Wearable flexible electronic devices rely on flexible, stretchable materials. In recent years, due to its application prospects, a lot of attention has been gained. However, there are many drawbacks to using traditional processing techniques. Recently, Professor Bao Zhenan's team at Stanford University prepared a flexible field-effect transistor with high field-effect mobility and low threshold voltage through inkjet printing technology, and used its ion type switching period to simulate the transmission of information between synapses. A related paper entitled "Inkjet-printed stretchable and low voltage synaptictransistor array" was published in "Nature Communication".
The layer-by-layer inkjet printing technology was used to prepare the stretchable conductive material into a triode structure. PVDF-HFP was used as the gate electrolyte, and PEDOT: PSS was used as the source electrode after Plasma activation. SC-SWCNTs and conjugated polymers were then used as semiconductor channels, and then PEDOT: PSS and PVDF-HF were printed on them to form sandwich structures.
For field-effect transistor materials, the lower the threshold voltage, the lower the operating voltage; and the higher the field-effect mobility, the faster the switching rate. According to the Ids-Vds transfer characteristic curve, the device has a very high field effect mobility, with an average of 27 ± 5 cm2 V-1 s-1, and its switching current ratio can be 104. Its high field-effect mobility provides a very low threshold voltage. At the same time, its high transconductance characteristic gm, which averages 47 ± 9 μS (Vds = 1.1V), also supports lower operating voltages. Its high field-effect mobility results from its double-layer structure as a gate electrolyte PVDF-HFP ionic polymer. As a flexible electrode, because the structure of the connecting part between the gate electrodes is easily broken, its performance cannot maintain its properties within the range in which it should be stretched, because its stretching direction is perpendicular to the carbon nanotubes. At the same time, the response characteristics and response period of Ids to Vgs can be matched with the information transmission between synapses, which can be used to simulate the information transmission between synapses.
Electronic materials that are additively manufactured in transistors using the same inkjet printing technology all have inherent tensile properties.
Inkjet printing was used to prepare stretchable single-walled carbon nanotube field effect transistor (SWCNT-FET) arrays. 1. Apply a layer of poly (4-styrene sodium sulfonate) (PSS) as a sacrificial layer on a silicon wafer substrate, and then inkjet print PVDF-HFP as the gate electrolyte. 2. The surface is treated with plasma. 3. Print PEDOT: PSS on PVDF-HFP as the underlying source-drain electrode. 4. Print polymer-encapsulated SC-SWCNTs. 5. Wash away the sorting polymer. 6. Print PEDOT: PSS as the top source-drain electrode. 7. Print PVDF-HFP for packaging. 8. Spin-coated a layer of thermoplastic styrene-ethylene-butene-styrene (SEBS) elastomer to make a system-level package. 9. Spot-print pure toluene to make holes in the SEBS packaging layer above the source. 10. Multi-wall carbon nanotube conductive ink filled with DMF as a solvent. 11. Surface plasma treatment. 12. Print PEDOT: PSS. 13. Construct a SEBS flexible substrate. 14. Dissolve PSS. 15. Take it off. 16.plasma processing. 17. Print grid electrode: PEDOT: PSS.
Characterization of the electrical properties of inkjet printed field-effect transistor a. Transfer characteristic curve and change curve with gate voltage of stretchable single-wall carbon nanotransistor FET (SWCNT-FET); b. Maximum source-drain current in saturation region of 35 array FET Histograms; c. Output characteristic curves of FETs with an aspect ratio of 1000m / 50m at different gate voltages; d. Transfer characteristic curves of FETs vertically (left) and parallel (right) under carbon nanotube stretching. E. Histogram of Maximum Source-Drain Current at 32% Array Saturation Region under Unstretched and Different Direction Strains to 10%
IJ-FET simulates the transmission of information between synapses a. The change in source-drain current corresponding to a small gate voltage pulse within a certain period of time; b. The post-synaptic current change under 32 gate voltage pulses, the pulse increases, and the current changes Increasing, the pulse disappears, and the current recovers; c. Within a certain time, the pulse voltage is applied to the current change under the gate electrode.