In the contemporary world, wearable electronics and smart
textiles/fabrics
are galvanizing a transformation of the health care, aerospace, military,
and commercial industries. However, a major challenge that exists
is the manufacture of electronic circuits directly on fabrics. In
this work, we addressed the issue by developing a sequential manufacturing
process. First, the target fabric was coated with a customized ink
containing lignin. Next, a desired circuit layout was patterned by
laser burning lignin, converting it to carbon and establishing a conductive
template on the fabric. At last, using an in-house-designed printer,
a devised localized hydrogen evolution-assisted (HEA) copper electroplating
method was applied to metalize the surface of the laser-burned lignin
pattern to achieve a very low resistive circuit layout (0.103 Ω
for a 1 cm long interconnect). The nanostructure and material composition
of the different layers were investigated via scanning electron microscopy,
energy-dispersive X-ray spectroscopy (EDX), Raman spectroscopy, and
Fourier-transform infrared spectroscopy (FTIR). Monitoring the conductivity
change before and after bending, rolling, stretching, washing, and
adhesion tests presented remarkable mechanical stability due to the
entanglement of the copper nanostructure to the fibers of the fabric.
Furthermore, the HEA method was used to solder a light-emitting diode
to a patterned circuit on the fabric by growing copper at the terminals,
creating interconnects. The presented sequential printing method has
the potential for fabricating reliable wearable electronics for various
applications, particularly in medical monitoring.