Photonic hydrogel sensors

Alqurashi, Yousef (2020). Photonic hydrogel sensors. University of Birmingham. Ph.D.

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Abstract

Hydrogels are an important tools for sensing because of their sensitivity to small adjustments and reactions to physical, biological, and chemical changes. They have been used in wide range of applications such as biomedical fields for drug delivery and in diagnostics. Hydrogel-based systems are a reusable sensing platform to quantify biomarkers in high-risk patients at clinical and point-of-care settings. In this thesis, two fabrication methods have been developed to successfully detect glucose concentration, pH changes and intraocular pressure (IOP). Continuous glucose monitoring aims to achieve accurate control of blood glucose concentration to prevent hypo/hyperglycaemia in diabetic patients. Also, the development of pH changes sensing device is the key to prevent the fatal implications. The Increasing of intraocular pressure (IOP) is the main risk factor for glaucoma, which is the second major source of losing sight in the world.

The first method is to developed hydrogel-based sensor by using stamping technique. A novel glucose sensor based on hydrogel with a micro-imprinted hexagonal structure was fabricated here. Our method utilized diffraction properties of a hexagonally photonic microscale concavities to detect the changes in the glucose concentration from 1 mM to 200 mM. In addition, same method was used to design a new pH hydrogel-based sensor with imprinted Fresnel lens. The sensor was able to monitor the pH changes with respond time of 5 minutes. The sensor had pH range from 4.5 to 7 and showed an increase in the sensitivity after 10 days storage in PBS solution of pH 7.4. Also, when the effect of temperature changes was investigated in the study, the temperature effect was negligible in the performance the sensor.

The second method is Laser ablation of commercial contact lenses. Initially, CO2 laser (HPC LS 3040) was used to modify the surface properties of the lens at selective areas by creating 1D and 2D patterns. Laser parameters (space gap between the patterns and laser power, and scan speed) were examined to find the optimal laser setting. We managed to improve the wettability properties of the lens by increasing the density of the surface. After that, we engraved two circular micro-channels on the contact lens using CO2 laser (Rayjet laser). Three different lenses were fabricated with various spacing gap between the channels (1 mm, 1.5 mm and 2 mm). The lenses had maximum channel depth of up to 20 µm. By using laser treated lenses, a change in pressure from 12 mmHg to 22 mmHg, normal eye IOP and glaucoma patients IOP, was detect by the lenses.

In summary, this thesis presents important findings that can be recommended for application in medical point-of-care diagnostics, implantable chips, and wearable continuous monitoring devices to quantify biomarkers. These methods offer sensing devices that are easy and fast to manufacture, cost effective, fast response and noninvasive sensors.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):