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Microfabrication
The chip design is shown in Figure 3. The fluidic layer of the dispensing device was produced

via soft lithography from 3D-printed molds manufactured using stereolithography from Accura
Xtreme (Shapeways, US). PDMS (Sylgard 184, DowSil) was mixed with the cross-linking

agent at a ratio of 10:1, the mixture was spun down for 5 minutes and then degassed in a vacuum

chamber for 15 minutes. Molds were filled with PDMS mixture and degassed to remove air
prior to overnight curing at 70° C. The deflective membrane and the pneumatic layer were

produced via xurography 16 . Silicone sheets of 0.25 and 0.5 mm (HT-6240, Rogers
Corporation) were cut using a knife plotter (GS‑24, Roland DGA). As interface layer, access

holes of 1 mm in diameter were drilled into glass slides and cleaned in 70 % ethanol in an
ultrasound bath for 15 minutes at RT before accommodating of the pneumatic tubing. The

layers were bonded by placing two sequential layers into a plasma-bonding chamber (Basic

Plasma Cleaner, PDC-32G-2, Harrick-Plasma, USA) for 2 minutes at the highest power setting.
The two layers were carefully aligned on top of each other, pressed together for 5 minutes and

then cured in the oven at 70° C for at least one hour, before adding the next layer. Once all the

layers were assembled, the device was placed at 70° C overnight for a final bake to increase
bonding strength between the two types of silicone used for production. Finally, 1 cm long

pneumatic tubing was fixed on the interface using 2-component epoxy glue (LOCTITE EA
9492) cured at 70° C for 4 hours to ensure air-pressure-driven actuation of the on-chip valves.

Fabrication of microscaffolds
The microscaffolds were fabricated using a high-resolution 3D printing method of two-photon

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polymerization (2PP), as previously described . Zirconium sol-gel (ZrHyb) was used as
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described previously . In brief, 0.5 % w/w of 4,4′-Bis(diethylamino)benzophenone (160326,
Sigma-Aldrich) was dissolved as a photoinitiator in the zirconium sol-gel containing 1-

propanol as a solvent. The microscaffolds were produced using the following settings: laser
-1
power of 140 mW, scanning speed of 1000 mm s , a hatch distance dX/dY of 0.5 µm and a
layer spacing dZ of 2.5 µm. After structuring with 2PP, the sample holder was submerged in
1-propanol for 1 h to dissolve any uncrosslinked material. Two additional washing steps were

carried out before storing the microscaffolds in 1-propanol.

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