addition, the nanowires (Fig.4.7a, 1), metal interconnects (Fig.4.7a, 2), and SU-8
structural elements (Fig.4.7a, 3) had an areal mass density of <60μg/cm^2 , the
lowest value reported so far forflexible electronics, which reflects our macroporous
architecture. The mesh nanoES wasflexible and can be manually rolled into tubular
constructs with inner diameters at least as small as 1.5 mm (Fig.4.7b), and folded.
Macroporous structures of the open mesh nanoES were formed either by loosely
stacking adjacent mesh layers (Fig.4.7c) or by shaping it with other biomaterials.
These capabilities were consistent with the estimated ultralow effective bending
stiffness, which was tuned between 0.006 and 1.3 nN m for this mesh and is
comparable to recent planar epidermal electronics [ 17 ].
We evaluated the electrical transport characteristics of the mesh nanoES in PBS.
Yield (90–97%), average conductance ( 3 μS) and sensitivity ( 7 μS/V)
(Fig.4.8a) of mesh electronics are comparable to planar nanowire FET device [ 18 ].
Representative conductance (G) data (Fig.4.8b) from single nanowire FET
(Fig.4.8b, yellow dots, upper panel) during the rolling process showed a <0.17μS
conductance change (DG) or <2.3% total change for 6 revolutions. Device sensi-
tivity (S) remained stable with a maximum change (DS) of 0.031μS/V, or 1.5%
variation. Furthermore, 14 devices evenly distributed on 6 layers of a rolled-up
scaffold (Fig.4.8c) showed maximum differences ofDG = 6.8 andDS = 6.9%
versus the unrolled state, demonstrating device robustness. Repetitive rolling and
relaxation to theflat state did not degrade nanowire FET performance. These
findings suggest potential for reliable sensing/recording of dynamic and deformable
systems.
Fig. 4.8 Device performance characterization.aHistograms of nanowire FET conductance and
sensitivity in one typical mesh nanoES.bWater-gate sensitivity and conductance of a nanowire
FET device in a mesh device during the rolling process. Upper panel, schematic of nanowire FET
position (yellow dot) during rolling process; 0–6 denote the number of turns.cRelative change in
conductance and sensitivity of 14 nanowire FETs evenly distributed throughout a fully rolled-up
mesh device. Upper panel, schematic of nanowire FET position (yellow dots). Inbandcthe
thicknesses of the tubular structures have been exaggerated for schematic clarity
4.3 Results and Discussion 49