350-nm thick SU-8 layers. For the ribbons without metal contact lines, the total
SU-8 thickness is ca. 700 nm. Transverse ribbons and longitudinal ribbons together
form mesh with periodic unit cells. The dimensions of all unit cells are identical
across the whole mesh. Design #1 is used for injection by needle with inner
diameter larger than 200μm. The width of mesh is 5–15 mm. The length of unit
cell is 333μm and width of unit cell is 250μm. All the SU-8 layers are 20μmin
width and all the metal layers are 10μm in width. Design #2 is used for injection by
needle with inner diameter smaller than 200μm. The width of mesh is 2–5mm.
The length of unit cell is 333μm and width of unit cell is 250μm. SU-8 layers in
longitudinal ribbons are 20μm in width and SU-8 layers in transverse ribbons are
5 – 10 μm in width. Metal layers in longitudinal ribbons are 10μm in width and
metal layers in transverse ribbons are 2– 5 μm in width.
Control mesh electronics sample: The transverse ribbons are perpendicular to
the longitudinal ribbons witha=0ºto form an orthogonal mesh with the same
periodic unit cell structure. All metal line patterns, thickness and width of ribbons
are the same as design #1 of tilted transverse ribbons electronics. The width of
electronics is 5–15 mm for testing.
Control thinfilm electronics sample: The thickness of SU-8 is 700 nm. All the
metal line patterns are the same as design #1 of tilted mesh electronics. The width of
electronics is 0.1–5mm.
5.2.3 Injection of Mesh Electronics......................
Surface modification of electronics for syringe injectable: The freestanding
electronics was transferred into DI water by glass pipette to remove nickel etchant or
developer solution. Then the electronics was transferred and soaked into
Fig. 5.2 Schematics of mesh
design. Schematics show the
structures of 2 different mesh
designs. Black dashed boxes
highlight the unit cell
structure. Red, supporting and
passivation polymer and
yellow, metal lines
68 5 Syringe Injectable Electronics