In various optical sensor applications, programmable analog filters are desirable to reduce the hardware requirement. Memristor is two state programmable nonvolatile resistor, which has a small size and low power consumption. Using these resistance switching characteristics of a memristor, we propose a novel memristor-capacitor (MC) based printed low pass and high pass filters for analog circuits to achieve tunable cut-off frequencies and bandwidth. The cut-off frequencies of filters are controlled through a memristor state switching (HRS/LRS), whereas the capacitor has a fixed value. The proposed MC filters utilize graphene/poly 4-vinlyphenol (G/PVP) for dielectric layer of capacitors and Graphene Quatum Dots (GQDs)/PVP for an active layer of memristor, and these layers are fabricated on ITO coated flexible PET substrate through electrohydrodynamic (EHD) technique. Both MC filters are designed as parameters of two state memristance and a capacitance. From comparison between designed and fabricated filters, we show that they are matched quite well.
We propose a novel flexible and stackable resistive random access memory (ReRAM) array with multi-layered crossbar structures fabricated on a PET flexible substrate through EHD system. The basic memory block of the proposed device is based on one resistor and multi-layered column memristors (1R-MCM) structure, which can be easily extended to 3 dimensional columns for a high integration. To fabricate the device, the materials Ag for top and bottom electrodes, PVP for memristor, and (MEH:PPV and PMMA in acetonitrile) for pull-up resistors are used. Memory single cell is consisted of a high OFF/ON ratio (~4663) memristor and a pull-up resistor (20 MΩ) that operate on the principles of voltage divider circuit. Memory logic data is retrieve in the form of voltage levels instead of sensing current the of crossbar array. Two memory crossbar arrays are stacked vertically and they are sharing column bars, each column’s memristors are with a single pull-up resistor. A 3x3 stacked memory with two layers that can store 18 bits of data is demonstrated to realize on a small area for a high integration.
In this paper, a single layered passive photo sensor based on perylene/graphene composite is proposed, which is deposited in comb type silver electrodes separated as 50 μm spacing. To increase an electrical conductivity of the proposed sensor, perylene and graphene are blended. Photo sensing layer (120nm thick) and Silver electrodes (50 μm width, 350 nm thick) are deposited on poly(ethylene terephthalate) (PET) substrate through electro-hydrodynamic (EHD) system. The proposed photo sensor detects a terminal resistance inversely varied by an incident light in the range between 78 GΩ in dark and 25 GΩ at light intensity of 400lux. The device response is maximum at 465 nm ~ 535 nm wavelength range at blue light. The device exhibited bendability up to 4mm diameter for 1000 endurance cycles. The surface morphology analysis is carried out with FE-SEM and microscope.
We propose a stretchable photo sensor fabricated on uniform ridged polydimethylsiloxane PDMS substrate through electro-hydrodynamic (EHD) technique. An active layer, perylene/graphene composite thin film (67nm) is sandwiched between top and bottom ITO electrodes. The electrical conductivity of the perylene is enhanced by blending with graphene. The photo sensor changes the terminal resistance from 108MΩ to 87MΩ against light intensity of 0~400lux, respectively. To verify a stretchability, the proposed photo sensor under mechanical strain of 25% is normally worked, and it is stretchable up to 50% strain, maximally. A mechanical bendability test is carried out by folding the device for 1000 endurance cycles, while there is no change in the electrical behavior.