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Understanding charge transfer processes between graphene and functional materials is crucial from the perspectives of fundamental sciences and potential applications, including electronic devices, photonic devices, and sensors. In this study, we present the charge transfer behavior of graphene and amine-rich polyethyleneimine (PEI) upon CO2 exposure, which was significantly improved after introduction of hygroscopic polyethylene glycol (PEG) in humid air. By blending PEI and PEG, the number of protonated amine groups in PEI was remarkably increased in the presence of water molecules, leading to a strong electron doping effect on graphene. The presence of CO2 gas resulted in a large change in the resistance of PEI/PEG-co-functionalized graphene because of the dramatic reduction of said doping effect, reaching a maximum sensitivity of 32% at 5,000 ppm CO2 and an applied bias of 0.1 V in air with 60% relative humidity at room temperature. This charge transfer correlation will facilitate the development of portable graphene-based sensors for real-time gas detection and the extension of the applications of graphene-based electronic and photonic devices.

The progress in developing the microelectromechanical system (MEMS) heater-based SnO 2 gas sensors was hindered by the subsequent heat treatment of the tin oxide (SnO 2 ), nevertheless it is required to obtain excellent sensor characteristics. During the sintering process, the MEMS heater and the contact electrodes can be degraded at such a high temperature, which could reduce the sensor response and reliability. In this research, we presented a process of preheating the printed SnO 2 sensing layer on top of a sacrificial bridge-type ZnO layer at such a high temperature, followed by transferring it onto the contact electrodes of sensor device by selective etching of the sacrificial ZnO layer. Therefore, the sensor device was not exposed to the high sintering temperature. The SnO 2 gas sensor fabricated by the transfer process exhibited a rectangular sensing curve behavior with a rapid response of 52 s at 20 ppm ethanol concentration. In addition, reliable and repeatable sensing characteristics were obtained even at an ethanol gas concentration of 5 ppm.

Sensors by MEMS technology in smart portable devices play an important role in corresponding to five human sensory systems, enhancing user convenience, and enriching user experience. The versatility of usage has led to a recent rapid development of sensor technology, resulting in commoditized sensors with low cost and high performance. Along with the smart deployment of those sensors, new types of MEMS sensors are always required for application in emerging areas such as autonomous vehicles, smart factories and so on. Recently, edge computing with a deep learning accelerator enables data filtering and classification. Although it shows a primitive level of context awareness for inferencing and decision-making, we believe that it will be one of the most important core technologies to accomplish smart loT, smart factory, and smart city technology. In our presentation, sensor technology and its evolution from devices to sensor-based services will be presented.

The order of the authors in the original version of this article was unfortunately incorrect on the first page and the first page of the ESM. Instead of Myungwoo Son1, Yusin Pak1, Sang-Soo Chee1, Francis Malar Auxilia1, Kihyeun Kim1, Byung-Kee Lee2, Sungeun Lee2, Sun Kil Kang2, Chaedeok Lee2, Jeong Soo Lee2, Ki Kang Kim3, Yun Hee Jang4, Byoung Hun Lee1, Gun-Young Jung1 (✉), and Moon-Ho Ham1 (✉) It should read Kihyeun Kim1,§, Myungwoo Son1,§, Yusin Pak1, Sang-Soo Chee1, Francis Malar Auxilia1, Byung-Kee Lee2, Sungeun Lee2, Sun Kil Kang2, Chaedeok Lee2, Jeong Soo Lee2, Ki Kang Kim3, Yun Hee Jang4, Byoung Hun Lee1, Gun-Young Jung1 (✉), and Moon-Ho Ham1 (✉)

We have described rapid, label free detection of Influenza A viruses with cantilever transducer modified with synthetic sialylglycopolymer as a receptor layer. Surface stress induced by binding of viruses to receptor layer was investigated as analytical signal. Synthetic sialylglycopolymer receptor layer can be implemented in nanoscale strain-gauge cantilever transducers for high sensitive viruse detection. Strain-gage transducers with such sensor layer demonstrate long lifetime, high sensitivity and regeneration possibility. Nanomechanical cantilever system with optical detector was used for surface stress measurements. We have shown that positive label free detection of Influenza A could be achieved at a concentration less than 106 viruses in ml, which is comparable to the detection sensitivity of polymerase chain reaction (PCR). However, in contrast to PCR, cantilever sensor detection was label free, in situ, and rapid (less than 30 min), potentially requiring minimal or no sample preparation.