Flexible Alternating-Current Electroluminescent Devices for Reliable Identification of Fingerprints

Flexible bioelectronic devices, which can directly detect various external stimuli or biosignals and communicate the information to the users, have been broadly investigated due to the increasing demand for wearable devices. Among them, alternating-current electroluminescence (ACEL) devices are proposed as sensitive sensing systems for various targets, such as fingerprints. Herein, we propose a method for preparing high-performance ACEL devices by using an Ag electrode, polyethylene terephthalate (PET) substrate, FKM/EMI ionogel, and ZnS:Cu/BaTiO₃/Ecoflex emissive layer. Their influence has also been studied for achieving high performances. The results demonstrate that the prepared ACEL devices can achieve high performances of emitting bright green and blue light when contacted with various ionic liquids. Significantly, they achieved good sensing performance for detecting Na⁺ with a limit of detection at 17.1 μM in the linear range of 100-800 mM. Moreover, the ACEL devices can be used for identity recognition, as they are capable of efficient collection and distinguishing of fingerprints. Even the characteristics of fingerprints collected from bending surfaces or contaminated fingers could be distinguished by the naked eyes. Compared with commercial fingerprint devices, our ACEL devices exhibit superior performance in fingerprint identification. High-resolution and three-dimensional image analysis further validates the reliability of our ACEL devices in fingerprint collection and identification. As such, we believe that the designed ACEL devices have very promising application prospects in many fields.