Flexible Temperature Sensor Array Based on PEDOT:PSS Inkjet Printing

Inkjet-printed micro-electro-mechanical systems are a set of fabrication techniques that use inexpensive printed circuit processes to construct microsensors. Compared with traditional sensors, flexible micro-sensors present excellent application prospects in the fields of medical electronics, environmental monitoring wearable devices, etc. This article developed a simple flexible temperature sensor array based on inkjet-printed micro-electro-mechanical systems by using poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS) as the sensing material. This sensor array employed polyethylene terephthalate (PET), nine silver contact electrodes, and 12 PEDOT:PSS sensing blocks as the bottom substrate, middle layer, and top layer, respectively. There are 12 temperature sensors arrayed on an area of $4\times 4$ cm2, which can realize a thermal resolution of $5\times 5$ temperature pixels using the modeling simulation method. The sensor array showed a sensitivity of -0.50%/°C with a small hysteresis from 25 up to $75~^{\circ }$ C (or in a chosen temperature range), which is higher compared to that of other similar sensors reported in the literature. To improve the accuracy, an array correction algorithm was investigated as a data processing method and succeeded in reducing the temperature error from 0.80% to less than 0.50%. The combination of the array and flexible structures makes our temperature-sensing arrays easy to affix and particularly advantageous for displaying interface heat diffusion behavior, such as the water body’s epidermis.

I. Introduction

With the application of flexible electronic printing technology to sensors, flexible sensors possess higher adaptability and flexibility compared to traditional sensors. Traditional electronic products equipped with this new generation of sensors can also have better performance in the fields of healthcare [1], [2], [3], robotics [4], [5], environmental monitoring [6], [7], food quality testing [8], [9], and microelectronic systems [10], [11]. Photolithography [12], [13] and printing [14], [15] are common fabrication techniques for flexible sensor construction. Photolithography allows for repetitive fabrication of high-performance devices but incurs high manufacturing costs due to the need for clean rooms and large consumable expenditures [16], [17]. Screen printingis a common manufacturing technique used in laboratories as it allows for the manufacturing of sensors to be efficient, reproducible, and cost-effective. However, depending on the size, layout, and appearance of the sensors, different mask plates need to be designed and manufactured, making the pre-design of the sensors relatively cumbersome [18]. Therefore, there is a need for an inexpensive printing technology with significantly lower manufacturing costs and higher productivity. Inkjet printing technology [19], [20], [21] has gradually attracted more and more attention from researchers in recent years as it avoids the use of stencil masks or clean room lithography. It can accurately and continuously deposit micro/nanomaterials onto a wide range of substrates under standard environmental conditions and can rapidly and cost-effectively print different graphics with high resolution, without the assistance of a mask.