A fully roll-to-roll gravure-printed carbon nanotube-based active matrix for multi-touch sensors

Abstract

Roll-to-roll (R2R) printing has been pursued as a commercially viable high-throughput technology to manufacture flexible, disposable, and inexpensive printed electronic devices. However, in recent years, pessimism has prevailed because of the barriers faced when attempting to fabricate and integrate thin film transistors (TFTs) using an R2R printing method. In this paper, we report 20 × 20 active matrices (AMs) based on single-walled carbon nanotubes (SWCNTs) with a resolution of 9.3 points per inch (ppi) resolution, obtained using a fully R2R gravure printing process. By using SWCNTs as the semiconducting layer and poly(ethylene terephthalate) (PET) as the substrate, we have obtained a device yield above 98%, and extracted the key scalability factors required for a feasible R2R gravure manufacturing process. Multi-touch sensor arrays were achieved by laminating a pressure sensitive rubber onto the SWCNT-TFT AM. This R2R gravure printing system overcomes the barriers associated with the registration accuracy of printing each layer and the variation of the threshold voltage (Vth). By overcoming these barriers, the R2R gravure printing method can be viable as an advanced manufacturing technology, thus enabling the high-throughput production of flexible, disposable, and human-interactive cutting-edge electronic devices based on SWCNT-TFT AMs.

Fully Printed and Encapsulated SWCNT-Based Thin Film Transistors via a Combination of R2R Gravure and Inkjet Printing

“…One method of assessing stability is by monitoring the output of a printed inverter circuit in response to digital ("0" and "1") input signals. 4,42,50 Variation will dictate the complexity of a circuit that can be realized with the present process technology and determine the suitability of printed TFTs in the target application. 4,42,50 Transfer curves from 20 encapsulated fully printed devices along a row show minimal variation ( Figure 9a).…”

“…4,42,50 Variation will dictate the complexity of a circuit that can be realized with the present process technology and determine the suitability of printed TFTs in the target application. 4,42,50 Transfer curves from 20 encapsulated fully printed devices along a row show minimal variation ( Figure 9a). The fully printed encapsulated device was used to construct an inverter (Figure 9b −1 s −1 using the estimated capacitance of 6.5 nF cm −2 .…”

“…42 These results strongly indicate that the process reported here can be used to construct practical devices including logic circuits with improved mobility and oncurrents and can further expand the application space in printed electronics. 4,50 …”

Nanomaterial‐Enabled Wearable Sensors for Healthcare

“…An array of resistive pressure sensors can be integrated with an active matrix backplane to enable low-signal-crosstalk spatial pressure mapping. In nanomaterial-enabled active matrix pressure sensing, nanomaterials such as Ge/Si NWs [85] or semiconducting CNTs, [63,64,84] can be employed as the channel material for the transistor. Figure 5c shows a representative work using CNT based TFTs and pressure-sensitive rubber (PSR) for active matrix pressure sensing.…”

“…Direct spinning of CNTs onto a substrate or into yarns [53][54][55] and electrospinning of nanofibers or NWs were reported to produce fiber-like nanomaterials. [56][57][58][59] In addition, novel direct printing or writing techniques [60,61] such as inkjet printing, [62] gravure printing, [63,64] screen printing, [65][66][67] nozzle jet printing, [26] and direct writing [68,69] enabled the fabrication of wearable sensors that possess complex patterns with high resolution.…”