Stretchability and self-healing ability are essential attributes of modern electronic sensors for wearable applications. Herein, intrinsically ultrastretchable, self-healing and transparent humidity sensors composed of ionic κ-carrageenan/polyacrylamide (PAM) double network (DN) organohydrogels are fabricated via a facile solvent-exchange strategy. Hygroscopic ethylene glycol (EG) and glycerol (Gly) are introduced in the organohydrogels to promote both anti-drying and humidity sensing capabilities. The organohydrogel sensors display unprecedented stretchability (1225% strain) and excellent sensing performance, including fast response (0.27 s) and recovery time (0.3 s), wide relative humidity (RH) detection range (4–90%), stability and linearity. The conductance of Gly-DN sensors increases more than 543 times with increasing RH from 4% to 90%. With sufficient sensitivity, the humidity sensors can monitor human respiration with stable and repeatable output. The enhanced sensitivity and moisture-holding ability are attributed to the ready formation of hydrogen bonds between water molecules and enormous hydrophilic groups, including –OH, SO₃ ⁻ and –NH₂, in the elaborate polymer networks and binary solvent. The hindering effect of polymer chains on the transport of conductive ions plays a key role in producing a transducing signal, which is proposed as the mechanism of the novel sensors.

Cancer is one of the leading causes of human death, despite enormous efforts to explore cancer biology and develop anticancer therapies. The main challenges in cancer research are establishing an efficient tumor microenvironment in vitro and exploring efficient means for screening anticancer drugs to reveal the nature of cancer and develop treatments. The tumor microenvironment possesses human-specific biophysical and biochemical factors that are difficult to recapitulate in conventional in vitro planar cell models and in vivo animal models. Therefore, model limitations have hindered the translation of basic research findings to clinical applications. In this review, we introduce the recent progress in tumor-on-a-chip devices for cancer biology research, medicine assessment, and biomedical applications in detail. The emerging tumor-on-a-chip platforms integrating 3D cell culture, microfluidic technology, and tissue engineering have successfully mimicked the pivotal structural and functional characteristics of the in vivo tumor microenvironment. The recent advances in tumor-on-a-chip platforms for cancer biology studies and biomedical applications are detailed and analyzed in this review. This review should be valuable for further understanding the mechanisms of the tumor evolution process, screening anticancer drugs, and developing cancer therapies, and it addresses the challenges and potential opportunities in predicting drug screening and cancer treatment.