Fig. 2: Switchable stiffness iontronic mechanogate.
From: Mechano-gated iontronic piezomemristor for temporal-tactile neuromorphic plasticity
a Chemical structures of reacted precursor components within the bicontinuous heterogel. b Structural features of the stiffness iontronic mechanogate based on a bicontinuous heterogel. The vitrimer (orange) and ILgel (blue) domains formed bicontinuous structure through mutual interpenetration. c Three-dimensional finite element analysis of the bicontinuous heterogels with distinct stiffness states. The bicontinuous heterogel exhibits distinct strain-induced structural variations in stiff and soft states under compression (ε = 50%), where the effective cross-sectional area of the ILgel phase (SILgel) and Vitrimer phase (SVitrimer) undergo opposite changes, leading to bidirectional piezoresistive behaviors. d The current signal (I) of the heterogel mechanogate. The negative and positive piezoresistivity characteristics correspond to the stiff and soft states, respectively. e The stiffness-induced piezoresistivity (ΔIp/ΔIo, where ΔIp and ΔIo corresponding to the current of mechanogate under loading and unloading pressure, respectively) features of the iontronic mechanogate, demonstrating the negative and positive sensitivity (S). f The segment stability test of bidirectional piezoresistivity under the step-up pressure from 0 kPa to 50 kPa. g Negative and positive piezoresistive signal responses of the bicontinuous heterogels under cycle loading (loading pressure: 10 kPa, 20 kPa, 50 kPa). The inset shows the statistics of piezoresistivity features in existing typical pressure sensors (including ion hydrogel, ILgel, nanocomposite, conductive polymer, aerogel and liquid metal) and the heterogel. Distinguished from their unidirectional piezoresistive features, our mechanogate demonstrates a bidirectional stiffness-gated piezoresistivity.
