Innovative hydrogel offers solutions for water desalination and biomedical applications

Researchers from the UPC's research group Innovation in Materials and Molecular Engineering - Biomaterials for Regenerative Therapies (IMEM-BRT) are working on a thermosensitive hydrogel with several applications, such as the desalination of seawater with solar radiation and the creation of new biomedical adhesives for semi-invasive therapies and for medical diagnosis.

An estimated 55 million people globally are affected by droughts every year, which could harm as many as three out of four people worldwide by 2050, according to the UN. This situation will worsen in the coming decades due to the lack of rainfall and the effects of climate change, causing serious environmental, economic and social damage. In this context, the development of low-cost technologies for the purification and desalination of seawater, using 100% organic materials and harnessing a natural resource like solar radiation, is crucial for meeting current and future demands for safe potable water in households.

To address this challenge, the TherGel project is being developed, led by Elaine Armelin and Joan Torras, researchers from the Innovation in Materials and Molecular Engineering - Biomaterials for Regenerative Therapies (IMEM-BRT) research group and professors at the Barcelona East School of Engineering (EEBE) of the Universitat Politècnica de Catalunya - BarcelonaTech (UPC).

The project focuses on developing a thermosensitive conductive hydrogel called solar absorber hydrogel (SAH). Thermosensitive hydrogels are polymeric materials capable of absorbing a large amount of water, depending on the temperature to which they are exposed, and expelling it free of salts and contaminants when heated above 32ºC. A conductive polymer is added, which acts as a photothermal absorber and enhances the water expulsion capacity, that is, the generation of potable water.

The result is a material that can be used in water filtration systems such as filtration membranes and capacitive deionization systems for saltwater. The aim is to develop a prototype for water self-purification to be used directly in homes, without the need for electrical sources or pressure equipment, as it would just use solar energy for the regeneration of saline water and the production of drinking water."

Elaine Armelin, Researcher

Researcher Joan Torras explains how this technology works: "As water is absorbed by the hydrogel, it rises to the surface and evaporates due to solar radiation. We add nanoparticles of a conductive polymer to this material, giving it a darker black colour, so it absorbs more solar radiation while favouring internal water evaporation. It is a small desalination unit to produce drinking water at home."

So far, the system has achieved an evaporation rate of around 3.5-4.5 kg/square meter per hour, which would account for about 80-100 kg/square meter of clean water in 24 hours. Preliminary results were published in the scientific journal Advanced Functional Materials.

The hydrogel could be manufactured at home with a preparation kit, since no industrial equipment is required, and it could be reused or recycled at home too. In addition, the electrical properties of the new conductive hydrogel make it potentially attractive in capacitive deionisation (CDI) cells as porous electrodes to increase the flow rate of purified water generation, considering that materials commonly used in industrial desalination equipment are expensive and very hard to recycle.

Biomedical materials modified with thermosensitive hydrogel

The property of thermosensitive hydrogels to retain liquids and respond to temperature changes makes them suitable for their application in medical implants, such as surgical meshes for repairing abdominal hernias, sponges for draining fistulas after surgical procedures and dressings for wounds, to name a few. This is the second challenge of the TherGel project.

The presence of the hydrogel in surgical meshes, for example, facilitates their adaptation to tissues due to the material's adhesion capacity and the possibility of detecting the implant through surface-enhanced Raman spectroscopy (SERS). As IMEM-BRT researcher Sonia Lanzalaco explains, "during implantation, the hydrogel is capable of self-opening to adapt to human body temperature, and once implanted it can provide information on temperature changes caused by a potential localised infection. Thanks to this hydrogel, the mesh could better adapt to organs, both in terms of flexibility and biocompatibility."

The researchers have applied biocompatible nanoparticles to the surgical mesh that have a theragnostic function, i.e. that combine therapy and diagnosis: they act as bactericides and at the same time they make it possible to detect the implant with less invasive spectroscopy tools, enabling more personalised therapies to meet each patient's needs. In addition, a self-adhesive mesh requires no staples, tacks or sutures, reducing inflammatory risks.

The three-year TherGel technological innovation project is financed by the Spanish State Research Agency (AEI) with a budget of 138.545 euros.