Fig. 4

Non-volatile liquid-interactive sensing memory. a Schematics of the device structure for liquid sensing memory. An liquid-interactive ferroelectric sound (LIFS) arising from remnant polarisation of a liquid (P_r-L) developed in the write step is read in terms of SPL with a reference PEDOT:PSS solution in water. b Sound pressure level (SPL) values of LIFSs written with five liquids with different polarities and subsequently read with the reference PEDOT:PSS solutions after removal of the liquids. c Write-erase cycle endurance of an LIFS alternating current (AC) device with deionised water. SPL value arising from the LIFS of deionised water was substantially reduced after erasing the written remnant polarisation. Re-writing of the device with deionised water resulted in an SPL value almost identical to that in the first writing step. Ten write-erase cycles were reliably achieved with significant variation of SPL. d Variation of SPL values of an LIFS AC device upon multiple cycles of consecutive write with deionised water, erase, re-write with ethanol, and erase. Two characteristic SPL values of 65 and 55 dB written with deionised water and ethanol, respectively, are apparent after the multiple cycles. e Time-dependent retention of SPL value arising from an LIFS of deionised water. Direct current (DC) voltages of 2 and −1 kV were used for writing and erasing for all the liquids, respectively. The reading was obtained for all the liquids at an AC frequency and voltage of 20 kHz and 100 V, respectively. The electrode spacing of all samples is 12 mm