injected solution less than 100 nL in each injection to minimize the invasiveness
(Fig.5.8). Injected mesh electronics can gradually unfold in the aqueous solution
due to the reduction of surface energy and release of the internal strain. This
precisely controlled injection process allows us to inject mesh electronics with
sensors into the targeted system while eject the metal interconnects and I/O region
on the outside. We further use the anisotropic conductivefilm (ACF) to bond the I/
O pads of mesh electronics with external recording set-ups (Fig.5.4).
We evaluate the correlation between the yields of device after injection to the
inner diameter (ID) of needle by using standard metal gauge needles (Fig.5.9). The
average yield of mesh electronics containing semiconductor nanowires ranges from
98% (600μm, ID) to 83% (100μm, ID) with less than 12% conductance change in
average. The average yield of injection for metal electrode ranges from 90%
Fig. 5.8 Control of injection process.aOptical images of a typical device during injection
process. (I–VI) The device is gradually injected into free solution by micro-injector with 1 bar
pressure, 10 ms pulse (before blue dashed line inband 50 ms pulse (after blue dashed line in (b))
injection time for each step.bThe injected length of device versus number of injection. Blue arrow
(I–III) corresponding to images (I–III) in (a). Blue arrow (IV–VI) corresponding to images (IV–
VI) in (a)
80 5 Syringe Injectable Electronics