20
D. K. Subbiah et al.
solution and the generated droplets will be sprayed over the surface of substrate that
maintaining at certain temperature [96].
The sprayed droplets will undergo for an evaporation of solvents before reaching
the surface of substrate. Then, the remaining residues will get impinge where further
decomposition occurs and leads to deposition of desired compound as particles or
thin films. The reactants in a precursor solution for spray pyrolysis are selected on
the basis that other than desired compound, remaining products should be volatile
at the temperature of deposition [97]. The substrate temperature is one of the main
factors in determining the nucleation sites, which contributes to the morphology of the
film. Apart from substrate temperature, the quality, properties, thickness of desired
thin film over substrate will also be dictated by some other parameters start from
anion-cation ratio in precursor, spray rate, distance between spray nozzle-substrate,
droplet size and solvent evaporation rate. Hence, optimization of all these components
enables to form a desired film for wide range of potential applications [98].
In transformation era of rigid (glass thin film) to flexible (cotton textile) device,
spray pyrolysis still withstands in a row of surface modification techniques due to its
versatility. In recent studies, significant number of research articles were published
on surface modification of textiles by spray pyrolysis to various applications like
photocatalytic [99], antimicrobial [100] and flame retardancy [101]. The principle
and mechanism of deposition on cotton textile substrate are all same like deposition
on glass substrate. It is noted to be that substrate temperature is an important concern. The given substrate temperature should not affect the nature of the substrate;
withstand temperature of cotton textile is comparatively lower compared to glass
substrate.
3.3.4 Pad-Dry-Cure Method
Pad-Dry technique is a well-known commercial technique to modify the surface of
the textiles/cotton fabrics. In process, textile is passed (i.e. dipped) to the solution
containing the active materials to be deposited followed by drying/curing using heat
or pressure. The number of dipping cycles may increase or decrease that depends on
need of material finishing towards end applications like anti-bacterial, water proofing, softening, etc. It offers low-cost, continuous and large-scale production of surface modified textiles for wearable applications. Karim et al. reported the scalable
production of graphene modified textile using pad-dry technique for human activity monitoring application where change in resistance is calculated with respect
to bending actions [25]. Initially, GO was synthesized using modified Hummers
method and chemically reduced to rGO using the reducing agent, sodium hydrosulphite (Na 2 S 2 O 4 ). Dispersed rGO solution was then taken into the pad-dry unit where
the unmodified fabric was passed through the padding bath containing rGO. The rGO
coated fabric was then dried at 100 °C for 5 min to ensure the graphene deposition on
the fabric surfaces. From the results, it was shown that rGO was uniformly deposited
on the surface of textile and provided good electrical conductivity [25].
D. K. Subbiah et al.
solution and the generated droplets will be sprayed over the surface of substrate that
maintaining at certain temperature [96].
The sprayed droplets will undergo for an evaporation of solvents before reaching
the surface of substrate. Then, the remaining residues will get impinge where further
decomposition occurs and leads to deposition of desired compound as particles or
thin films. The reactants in a precursor solution for spray pyrolysis are selected on
the basis that other than desired compound, remaining products should be volatile
at the temperature of deposition [97]. The substrate temperature is one of the main
factors in determining the nucleation sites, which contributes to the morphology of the
film. Apart from substrate temperature, the quality, properties, thickness of desired
thin film over substrate will also be dictated by some other parameters start from
anion-cation ratio in precursor, spray rate, distance between spray nozzle-substrate,
droplet size and solvent evaporation rate. Hence, optimization of all these components
enables to form a desired film for wide range of potential applications [98].
In transformation era of rigid (glass thin film) to flexible (cotton textile) device,
spray pyrolysis still withstands in a row of surface modification techniques due to its
versatility. In recent studies, significant number of research articles were published
on surface modification of textiles by spray pyrolysis to various applications like
photocatalytic [99], antimicrobial [100] and flame retardancy [101]. The principle
and mechanism of deposition on cotton textile substrate are all same like deposition
on glass substrate. It is noted to be that substrate temperature is an important concern. The given substrate temperature should not affect the nature of the substrate;
withstand temperature of cotton textile is comparatively lower compared to glass
substrate.
3.3.4 Pad-Dry-Cure Method
Pad-Dry technique is a well-known commercial technique to modify the surface of
the textiles/cotton fabrics. In process, textile is passed (i.e. dipped) to the solution
containing the active materials to be deposited followed by drying/curing using heat
or pressure. The number of dipping cycles may increase or decrease that depends on
need of material finishing towards end applications like anti-bacterial, water proofing, softening, etc. It offers low-cost, continuous and large-scale production of surface modified textiles for wearable applications. Karim et al. reported the scalable
production of graphene modified textile using pad-dry technique for human activity monitoring application where change in resistance is calculated with respect
to bending actions [25]. Initially, GO was synthesized using modified Hummers
method and chemically reduced to rGO using the reducing agent, sodium hydrosulphite (Na 2 S 2 O 4 ). Dispersed rGO solution was then taken into the pad-dry unit where
the unmodified fabric was passed through the padding bath containing rGO. The rGO
coated fabric was then dried at 100 °C for 5 min to ensure the graphene deposition on
the fabric surfaces. From the results, it was shown that rGO was uniformly deposited
on the surface of textile and provided good electrical conductivity [25].