Colloidal single-walled carbon nanotube (SWCNT) optical sensors are capable of highly sensitive and selective molecular recognition for varying classes of analytes. However, their incorporation into commercial uses requires the study of their packaging or form factors necessary for specific applications. Here, we have showcase two techniques that are steps toward incorporating these materials for both industrial and field applications. First, we study the immobilization of SWCNT sensors on seven different types of paper substrates. Sensors remain functional upon immobilization for up to 60 days with storage technique dictating sensor longevity. With a wax printing method, we are able to form one-dimensional barcodes that allow for rapid reading of sensor elements. Using a sensor array of ssDNA wrappings, we are able to differentiate in test solutions between Cu(II), Cd(II), Hg(II), Pb(II) at a concentration of 100 µM.
Next, we design and characterize a compact, integrated fiber optic nanosensor probe element (optode) for pharmaceutical applications. The smaller form factor of the optode system is designed to facilitate incorporation into on-line or at-line biopharmaceutical processes. The sensor tip itself consist of fibers that provide both excitation and emission. Together with a 3D printed capsule, we embed SWCNT sensors in a protective and porous hydrogel for the sampling of a production stream. By adjusting the crosslinking density of the hydrogel, we are able to extract time dependent sensor responses as a function of analyte size. Using this platform with a SWCNT sensor sensitive to IgG, we are able to resolve the relative fraction of monomers versus dimer aggregates in under 5 minutes of analysis.
