A Self-Sustained Wireless Multi-Sensor Platform Integrated with Printable Organic Sensors for Indoor Environmental Monitoring

Abstract

A self-sustained multi-sensor platform for indoor environmental monitoring is proposed in this paper. To reduce the cost and power consumption of the sensing platform, in the developed platform, organic materials of PEDOT:PSS and PEDOT:PSS/EB-PANI are used as the sensing films for humidity and CO₂ detection, respectively. Different from traditional gas sensors, these organic sensing films can operate at room temperature without heating processes or infrared transceivers so that the power consumption of the developed humidity and the CO₂ sensors can be as low as 10 μW and 5 μW, respectively. To cooperate with these low-power sensors, a Complementary Metal-Oxide-Semiconductor (CMOS) system-on-chip (SoC) is designed to amplify and to read out multiple sensor signals with low power consumption. The developed SoC includes an analog-front-end interface circuit (AFE), an analog-to-digital convertor (ADC), a digital controller and a power management unit (PMU). Scheduled by the digital controller, the sensing circuits are power gated with a small duty-cycle to reduce the average power consumption to 3.2 μW. The designed PMU converts the power scavenged from a dye sensitized solar cell (DSSC) module into required supply voltages for SoC circuits operation under typical indoor illuminance conditions. To our knowledge, this is the first multiple environmental parameters (Temperature/CO₂/Humidity) sensing platform that demonstrates a true self-powering functionality for long-term operations.

Keywords: SoC; power-gating; printable organic sensors; self-sustained; sensing platform.

Figure 1

The application scenario of the developed sensing platform with a sensor card that includes sensors for temperature, CO₂, and humidity detection.

Figure 2

The block diagram of the designed system-on-chip (SoC) sensing platform with a replaceable sensor card.

Figure 3

The control flow chart and the timing diagram.

Figure 4

(A) The measured characteristics of the designed humidity sensor; (B) The measured characteristics of the designed CO₂ sensor.

Figure 5

The die photo of the designed SoC and its measured performance.

Figure 6

(A) Humidity and (B) CO₂ concentration measurement results from the developed sensing platform.

Figure 7

The measured data, including temperature, CO₂ and humidity concentration, received from the developed indoor environmental sensing platform can be transferred to a cloud server and browsed from a website.