## Conclusions  
Imprinting strategies lead to highly selective polymers that have excellent properties for chemical sensor applications for analytes ranging from below 1 nm up to some \(\upmu\)m. The ability to distinguish closely related species from each other is demonstrated with the selectivity between different xylene isomers on the molecular level. Larger analytes include different human rhinovirus (HRV) serotypes or erythrocytes of different blood groups. In both cases the analyte species share their geometrical features and differ exclusively by their respective surface chemistry. Nonetheless the surface imprints clearly distinguish both between different HRV serotypes and different blood groups. Imprints towards erythrocytes were realized by using cell ghosts as templates, because they are mechanically more rigid and stable and thus give more accurate images of the cell surface on the imprint. Finally, imprinting is also suitable for chemical sensing in highly complex mixtures, where very appreciable selectivity and sensitivity can be achieved by combining imprinted titanates with 100-MHz surface transverse wave resonators. Experimental section  
_Xylene sensors:_ For the xylene imprints we mixed 210 ul of divinylbenzene (DVB), 90 ul of styrene, 3 mg of azo-isobutyronitrile (AIBN) and 4.4 mg biphenyl - a porogen - with 100 ul template xylene and spin-coated the device of interest with it. Polymerization took place over night at 40 degC in saturated solvent atmosphere. Finally, the biphenyl was removed by washing with o-xylene and drying at 150 degC  
_Engine Oil Degradation:_ We synthesized degradation-sensitive titanate sol-gel layers by dissolving 50 ul tetrabutoxytitanate with 1 ml butanol and adding 10 mg of the template capric acid and 10 ul of water. After one hour pre-hydrolysis at 70 degC and three days at room temperature we added 6 ul of 0.1M HCl and 20 ul of water and heated at 70 degC for one hour followed by two days polymerization at room temperature. The resulting solution was drop-coated directly onto the sensitive area of the SAW. _HRV imprints:_ A diluted virus suspension in 10 mM Tris*HCl pH= 7.2 is used for stamp preparation. For this purpose 3 ul of this suspension are placed on a glass disc and incubated at 4 degC for 30 min. Afterwards the stamp is spun off at 2000 rpm and covered with the modifier consisting of a 10 mM solution of phloroglucinol and phenylenediamine in THF. In parallel, a QCM is spin-coated with 15 ul of a 1:10 dilution of the polyurethane (50.4 mg bisphenol A, 11.1 mg phloroglucinol and 38.4 mg hexamethylene-diisocyanate) in THF at 3000 rpm to yield layer heights around 250 to 350 nm (10-14 kHz). The stamp is then immediately pressed into the material. After 48 hours of hardening, the QCM is put into water at 50 degC for approx. 1h to lift off the stamp followed by stirring in 0.5 M HCl to unhinge the viruses from the polymer. _Erythrocyte imprints:_ Erythrocyte ghosts were produced by using the osmotic effect (lysis) by treating the RBC in a hypertonic NaCl solution for some minutes, which makes cells bursting. The cell contents were washed out by centrifugation in distilled water until the supernatant solution remained clear. After self-assembling on a stamp, the ghosts were pressed into a spin-coated polyurethane film consisting of 50.4 mg bisphenol A, 11.1 mg phloroglucinol and 38.4 mg hexamethylene-diisocyanate that have been mixed at room temperature and directly used for spin-coating. After polymerization over night, the stamp material can be removed by washing with hot water and the template with a 0.5% solution of sodium dodecyl sulfate in water. _Measurements:_ We prepared the QCM devices by screen printing the desired electrode pattern onto an AT-cut quartz blank and burning it at 400 degC. For the final sensor setup, the quartz is introduced into a custom-made oscillator circuit as frequency-determining element.