posted on 2023-12-22, 16:03authored byKun Yu, Zhennan Qiu, Bingsong Gu, Jiaxin Li, Zijie Meng, Dichen Li, Jiankang He
Reliable insulation of microscale
conductive features
is required
to fabricate functional multilayer circuits or flexible electronics
for providing specific physical/chemical/electrical protection. However,
the existing strategies commonly rely on manual assembling processes
or multiple microfabrication processes, which is time-consuming and
a great challenge for the fabrication of flexible transparent electronics
with microscale features and ultrathin thickness. Here, we present
a novel coaxial electrohydrodynamic (CEHD) printing strategy for the
one-step fabrication of microscale flexible electronics with conductive
materials at the core and insulating material at the outer layer.
A finite element analysis (FEA) method is established to simulate
the CEHD printing process. The extrusion sequence of the conductive
and insulating materials during the CEHD printing process shows little
effect on the morphology of the core–shell filaments, which
can be achieved on different flexible substrates with a minimum conductive
line width of 32 ± 3.2 μm, a total thickness of 53.6 ±
4.8 μm, and a conductivity of 0.23 × 107 S/m.
The thin insulating layer can provide the inner conductive filament
enough protection in 3D, which endows the resultant microscale core–shell
electronics with good electrical stability when working in different
chemical solvent solutions or under large deformation conditions.
Moreover, the presented CEHD printing strategy offers a unique capability
to sequentially fabricate an insulating layer, core–shell conductive
pattern, and exposed electrodes by simply controlling the material
extrusion sequence. The resultant large-area transparent electronics
with two-layer core–shell patterns exhibit a high transmittance
of 98% and excellent electrothermal performance. The CEHD-printed
flexible microelectrode array is successfully used to record the electrical
signals of beating mouse hearts. It can also be used to fabricate
large-area flexible capacitive sensors to accurately measure the periodical
pressure force. We envision that the present CEHD printing strategy
can provide a promising tool to fabricate complex three-dimensional
electronics with microscale resolution, high flexibility, and multiple
functionalities.