Microcontact printing of dendrimers, proteins, and nanoparticles by porous stamps

Porous stamps fabricated by one-step phase separation micromolding were used for microcontact printing of polar inks, in particular aqueous solutions of dendrimers, proteins, and nanoparticles. Permanent hydrophilicity was achieved without any additional treatment by tailored choice of the polymer components. Pores with several hundred nanometers to micrometers were obtained during the phase separation process. These pores can act as ink reservoirs. The porous stamps were thoroughly characterized by SEM, NMR, and contact angle measurement. The versatility of the porous stamps was shown in three printing schemes. First, positive microcontact printing was achieved by printing a polar thioether-modified dendrimer as the ink, followed by backfilling and wet etching. Second, the porous stamps were used for multiple printing of fluorescent proteins without reinking. Third, nanoparticles of about 60 nm in diameter, which cannot be directly transferred by oxidized PDMS stamps, were successfully printed onto substrates by using these porous stamps.