SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3728-5
Biological intelligence achieves exceptional energy efficiency and environmental adaptability, exemplified by the human brain's ~20 W resting power consumption. A key strategy is the use of multi-ions as signal carriers for transduction and processing. Iontronics, employing ions instead of electrons, offer a promising route to low-energy, heat-dissipation-free devices for memory, sensing, and neuromorphic computing. However, conventional iontronics require external voltage bias to drive ion motion, complicating miniaturization and integration. Here, we highlight a recent breakthrough by Guo et al. reporting a bias-free iontronic memory sensor ('memsensor') that operates by controlling surface ion migration. The device couples vanadium dioxide (VO2) with a low-work-function indium (In) patch. Upon immersion in NaCl solution, In3+ ions generated electrochemically within the Debye length are driven by the intrinsic surface electric field to diffuse into the VO2 surface, inducing an insulator-to-metal phase transition and a measurable, non-volatile change in surface conductance. This conductance state correlates with NaCl concentration and can be reversibly restored by H2O2 treatment. The memsensor emulates the gustatory plasticity of C. elegans, mimicking the response dynamics of ASEL and ASER neurons. In a proof-of-concept, a model boat equipped with the memsensor exhibits adaptive chemotaxis: after 'starvation' training in high NaCl concentration, it avoids high-concentration zones; conversely, after training in low concentration, it migrates toward high-concentration zones. This work demonstrates a bias-free strategy for programmable memory and sensing, potentially advancing autonomous microsystems and bioinspired electronics.
SCIENCE CHINA Materials•2026•DOI: 10.1007/s40843-025-3772-y
Conformal contact between functional electronic films and biological surfaces is critical for long-term device stability, high signal sensitivity, and favorable signal-to-noise ratio. Traditional transfer methods, such as soft stamps and pad printing, often involve mechanical pressing, leading to poor conformality, localized stress concentration, or structural failure. Alternative strategies, including geometric engineering of non-stretchable materials or using stretchable organic alternatives, mitigate these issues but increase design complexity and reduce fabrication efficiency. Here, we highlight a novel 'drop-printing' strategy introduced by Li et al. that leverages capillary force to manipulate a water droplet to pick up a thin film, transfer it to a target substrate, and print it onto the surface. As the droplet evaporates, the film conformally wraps the surface. The droplet acts as a lubricating layer, while interfacial liquid penetrating microstructures generates capillary pressure, facilitating shape-adaptive deformation and significantly reducing stress concentration. The final positioning and conformality are governed by droplet behavior on the target surface. This approach achieves positional deviation of less than 20 μm via regulation of three-phase contact lines. The strategy enables damage-free conformal wrapping of non-stretchable films onto three-dimensional biological surfaces, as demonstrated by drop-printed silicon microfilm conformally wrapping on a rat brain, with successful NIR laser stimulation triggering forelimb movement and synchronized brain electrophysiological signals. This gentle, high-precision method addresses the pressing need for low-stress conformal bioelectronics, offering a general solution for diverse biological interfaces.