Electronic textiles, which are a
combination of fabrics and electronics,
can help realize wearable electronic devices by changing the rigidity
of these textiles. We demonstrate organic light-emitting diodes (OLEDs)
by directly printing the emitting material on fabric substrates using
the nozzle-printing technique. Printing the emitting material directly
on a fabric substrate with a rough surface is difficult. To address
this, we introduce a planarization layer by using a synthesized 3.5
wt % poly(vinyl alcohol) (PVA) solution. The sputtered ITO anode with
the thermally annealed PVA planarization layer on a fabric substrate
achieves a low sheet resistance in the range of 60–80 Ω/sq,
whereas the ITO electrode without a PVA layer exhibits high sheet
resistance values of 10–25 kΩ/sq. This result is because
the thermally annealed PVA layer on the fabric surface has a uniform
surface morphology and a water contact angle as high as 96°,
thus acting as a protective layer with a waterproofing effect; in
contrast, the water is completely absorbed on the rough surface without
a PVA layer. The fabric-based OLEDs with a thermally annealed PVA
layer exhibit a lower turn-on voltage of 3 V and higher luminance
values of 5346 cd/m2 at 8 V compared with the devices without
a PVA layer (7 V and 3622 cd/m2) at 18 V. These fabric-based
OLEDs with a PVA planarization layer can be produced by the nozzle-printing
process and can achieve selective patterning as well as direct printing
of the emitting material and ITO sputtering on a fabric substrate;
furthermore, they emit well even when it bent into a circle with a
radius of 1 cm.
In the present study, the surface of non-woven polypropylene (NW-PP) fabric was modified to form CN layers using a modified DC-pulsed (frequency: 60 kHz, pulse shape: square) sputtering with a roll-to-roll system. After plasma modification, structural damage in the NW-PP fabric was not observed, and the C–C/C–H bonds on the surface of the NW-PP fabric converted into C–C/C–H, C–N(CN), and C=O bonds. The CN-formed NW-PP fabrics showed strong hydrophobicity for H2O (polar liquid) and full-wetting characteristics for CH2I2 (non-polar liquid). In addition, the CN-formed NW-PP exhibited an enhanced antibacterial characteristic compared to NW-PP fabric. The reduction rate of the CN-formed NW-PP fabric was 89.0% and 91.6% for Staphylococcus aureus (ATCC 6538, Gram-positive) and Klebsiella pneumoniae (ATCC4352, Gram-negative), respectively. It was confirmed that the CN layer showed antibacterial characteristics against both Gram-positive and Gram-negative bacteria. The reason for the antibacterial effect of CN-formed NW-PP fabrics can be explained as the strong hydrophobicity due to the CH3 bond of the fabric, enhanced wetting property due to CN bonds, and antibacterial activity due to C=O bonds. Our study presents a one-step, damage-free, mass-productive, and eco-friendly method that can be applied to most weak substrates, allowing the mass production of antibacterial fabrics.
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