A glucose-responsive hydrogel that changes its volume when exposed to different glucose concentrations was used to measure the glucose levels under physiological conditions.

Measuring pH has become a major key for determining health conditions, and food safety. The traditional pH assessment approaches are costly and offer low sensitivity. Here, a novel pH sensor based on a pH-responsive hydrogel has been developed. A Fresnel lens pattern was replicated on the surface of the pH-responsive hydrogel using the replica mould method. The pH sensors were tested in a pH range of 4–7. Introducing various pH solutions to the pH sensor led to volumetric shifts as the hydrogel swelled with pH. Consequently, the dimensions of the replicated Fresnel lens changed, modifying the focal length and the focus efficiency of the optical sensor. As a result, the measured optical power at a fixed distance from the sensor changed with pH. The optical sensor showed the best performance in the acidic region when pH changed from 4.5 to 5.5, in which the recorded power increased by 13%. The sensor exhibited high sensitivity to pH changes with a short respond time in a reversible manner. The developed pH optical sensor may have applications in medical point-of-care diagnostics and wearable continuous pH detection devices.

The joining of aluminium (Al) and copper (Cu) is an essential spot weld for renewable energy applications due to its excellent thermal and electrical conductivity. It is challenging to produce a high-quality Al-Cu spot weld using traditional techniques and the durability of a weldment is also uncertain. A new welding technique that is effective and suitable for spot welding Cu and Al is friction-melt-bonding (FMB) spot welding. The process parameters employed during welding have a strong impact on the quality of a weld. The strategy for integrating the FMB process characteristics, such as tool rotational speed and dwell time, into a mathematical model that may be used for predicting the process parameters of dissimilar spot joints, was the focus of this study. The findings showed that the tensile shear fracture load (TSFL) was significantly influenced by the tool's rotational speed and dwell time. Optimization was carried out using the response surface methodology (RSM) to find the best FMB process parameters for making a dissimilar spot weld of AA 6061-Cu.

Glaucoma is a major cause of irreversible blindness worldwide. The most acknowledged biomarker to diagnose and monitor glaucoma progression is intraocular pressure (IOP). Gold standard techniques for IOP monitoring are invasive, uncomfortable, and require visiting a clinic. In addition, most methods only provide a single snapshot on widely varying parameters. On the other hand, contact lenses have attracted particular interest to be used as continuous monitoring platforms to incorporate sensors, drugs, and more. Here, commercial contact lenses were laser-processed to be capable of detecting IOP variations in the physiological range. Three ring-couples with interspaces of 1.0, 1.5, and 2.0 mm were engraved on three soft contact lenses separately by using a carbon dioxide laser. The IOP/pressure variations induced repeatable changes in the ring-couple interspace which acted as a smartphone-readable pressure sensor. The processed contact lenses may be a potential candidate toward IOP monitoring at point-of-care settings.

The authors report on the laser-induced modification of surface properties of contact lenses. Selective areas of the surface of commercial silicon-hydrogel contact lenses are patterned in array formats using different powers of the CO 2 laser. 1D arrays of different groove densities, channels, and 2D intersecting architecture are fabricated. Contact angle measurements are carried out to measure the surface hydrophilicity, and extent of hydration is linked with the surface profile properties and the space gap between the fabricated patterns, which are controlled by the beam exposure time, beam power, and scan speed. Laser treatment of contact lenses results in improved hydration proportional to the density of laser ablated segments on the surface. The hydration time of water droplets on different lens surfaces is also recordedall 2D patterned lenses show faster hydration as water quickly diffused into the bulk of the lens due to the extended interfacial area between the contact lens and the water droplet as a consequence of larger areal modification in 2D as compared with 1D patterns. The best wettability properties are obtained with 0.3 mm space gap, 9 W power, and 200 mm s À1 scan speed. Optical microscopy is used to image the 3D surface profiles of the modified lenses and the depth of the patterns and is correlated with the experimental observations. The maximum depth of 40 mm is observed with 0.3 mm space gap, 9 W, and 200 mm s À1 scan speed. Optical transmittance of broadband white light is measured to assess the surface treatment effects on the contact lenses. A large exposure and dense patterning of contact lens result in decreased (down to a minimum of 45%) in the light transmittance, which dictates the practical usability of such patterning. Surface treatment of contact lenses can be utilized to deposit stable conducting connection for onlens-LEDs, displays, and communication antennas as well as for stabilizing biosensing materials and drug dispensing applications.