Fabrication And Properties Of Dextran-based Ultraflexible Degradable Organic Synaptic Transistors

Flexible synaptic transistors can not only realize the basic functions of neural networks such as information storage,neuromorphic computing and image recognition,but also have the advantages of portability,wearability and implantability,exhibiting the broad prospects in next-generation brain-machine interfaces,soft robots and wearable computing.The inherent rigid nature of inorganic materials inevitably limits the mechanical flexibility and bending stiff ness of the conventional synaptic transistors,which impedes the further development of synaptic devices in flexible electronics.Benefiting from the advantages of organic materials such as mechanical flexibility,light weight and low cost,organic synaptic transistors can integrate seamlessly with the 3D-object surfaces.It provides an opportunity for flexible devices to develop towards ultra-flexibility,and it will attract more and more attention in the future of electronic skin and implantable artificial neural networks.However,most of the current organic synaptic transistors are usually made of non-degradable materials.When the device is discarded,it will produce electronic wastes(e-waste),and results in environmental pollution and waste of resources,which is contrary to the development concept of “green”electronics.Aiming at these challenges,this work screened a biodegradable neutral polysaccharide—dextran as the dielectric layer of organic synaptic transistors,fabricating the ultraflexible self-supporting synaptic transistors via a peeling-off method,and explored its simulation of synaptic functions.The main contents are listed as follow:1.Based on the degradable dextran dielectric layer,organic synaptic transistors were fabricated,and their basic synaptic functions were systematically explored.Through the characterization of the mechanical properties,electrical properties and degradation characteristics of the dextran membranes,the feasibility of applying dextran membranes to ultraflexible degradable synaptic transistors is investigated.The synaptic devices can successfully simulate the basic synaptic functions such as EPSC,STP,LTP and potentiation/depression curve of synaptic weight.2.The working mechanism of our synaptic transistors is explored in terms of the water content and hydroxyl content of dextran dielectric for the first time.Proton conduction behavior has been discovered in the neutral polysaccharide by adjusting the environmental humidity and the cross-linking degree of dextran membranes.The results confirm that the self-dissociation of water and the existence of hydrogen bond network are the root causes of proton conduction in neutral polysaccharides.3.309 nm ultraflexible self-supporting organic synaptic transistors were fabricated through a simple peeling-off method,and they can be rapidly degraded after completing their specified functions.The synaptic devices can remain stable electrical characteristics under the different bending radii.Even under a bend radius as low as 150 ?m,the ultraflexible devices still can maintain the transfer characteristics and potentiation/depression curve of synaptic weight.Finally,when the device needs to be degraded quickly,it can completely disappear in the water within 15 seconds without any toxic and harmful byproducts.