The development of accurate and rapid techniques to produce nanophotonic structures is essential in data storage, sensors, and spectroscopy.
Gold is a standard surface for attachment of thiol-based self-assembled monolayers (SAMs). To achieve uniform defect free SAM coatings, which are essential for bio/chemical sensing applications, the gold surface must have low roughness, and be highly orientated. These requirements are normally achieved by either heating during Au deposition or post deposition Au surface annealing. This paper shows that room temperature deposited gold, can afford equivalent gold surfaces, if the gold deposition parameters are carefully controlled. This observation is an important result as heating (or annealing) of the deposited gold can have a detrimental effect on the mechanical properties of the silicon on which the gold is deposited used in microsensors. The paper presents the investigation of the morphology and crystalline structure of Au film prepared by thermal evaporation at room temperature on silicon. The effect of gold deposition rate is studied, and it is shown that by increasing the deposition rate from 0.02 nm s -1 to 0.14 nm s -1 the gold surface RMS roughness decreases, whereas the grain size of the deposited gold is seen to follow a step function decreasing suddenly between 0.06 and 0.10 nm s -1 . The XRD intensity of the preferentially [111] orientated gold crystallites is also seen to increase as the deposition rate increases up to a deposition rate of 0.14 nm s -1 . Formation and characterization of 1-dodecanethiol on these Au coated samples is also studied using contact angle. It is shown that by increasing the Au deposition rate the contact angle hysteresis (CAH) decreases until it plateaus, for a deposition rate greater than 0.14 nm s -1 , where the CAH is smaller than 9 degrees which is an indication of homogeneous SAM formation, on a smooth surface. 2
The intraocular pressure (IOP) is a physiological parameter that plays a crucial role in preventing, diagnosing, and treating ocular diseases. For example, lowering the IOP is the primary focus of glaucoma management. However, IOP is a widely varying parameter, and one-off measurements are prompt to errors. Developing portable solutions for continuous monitoring the IOP is a critical goal in ophthalmology. Here, stretchable nanostructures were developed as strain-tunable diffraction gratings and integrated into a contact lens. They exhibited a limit of detection (LOD) <2 mmHg and a linear response in the range of interest (15−35 mmHg). Nanopatterns were characterized under monochromatic laser sources and further integrated into a soft contact lens. A smartphone readout method based on preferentially reflected colors was proposed to pave the way toward smartphone-based ocular health monitoring.
Although plasma treatment can alter polymer surface wettability and adhesiveness, scant attention has been given to plasma effects across scales and their anti‐fouling performance. Herein, the discovery that plasma‐activated polydimethylsiloxane (PDMS) nanopillar arrays remarkably enhance anti‐fouling behavior, yielding a 98.7% reduction in Escherichia coli adhesion compared to native planar surfaces. The plasma‐activated nanopillar arrays can hold to their anti‐fouling properties for extended periods of storage, still exhibiting more than 65.1% less bacterial colonization than their native planar counterparts after 50 days. The anti‐fouling behavior promoted by plasma activation is significantly enhanced as the structure features reduce in size from macroscale to microscale to nanoscale, revealing an altered plasma activation effect upon confinement at the nanoscale level. It is anticipated that the findings will improve the ability to achieve non‐fouling effects in polymeric materials for a broad range of applications in clinical and industrial settings.
The reference cantilever method is shown to act as a direct and simple method for determination of torsional spring constant. It has been applied to the characterization of micropaddle structures similar to those proposed for resonant functionalized chemical sensors and resonant thermal detectors. It is shown that this method can be used as an effective procedure to characterize a key parameter of these devices and would be applicable to characterization of other similar MEMS/NEMS devices such as micromirrors. In this study, two sets of micropaddles are manufactured (beams at centre and offset by 2.5 μm) by using LPCVD silicon nitride as a substrate. The patterning is made by direct milling using focused ion beam. The torsional spring constant is achieved through micromechanical analysis via atomic force microscopy. To obtain the gradient of force curve, the area of the micropaddle is scanned and the behaviour of each pixel is investigated through an automated developed code. The experimental results are in a good agreement with theoretical results.
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