recorded using Clampex 10 software. The nanowire FET conductance and
transconductance (sensitivity) were measured and calculated in 1PBS as
described previously [ 10 ].
2.3 Results and Discussion
2.3.1 3D Macroporous Nanoelectronic Network
We combine both“bottom-up”and mechanics-driven approaches to realize 3D
macroporous nanoelectronic networks (Fig.2.3). In this approach, we utilize
functional nanowires as nanoelectronic elements (Fig.2.3a). The variations of
nanowires in composition, morphology and doping encoded during synthesis [ 11 –
19 ]define diverse functionality including devices for logic and memory [ 20 , 21 ],
sensors [ 18 , 23 ], light-emitting diodes [ 17 ], and energy production and storage [ 24 ,
25 ]. Through a combination of nanowire assembly and conventional 2D lithogra-
phy carried out on a sacrificial substrate (see below), we canfirst realize 2D mesh
nanoelectronic networks with multiple functions. Then, we remove the sacrificial
layer to yield a free-standing andflexible 2D mesh nanoelectronic network as
precursor for 3D macroporous electronics (Fig.2.3b). Third, we implemented
internal stress into the metal interconnects of 2D mesh electronic network during
fabrication. This stress, due to its designed distribution, creates forces to organize
the freestanding 2D mesh nanoelectronic precursor into a regular 3D macroporous
structure.
The key steps for this“bottom-up”fabrication process are outlined in Fig.2.4.
First, nanowires were uniaxially-aligned by contact printing [ 14 ] on the surface of a
layer of SU-8 negative resist (Fig.2.4a, I). Second, the SU-8 layer with aligned
nanowires was patterned to define a periodic array by lithography, and the excess
nanowires on unexposed regions of the SU-8 were removed when the pattern was
developed (Fig.2.4a, II). The nanowire density and feature size in periodic arrays
Fig. 2.3 Strategy for preparing 3D macroporous nanoelectronic networks.aDifferent nanowire
nanoelectronic elements such as kinked nanowire, nanotube, core-shell, straight and branched
nanowire.bFreestanding 2D macroporous nanowire nanoelectronic“precursor”. Blue: nanoelec-
tronic element, orange: passivation polymer, black: metal contact and input/output (I/O)
2.2 Experimental 19