Fabrication and characterization of a two-dimensional individually addressable electrowetting microlens array: erratum.

The authors present an erratum to update the Acknowledgements section in their published article, ["Fabrication and characterization of a two-dimensional individually addressable electrowetting microlens array," Opt. Express31, 30550 (2023)10.1364/OE.497992].

Fabrication and characterization of a two-dimensional individually addressable electrowetting microlens array.

We demonstrate a two-dimensional, individually tunable electrowetting microlens array fabricated using standard microfabrication techniques. Each lens in our array has a large range of focal tunability from -1.7 mm to -∞ in the diverging regime, which we verify experimentally from 0 to 75 V for a device coated in Parylene C. Additionally, each lens can be actuated to within 1% of their steady-state value within 1.5 ms. To justify the use of our device in a phase-sensitive optical system, we measure the wavefront of a beam passing through the center of a single lens in our device over the actuation range and show that these devices have a surface quality comparable to static microlens arrays. The large range of tunability, fast response time, and excellent surface quality of these devices open the door to potential applications in compact optical imaging systems, transmissive wavefront shaping, and beam steering.

Axisymmetrical resonance modes in an electrowetting optical lens.

Electrowetting-based adaptive optics are of great interest for applications ranging from confocal microscopy to LIDAR, but the impact of low-frequency mechanical vibration on these devices remains to be studied. We present a simple theoretical model for predicting the resonance modes induced on the liquid interface in conjunction with a numerical simulation. We experimentally confirm the resonance frequencies by contact angle modulation. They are found to be in excellent agreement with the roots of the zero-order Bessel functions of the first kind. Next, we experimentally verify that external axial vibration of an electrowetting lens filled with density mismatched liquids (Δρ = 250 kg/m3) will exhibit observable Bessel modes on the liquid-liquid interface. An electrowetting lens filled with density matched liquids (Δρ = 4 kg/m3) is robust to external axial vibration and is shown to be useful in mitigating the effect of vibrations in an optical system.

Adaptive aberration correction using an electrowetting array.

We demonstrate a method that permits wavefront aberration correction using an array of electrowetting prisms. A fixed high fill factor microlens array followed by a lower fill factor adaptive electrowetting prism array is used to correct wavefront aberration. The design and simulation of such aberration correction mechanism is described. Our results show significant improvement to the Strehl ratio by using our aberration correction scheme which results in diffraction limited performance. Compactness and effectiveness of our design can be implemented in many applications that require aberration correction, such as microscopy and consumer electronics.

Longitudinal Study Comparing Mental Health Outcomes in Frontline Emergency Department Healthcare Workers through the Different Waves of the COVID-19 Pandemic.

As countries transition from the COVID-19 pandemic to endemic status, healthcare systems continue to be under pressure. We aimed to quantify changes in depression, anxiety, stress and post-traumatic stress disorder (PTSD) between 3 cohorts (2020, 2021 and 2022) of our Emergency Department (ED) healthcare workers (HCWs) and those who had worked through all 3 phases of the pandemic; and identify factors associated with poorer mental health outcomes (MHOs). In this longitudinal single-centre study in Singapore, three surveys were carried out yearly (2020, 2021 and 2022) since the COVID-19 outbreak. Depression, anxiety and stress were measured using DASS-21, and PTSD was measured using IES-R. A total of 327 HCWs (90.1%) participated in 2020, 279 (71.5%) in 2021 and 397 (92.8%) in 2022. In 2022, ED HCWs had greater concerns about workload (Mean score ± SD: 2022: 4.81 ± 0.86, vs. 2021: 4.37 ± 0.89, vs. 2020: 4.04 ± 0.97) and perceived to have less workplace support (2022: 4.48 ± 0.76, vs. 2021: 4.66 ± 0.70, vs. 2020: 4.80 ± 0.69). There was overall worsening depression (27.5% in 2020, 29.7% in 2021 and 32.2% in 2022) and stress (12.2% in 2020, 14.0% in 2021 and 17.4% in 2022). Healthcare assistants as a subgroup had improving MHOs. ED HCWs who were female and had psychiatric history, were living with the elderly, and had concerns about their working environment, workload and infection had poorer MHOs. This study will guide us in refining existing and devising more focused interventions to further support our ED HCWs' wellbeing.

Spectrally tunable liquid resonator based on electrowetting.

We present a tunable on-chip liquid resonator in conjunction with a tapered fiber coupling scheme. The resonator consists of a glycerol droplet submerged within an immiscible liquid bath, which mitigates the effects of environmental fluctuations. The platform is fabricated using standard semiconductor techniques, which enable the future integration of photonic components for an on-chip liquid resonator device. The liquid resonator maintains its high Q-factor on chip (105) due to surface tension forming an atomically smooth liquid-liquid interface. Higher Q-factor resonance modes experienced linewidth broadening due to the random excitation of thermal capillary vibrations. Spectral tuning is demonstrated using the electrowetting effect, increasing the surface's wettability and an expansion in the droplet diameter. A maximum spectral tuning of 1.44 nm ± 5 pm is observed by applying 35 V. The tuning range is twice the free spectral range (FSR) of 0.679 nm measured at a pumping wavelength range of 770-775 nm. A 2D axisymmetric finite-element simulation shows resonance modes in good agreement with experimentally measured spectra and with predicted tuning speeds of 20 nm/s.

SARS-CoV-2 in wastewater: From detection to evaluation.

SARS-CoV-2 presence in wastewater has been reported in several studies and has received widespread attention among the Wastewater-based epidemiology (WBE) community. Such studies can potentially be used as a proxy for early warning of potential COVID-19 outbreak, or as a mitigation measure for potential virus transmission via contaminated water. In this review, we summarized the latest understanding on the detection, concentration, and evaluation of SARS-CoV-2 in wastewater. Importantly, we discuss factors affecting the quality of wastewater surveillance ranging from temperature, pH, starting concentration, as well as the presence of chemical pollutants. These factors greatly affect the reliability and comparability of studies reported by various communities across the world. Overall, this review provides a broadly encompassing guidance for epidemiological study using wastewater surveillance.

Strategy for Safe Bronchoscopy During the COVID-19 Pandemic.

Aerosol-generating procedures are avoided for patients with coronavirus disease 2019 (COVID-19) to lower the risk of transmission to health care providers. However, when bronchoscopy is indicated, it remains unclear whether the procedure performed while the patient is under general anesthesia leads to contamination of the surroundings and whether standard endoscopy reprocessing methods are effective in eradicating severe acute respiratory syndrome coronavirus 2. This report describes a case of bronchoscopic retrieval of a foreign body in the airway of a patient under general anesthesia who tested positive for COVID-19. The report focuses on anesthesia techniques to minimize aerosolization.

Predictors of obstructive sleep apnea misclassification when using total bed time versus total sleep time.

Obstructive sleep apnea (OSA) is a highly prevalent condition worldwide. Untreated, it is associated with multiple medical complications as well as a reduced quality of life. Home sleep apnea tests are increasingly used for its diagnosis and evaluation of severity, but using total bed time rather than total sleep time may underestimate OSA severity. We aim to uncover the extent and predictors of OSA misclassification when using total bed time. A retrospective observational study was conducted using data from the sleep laboratory of the National University Hospital, Singapore, a tertiary hospital with 1200 beds. Misclassification of OSA was defined as any OSA severity that was less severe using total bed time versus total sleep time. Logistic regression was used to identify predictors of OSA misclassification. A total of 1621 patients were studied (mean age 45.6 ± 15.9 years; 73.4% male). 300 (18.5%) patients were misclassified. Risk factors for OSA misclassification included age (OR 1.02, 95% CI 1.01-1.03, P = 0.001) and body-mass index (BMI) (OR 0.97, 95% CI 0.95-0.99, P = 0.015). Risk for misclassification was significant in patients aged ≥ 57 years old, with BMI < 32.3 kg/m2. Using total bed time rather than total sleep time to quantify OSA severity was associated with a significant risk of misclassification, particularly in patients aged ≥ 57 years old, with BMI < 32.3 kg/m2.

POCUS in cardiac arrest and its therapeutic implications - a case report.

Point of Care Ultrasound is an increasingly popular modality in the emergency department as well as in the critical care unit. Its applications are varied, centered on its role in diagnosis, thereby minimizing the time taken for the appropriate diagnosis to be made and hence incorporate definitive treatment. There are currently no international guidelines published with regards for point of care ultrasound in the context of cardiac arrest. We propose to delineate the impact of the role of point of care ultrasound in a patient with cardiac arrest, in the evaluation of the cause, its prognostic role, as well as possible implications for therapies based on a case report.

Pre-operative MRI measurements versus anthropometric data: Which is more accurate in predicting 4-stranded hamstring graft size in anterior cruciate ligament reconstruction?

BACKGROUND/OBJECTIVE: Graft diameter has been shown to play an important role in anterior cruciate ligament (ACL) autograft failure rates. The roles of pre-operative MRI measurement of graft size and anthropometric data have been studied in the prediction of hamstring graft size. Pre-operative knowledge of hamstring graft diameter allows surgeons to perform better surgical planning and provides an opportunity to discuss with patients on alternative graft options such as allografts should the need arises. The purpose of this study was to compare the accuracy of pre-operative anthropometric data and MRI measurements in the prediction of 4-stranded hamstring autograft size in anterior cruciate ligament reconstruction. METHOD: This was a cohort study involving 141 subjects (115 males and 26 females) who underwent a single bundle ACL reconstruction utilising a 4-stranded hamstring graft by a single surgeon from 2008 to 2012. Pre-operatively, the height, weight, body mass index (BMI), age, gender and smoking status was recorded. The MRI scans used for diagnosis were utilized to measure the gracilis (GT) and semi-tendinosus (ST) cross sectional area (CSA). RESULT: We found the strongest correlation between Combined (ST + GT) CSA and intra-operative graft size (r = 0.596, p < 0.001). This was followed by ST CSA (r = 0.570,p < 0.001), Body surface area (r = 0.507,p < 0.001), and GT CSA (r = 0.460,p < 0.001). No significant correlation was found between 2 anthropometric data (Age and BMI). There was also no significant difference between different strengths of MRIs (1.5T vs 3.0T) in determining the intra-operative graft size (p = 0.438). CONCLUSION: We conclude that pre-operative MRI is superior to anthropometric variables in predicting the size of 4-stranded hamstring autografts used in ACL reconstruction.

Four Patients with COVID-19 and Tuberculosis, Singapore, April-May 2020.

Coronavirus disease (COVID-19) and tuberculosis (TB) developed in 4 foreign workers living in dormitories in Singapore during April-May 2020. Clinical manifestations and atypical radiographic features of COVID-19 led to the diagnosis of TB through positive interferon-gamma release assay and culture results. During the COVID-19 pandemic, TB should not be overlooked.

Calibration and characteristics of an electrowetting laser scanner.

We present a calibration method to correct for fabrication variations and optical misalignment in a two-dimensional electrowetting scanner. These scanners are an attractive option due to being transmissive, nonmechanical, having a large scan angle (±13.7°), and low power consumption (µW). Fabrication imperfections lead to non-uniform deposition of the dielectric or hydrophobic layer which results in actuation inconsistency of each electrode. To demonstrate our calibration method, we scan a 5 × 5 grid target using a four-electrode electrowetting prism and observe a pincushion type optical distortion in the imaging plane. Zemax optical simulations verify that the symmetric distortion is due to the projection of a radial scanning surface onto a flat imaging plane, while in experiment we observe asymmetrical distortion due to optical misalignment and fabrication imperfections. By adjusting the actuation voltages through an iterative Delaunay triangulation interpolation method, the distortion is corrected and saw an improvement in the mean error across 25 grid points from 43 µm (0.117°) to 10 µm (0.027°).

Lidar system with nonmechanical electrowetting-based wide-angle beam steering.

A light detection and ranging (lidar) system with ±90° of steering based on an adaptive electrowetting-based prism for nonmechanical beam steering has been demonstrated. Electrowetting-based prisms provide a transmissive, low power, and compact alternative to conventional adaptive optics as a nonmechanical beam scanner. The electrowetting prism has a steering range of ±7.8°. We demonstrate a method to amplify the scan angle to ±90° and perform a one-dimensional scan in a lidar system.

Liquid Combination with High Refractive Index Contrast and Fast Scanning Speeds for Electrowetting Adaptive Optics.

Electrowetting adaptive optical devices are versatile, with applications ranging from microscopy to remote sensing. The choice of liquids in these devices governs its tuning range, temporal response, and wavelength of operation. We characterized a liquid system, consisting of 1-phenyl-1-cyclohexene and deionized water, using both lens and prism devices. The liquids have a large contact angle tuning range, from 173 to 60°. Measured maximum scanning angle was realized at ±13.7° in a two-electrode prism, with simulation predictions of ±18.2°. The liquid's switching time to reach 90° contact angle from rest, in a 4 mm diameter device, was measured at 100 ms. Steady-state scanning with a two-electrode prism showed linear and consistent scan angles of ±4.8° for a 20 V differential between the two electrodes, whereas beam scanning using the liquid system achieved ±1.74° at 500 Hz for a voltage differential of 80 V.

Comparative study of magnetic resonance imaging (MRI) parameters in a Southeast Asian population with symptomatic patellofemoral instability.

BACKGROUND: MRI is performed for evaluation of soft tissue injuries associated with patellar instability. METHODS: Retrospective review of MRI parameters from a study group of 64 patients with symptomatic patellofemoral instability and a control group of 64 patients with acute knee injury without concomitant patellofemoral instability was performed. RESULTS: The study group demonstrated statistically significant increase (P<0.05) in all the MRI measurements compared to the control group. There were good inter-observer correlations between surgeon and radiologist for all radiological measurements. CONCLUSIONS: It is prudent to exercise caution in interpreting radiological parameters in different ethnic groups bearing as current treatment protocols are not ethnic-group specific.

Radiological features of a rare case of pancreatic panniculitis presenting in bilateral lower extremities.

Pancreatic panniculitis is a rare cutaneous presentation in patients with pancreatic pathology. While it presents as cutaneous inflammation with painful and erythematous nodules which demonstrate ulceration, imaging features of this pathology are seldom described. The common sites of involvement are the extremities. It demonstrates characteristic histological features of lobular panniculitis with ghost cells. MR imaging with its excellent soft tissue contrast can be helpful in confirming the diagnosis, demonstrating imaging features of fat necrosis with surrounding inflammation as demonstrated in our patient.

Neuroendocrine adenoma of middle ear with new bone formation and review of literature.

Neuroendocrine adenoma of the middle ear has been described in literature as middle ear adenoma with neuroendocrine differentiation or carcinoid tumor. While there have been several case reports describing imaging features of carcinoid tumors of the ear and middle ear adenomas, in our literature review, we have not found a single case where bone formation is described as a prominent radiological feature. We report a first documented case of middle ear carcinoid tumor with new bone formation demonstrated on CT imaging and performed a review literature regarding the tumor. A differential diagnosis of neuroendocrine adenoma of the middle ear should be considered when there is prominent bone formation with a soft tissue mass in the middle ear on CT imaging.

In situ photo-assisted deposition and photocatalysis of ZnIn2S4/transition metal chalcogenides for enhanced degradation and hydrogen evolution under visible light.

The effective immobilization of a transition chalcogenide co-catalyst via an in situ aqueous photo-assisted deposition technique has shown great accessibility to complex ZnIn2S4 host hierarchical nanostructured materials with homogeneous distribution. The complementary photo-assisted deposition readily deposits finely-dispersed co-catalyst particles and simultaneously generates photocatalytic hydrogen. Another added advantage is that the photo-assisted deposition of the co-catalyst does not compromise the crystal structure or the integrity of the host photocatalyst, hence offering a better alternative to the doping technique. A systematic study of various transition metal chalcogenide co-catalysts and optimization of wt% MoS2, CuS and Ag2S loadings were demonstrated. Among them, the ZnIn2S4/MoS2 composite exhibits exceptional photocatalytic hydrogen production and stability as well as superior MO degradation under visible light irradiation. The present methodology is expected to be extendable to various transition metal oxides/chalcogenides since ionic derivatives exhibit high affinity to a variety of materials under photoirradiation.