such as surgical masks and respirator masks. Demand outstripped the production capacity of certified European manufacturers of these devices. Hospitals perceived emergency local manufacturing of PPE as an approach to reduce dependence on foreign supply.

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The optical outputs of single-section quantum-dash and quantum-dot mode-locked lasers (MLLs) are well known to exhibit strong group velocity dispersion. Based on careful measurements of the spectral phase of the pulses from these MLLs, we confirm that the difference in group delay between the modes at either end of the MLL spectrum equals the cavity round-trip time. This observation allows us to deduce an empirical formula relating the accumulated dispersion of the output pulse to the spectral extent and free-spectral range of the MLL.

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Successful use of a single-section quantum well (QW) passively mode-locked laser (MLL) as a comb source for optical interconnects is demonstrated for the first time. Sixteen comb lines spaced by 37.6 GHz are modulated using 25 Gb/s compatible single sideband orthogonal frequency division multiplexed (SSB-OFDM) signals and transmitted over 50 km of standard single-mode fiber with bit error ratio below the 7% forward error correction limit.

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Terabit/s super-channels are likely to become the standard for next-generation optical networks and optical interconnects. A particularly promising approach exploits optical frequency combs for super-channel generation. We show that injection locking of a gain-switched laser diode can be used to generate frequency combs that are particularly well suited for terabit/s super-channel transmission.

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We use the physics of four-wave mixing to study the decorrelation of two optical frequencies as they propagate through different fiber delays. The phase noise relationship between the four-wave mixing components is used to quantify and measure the correlation between the two optical frequencies using the correlation coefficient. We show the difference in the evolution of decorrelation between frequency-dependent and frequency-independent components of phase noise.

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We study the effect of transfer of phase noise in different four wave mixing schemes using a coherent phase noise measurement technique. The nature of phase noise transfer from the pump to the generated wavelengths is shown to be independent of the type of phase noise (1 / f or white noise frequency components). We then propose a novel scheme using dual correlated pumps to prevent the increase in phase noise in the conjugate wavelengths.

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This research carries out coherence measurements of a 42.7 GHz quantum dash (QDash) semiconductor laser when passively, electrically, and optically mode-locked. Coherence of the spectral lines from the mode-locked laser is determined by examining the radio frequency beat-tone linewidth as the mode spacing is increased up to 1.

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The mode coherence of adjacent and non-adjacent spectral modes of a passively mode locked quantum dash (QDash) semiconductor laser are deduced through radio frequency beat-tone linewidth measurements. A wavelength conversion scheme that uses degenerate four wave mixing in a semiconductor optical amplifier is proposed which considerably extends the mode spacing beyond the limit imposed by conventional fast-photodetection and electrical spectrum analysis of around 100 GHz. Using this scheme, the mode coherence of the QDash laser was measured out to the thirty-first harmonic, or a mode separation of 1.

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