5.3.4 Syringe-Injectable Electronics for Behaving Rodent
Brais
Based on our simulation,DL of mesh electronics that can be injected is ca.
0.01 nNm, which is similar to the bending stiffness of tissue. In addition, the
bending energy of mesh electronics matches the surface membrane energy [ 32 ]of
single cells and 1 million times less than the bending stiffness of the conventional
silicon probe and carbonfibers [ 24 , 27 ]. In addition, our previous studies [ 8 ] have
demonstrated that the design of these macroporous structures has allowed the
growth of tissue within interior spaces. Together, we consider syringe-injectable
electronics as a great candidate for in vivo chronic implants, especially for the soft
tissues such as brain.
We conducted the in vivo chronic implantation experiments by stereotactically
injecting mesh electronics into behaving rodent brain tissue with a 0.5-mm diameter
drilled hole from craniotomy. The injection follows steps illustrated in Fig.5.15a,
b. Specifically, 2-mm-wide electronics was injected into the tissue-dense hip-
pocampus region of the mice (Fig.5.15c, I) through a ca. 200-lm inner diameter
glass needle controlled by microinjector. This process only introduced trace amount
of solution (<1lL) into the brain showing vanishingly-small invasiveness.
Fluorescence imaging of coronal brain slice shows unfolding of mesh electronics
after 5 weeks in hippocampus region with little interruption to the layered structure
of neurons (Fig.5.15d, e). Immunostaining imaging further shows no proliferation
Fig. 5.14 Inject electronics for tissue engineering.aschematic of injection of electronics with
neuron cells into Matrigel. Red, SU8; Yellow, metal/SU8; Blue, nanodevices; Green, neuron cells.
bConfocalfluorescence images of 100 um projection show the interpenetration between neurons
and ribbons of injectable electronics after co-injected into matrigel for 14 days. Red: reflective
image of mesh and green: beta-tubulin staining for neurons
88 5 Syringe Injectable Electronics