Biomaterial-based inks have been developed that respond to chemicals released from the body (e.g. in sweat) by changing color. The inks can be screenprinted onto textiles such as clothes, shoes, or even face masks in complex patterns and at high resolution, providing a detailed map of human response or exposure. The technology could simultaneously detect and quantify a wide range of biological conditions, molecules, and possibly pathogens over the surface of the body using conventional garments and uniforms.
Wearable sensing devices have attracted considerable interest in monitoring human performance and health. Many such devices have been invented incorporating electronics in wearable patches, wristbands, and other configurations that monitor either localized or overall physiological information such as heart rate or blood glucose. The new bio-inks provide non-electronic, colorimetric detection of a theoretically very large number of analytes using sensing garments that can be distributed to cover very large areas: anything from a patch to the entire body and beyond.
The components of the sensing garments possible are biologically activated silk-based inks. The soluble silk substrate in these ink formulations can be modified by embedding various “reporter” molecules such as pH-sensitive indicators or enzymes like lactate oxidase to indicate levels of lactate in sweat. The former could be an indicator of skin health or dehydration, while the latter could indicate levels of fatigue of the wearer.
Many other derivatives of the inks can be created due to the versatility of the silk fibroin protein by modifying it with active molecules such as chemically sensitive dyes, enzymes, antibodies, and more. While the reporter molecules could be unstable on their own, they can become shelf-stable when embedded within the silk fibroin in the ink formulation.
The inks are formulated for screenprinting by combining with a thickener (sodium alginate) and a plasticizer (glycerol). The screen-printable bio-inks can be used like any ink developed for screen-printing and applied not just to clothing but also to various surfaces such as wood, plastics, and paper to generate patterns ranging from hundreds of microns to tens of meters.
While the changes in color presented by the inks can provide a visual cue to the presence or absence of an analyte, use of camera imaging analysis scanning the garments or other material can gather more precise information on both quantity and high-resolution, submilli-meter mapping.