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Artificial neurons that reproduce the rich dynamical behaviour of biological spiking are essential for neuromorphic hardware and biohybrid interfaces, yet scalable solution-processed devices with physiologically relevant spiking characteristics remain elusive. Here we demonstrate aerosol-jet-printed memristive networks of MoS2 nanosheets that exhibit thermally activated filamentary switching and snap-back negative differential resistance, enabling volatile threshold switching in fully printed graphene/MoS2/graphene devices on flexible substrates. In situ thermal imaging and circuit modelling reveal that current-constricted filaments formed through Joule heating govern the nonlinear switching dynamics. These printed memristors enable oscillatory and spiking neuron circuits with tunable frequencies up to 20 kHz and stable operation over more than 10^6 cycles. Simple neuristor circuits realize first-, second- and third-order spiking complexity, including integrate-and-fire behaviour, spike latency, tonic firing, class 1 excitability, tonic bursting and phasic dynamics. The generated spike waveforms match physiological timescales and stimulate Purkinje neurons in mouse cerebellar slices. Our results establish printed nanosheet memristive networks as a scalable platform for bio-realistic neuromorphic hardware and flexible brain–machine interfaces. 

Crystalline solids are governed by universal structure-property relationships derived from their crystal symmetry, leading to paradigmatic rules on what properties they can and cannot exhibit. A long-held structure-property relationship is that centrosymmetric crystals cannot differentially absorb circularly polarized light. In this study, we demonstrate the design, synthesis, and characterization of the centrosymmetric material Li2Co3(SeO3)4, which violates this relationship not by defying symmetry-imposed selection rules but by invoking a photophysical process not previously characterized for crystalline solids. This process originates from an interference between linear dichroism and linear birefringence, referred to as LD-LB, and involves strong chiroptical signals that invert upon sample flipping. In addition to enabling a chiroptical response under centrosymmetry, this process opens up photonic engineering opportunities based on crystalline solids.