Here, ratiometric sensing approaches can improve the accuracy of a sensor by compensating for variations in mechanical movements and variations of excitation intensities. Further, multiplexing of sensors presents interesting opportunities for sensing different analytes in complex environments. As a lightweight and inexpensive substrate, paper has been widely used for sensing approaches. By using a wax printing method, it was possible to design custom SWCNT-based barcodes on paper substrates, that can be fixed on other substrates (Figure ). Additionally, microarrays can be printed on substrates such as glass. For example, the deposition of nanoliter volumes leads to spot sizes in the order of approx. 210 µm with spot heights of approx. 50 nm (Figure ). Interestingly, the sensitivity of the nanotubes is often not limited by the SWCNT chemistry but by the detector size needed to accommodate the image. Therefore, using a higher imaging magnification can sometimes increase the detection limit by one order of magnitude at the expense of a smaller field of view. A third option is the incorporation of multiple different sensors into a hydrogel or another type of polymer (Figure ). This approach is very useful in complex mixtures to identify bacteria based on their chemical fingerprint, which is crucial for biomedical diagnostics. Here, the hydrogel can also serve as another design parameter for example by affecting the diffusion of the analytes to the sensors.