Microfluidics is the branch of science that deals with the behavior of fluids through microchannels. It also deals with the technology of manufacturing miniaturized devices containing chambers and tunnels through which fluids can flow or remain confined. These devices work with very small volumes of fluids, down to 1 cc or so. 

Fluids behave very differently on the micrometric scale than in bulk quantities. The unique features and behaviors of tiny volumes of fluids absorbed into microchannels play unique detection and diagnostic roles in new scientific experiments and various emerging devices. Textiles rapidly emerge as the cheapest and most versatile components of microfluidic devices.

Polymers are widely used to fabricate microfluidic devices. Both thermoplastics and thermosets have found extensive use. Their preference is because they are robust, inexpensive, and stable under strong biochemical environments. The availability of a wide range of polymeric materials and the possibility of modifying their properties through chemical and thermal means are other factors that govern their popularity. 

Hydrophilic multifilament threads can transport aqueous and non-aqueous fluids via capillary action and possess desirable properties for building fluid transport pathways in microfluidic devices. In recent years, low-cost microfluidic devices based on mono and multifilament threads and fabricated textiles have found important applications in disease detection, diagnosis, and environmental mitigation. 

These devices are usually integrated with one or more analysis techniques, such as electrochemical, colorimetric, electrophoretic, chromatographic, and fluorescence techniques. The combination allowed the construction of fully portable devices suitable for point-of-care and wearable applications.

A combination of hydrophilic and hydrophobic threads can fabricate precisely controlled low-cost fabric patterns that will serve as inexpensive microfluidic devices. Threads can also be used to manufacture fabrics that can be patterned to achieve suitable hydrophilic-hydrophobic control. Recent research on textile microfluidic devices focused on modeling the fluid flow in the microfluidic thread and textile-based systems. The work also focused on thread surface treatments and the potential of combining multifilament threads with other materials to construct devices with expanded functionality. 

Fabric-based two-dimensional (2D) and three-dimensional (3D) microfluidic devices fabricated using organic cotton and wax have demonstrated how instant absorption of tiny volumes of colored fluids in preferred locations can be accomplished. These devices are suitable for colorimetric protocols whose sensing principle is based on color change. Anhydrous sodium bicarbonate (NaHCO3) was used to remove the natural wax from preferred locations of the fabric to make these locations hydrophilic in nature. 

It was shown that side-by-side hydrophilic-hydrophobic zones down to 1mm in size could be created in ordinary cotton fabric by removing natural wax and applying wax to cotton in preferred patterns. The material containing tiny jones that can either attract or repel fluids can be used to detect the presence or absence of fluids, including contaminated and differently colored fluids.

Water pollution is a major problem today, causing a shortage of freshwater around the globe. Heavy metals, pharmaceutical waste materials, and organic and inorganic contaminants in water bodies pose significant threats to the environment and public health. Currently available monitoring techniques involve complex equipment, longer processing time, and highly skilled professionals, making these techniques expensive and inaccessible. Towards achieving a portable, highly sensitive, and selective water quality control system, microfluidic devices have emerged as the preferred choice. 

Several researchers have turned their attention to microfluidic devices and are focusing on developing appropriate devices to detect contaminants in water. 

Polymer and textile-based microfluidic devices are expected to play a big role in detecting and removing the pollutants in global water bodies.

This article was contributed by our expert Dr. Radhakrishnaiah Parachuru

Frequently Asked Questions Answered by Dr. Radhakrishnaiah Parachuru

Q1. What are the main advantages of using textile microfluidic devices?

They are the least expensive, costing only cents as opposed to 10s and 100s of dollars. Their low cost is due to inexpensive materials and low fabrication costs. They are very tiny in size and durable.

Q2. What is the future of textile microfluidics devices?

They are expected to play a major role in disease detection and diagnosis. They are also likely to play a major role in detecting and remediating water and environmental pollution.

Q3. What are the applications of microfluidic devices?

Remote detection of diseases and harmful materials; protection of natural resources and the environment.

Q4. What are microfluidic manufacturing techniques?

Controlled extrusion of fibers and filaments; 3D Printing and additive manufacturing. Textile fabrication techniques include weaving and nonwoven production, photolithography, micro-transfer molding, thermoforming, injection molding, and laser ablation.