Researchers test a self-hydrating contact lens

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Publishing in the journal Additive Manufacturing, a team of researchers from the Manipal Institute of Higher Education in India report the development of a 3D printed self-wetting contact lens.Currently in the pre-validation stage, the research has important implications for the development of next-generation contact lens-based medical devices.

Smart Contact Lenses

Smart Contact Lenses
Study: Self-Wetting Contact Lenses Using Capillary Flow.Image credit: Kichigin/Shutterstock.com
Contact lenses are often used to correct vision and have the advantage of being easier to wear than glasses.Additionally, they have cosmetic uses, as some people find them more aesthetically pleasing.In addition to this traditional use, contact lenses have been explored for applications in biomedicine to develop non-invasive smart sensing devices and point-of-care diagnostics.
Several studies have been carried out in this area and some noteworthy innovations have been developed.For example, Google lens is a smart contact lens that can be used to monitor glucose levels in tears and provide diagnostic information for people with diabetes.Intraocular pressure and eye movements can be monitored using smart devices.Nanostructured materials have been incorporated into smart contact lens-based sensing platforms to act as sensors.
However, the use of these devices can be challenging, hindering the commercial development of contact lens-based platforms.Wearing contact lenses for extended periods of time can cause discomfort, and they tend to dry out, causing more problems for the wearer.Contact lenses interfere with the natural blinking process, resulting in insufficient water retention and damage to the delicate tissue of the human eye.
Traditional methods include eye drops and punctal plugs, which improve tear stimulation to hydrate the eyes.Two novel approaches have been developed in recent years.
In the first approach, single-layer graphene is used to reduce water evaporation, although this approach is hampered by complex fabrication methods.In the second method, electroosmotic flow is used to keep the lens hydrated, although this method requires the development of reliable biocompatible batteries.
Contact lenses are traditionally manufactured using lathe machining, forming and spin casting methods.Molding and spin-casting processes have cost-effective advantages, but they are hampered by complex post-processing treatments to improve material adhesion to the mold surface.Lathe fabrication is a complex and expensive process with design constraints.
Additive manufacturing has emerged as a promising alternative to traditional contact lens manufacturing techniques.These techniques offer benefits such as reduced time, greater design freedom, and cost-effectiveness.3D printing of contact lenses and optical devices is still in its infancy, and research on these processes is lacking.Challenges arise with loss of structural features and weak interfacial adhesion in post-processing.Decreasing the step size results in a smoother structure, which improves adhesion.
Although more and more research has focused on the use of 3D printing methods to make contact lenses, there is a lack of discussion about making molds compared to the lenses themselves.Combining 3D printing technology with traditional manufacturing methods offers the best of both worlds.
The authors used a novel method to 3D print self-wetting contact lenses.The main structure was fabricated using 3D printing, and the model was developed using AutoCAD and stereolithography, a common 3D printing technique.The diameter of the die is 15 mm and the base arc is 8.5 mm.The step size in the manufacturing process is only 10 µm, overcoming traditional problems with 3D printed contact lenses.

Smart Contact Lenses

Smart Contact Lenses
The optical areas of the manufactured contact lenses are smoothed after printing and replicated onto PDMS, a soft elastomeric material.The technique employed in this step is a soft lithography method.A key feature of printed contact lenses is the presence of curved microchannels within the structure, which gives them the ability to self-wet.Furthermore, the lens has good light transmission.
The authors found that the layer resolution of the structure dictated the dimensions of the microchannels, with longer channels printed in the middle of the lens and shorter lengths at the edges of the printed structures.However, when exposed to oxygen plasma, the structures became hydrophilic, facilitating capillary-driven fluid flow and wetting the printed structures.
Due to the lack of microchannel size and distribution control, microchannels with well-defined microchannels and reduced step effects were printed onto the master structure and then replicated onto the contact lens.Use acetone to polish the optical regions of the main structure and print curved capillaries to circumvent the loss of light transmission.
The authors say their new method not only improves the self-moisturizing ability of printed contact lenses, but also provides a platform for future development of lab-on-a-chip-enabled contact lenses.This opens the door for their use as functional real-time biomarker detection applications.Overall, this study provides an interesting research direction for the future of contact lens-based biomedical devices.


Post time: Apr-30-2022