Prior to digitalization, stamping was ubiquitous in everyday life – examples include the application of postmarks and seals or the validation of tickets for public transport. Stamping has also emerged as a versatile technique to micropattern substrates in materials science, in nanotechnology and microtechnology as well as in industrial production processes because stamping enables simultaneous patterning of large substrate areas. Therefore, stamping is a “parallel” micropatterning method – in contrast to serial patterning approaches like inkjet printing, which involve pixel-by-pixel writing. Stamping may involve embossing or lithographic deposition of ink. In the latter case, stamping is referred to additive. Up to now, parallel additive substrate patterning by ink deposition has typically been carried out using solid elastomeric stamps with topographically micropatterned contact surfaces. Ink is adsorbed onto the outer stamp surfaces. The quality of the deposited patterns deteriorates already after a few successive stamp-substrate contacts because of ink depletion. The unsolved problem of ink replenishment impedes the upscaling of stamping-based parallel additive substrate patterning. Moreover, only limited amounts of ink can be deposited onto counterpart substrates by classical stamping methods, and the possibilities to stamp environmentally friendly aqueous inks are limited also.
Project “Insect-inspired capillary nanostamping” (INCANA) exploits a bioinspired approach to overcome the drawbacks of state-of-the-art parallel additive stamping. Insect feet adhere to vertical walls and ceilings by contact formation via a large number of hairy contact elements. The insects deploy secretions for adhesion management through channels in their hairy contact elements to the contact interfaces. After detachment of the insect feet, arrays of secretion droplets remain on the counterpart surface. Artificial stamps mimicking insect feet, which are penetrated by spongy-porous pore systems enabling ink supply to the contact surfaces anytime during stamping, may overcome the drawbacks of state-of-the-art microcontact printing. However, only limited efforts to prepare such porous stamps had been reported prior to the start of project INCANA. In the course of project INCANA, porous capillary stamps with topographically micropatterned contact surfaces consisting, for example, of polymers, resins, silica glass and metals were designed. Using these porous stamps, insect-inspired capillary nanostamping was developed for the parallel and additive high-throughput deposition of a broad range of aqueous and nonaqueous inks. Capillary nanostamping can be carried out manually under ambient conditions or continuously in automated devices. Since ink can be supplied anytime during stamping, no interruptions for ink replenishment are required, and real additive patterning of counterpart substrates by deposition of three-dimensional ink structures is possible. Capillary nanostamping may yield functionalized substrates for optics, electronics, sensing, bioanalytics, clinical diagnostics, lab-on-chip configurations or tissue engineering. Wettability, self-cleaning properties and adhesive properties may be tailored in this way.
