4:00pm - 4:30pmInvited
Printed Graphene Sensors
National Electronics and Computer Technology Center, Thailand
Graphene, emerging as a true 2-dimensional material, has received increasing attention due to its unique physicochemical properties (high surface area, excellent conductivity, high mechanical strength, and ease of functionalization and synthesis). Printed Electronic also is a new wave of large-area electronics and flexible electronics manufactured by printing technology. Regarding printing method, organo-functionalized graphene inks may be deposited by screen printing, inkjet printing, aerosol jet printing, nano-imprinting, gravure printing, flexography and offset printing. The fusion of these two emerging technologies created the new opportunity to invent variety of novel electronic devices with low cost including nanosensors. Recent development on printed graphene sensors are comprehensively presented. Printed graphene based biosensors exhibited promising properties with good reliability suitable for commercial applications such as food pathogen sensors, biomedical sensors etc.
4:30pm - 4:45pmOral
Transparent, Surface Texture Change Device for Tactile Feedback
1School of Materials Science and Engineering, Nanyang Technological University, Singapore; 2School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore; 3Energy Research Institute @ NTU (ERI@N), Nanyang Technological University, Singapore
Human hand can feel variations in friction, hardness, temperature and fine and macro roughness to perceive as the texture change. Various developments in the field of tactile perception has happened and technologies like Electrostatic, Piezoelectric, Vibration motors, Air jets, Surface acoustic waves, Electroactive polymers, Peltier elements and Pressure valves have been researched. Most of these technologies work to simulate the tactile feeling rather than creating the physical changes.
Electroactive polymers (EAPs) are polymers that respond to electrical stimuli by changing shape or size. Under the family of EAPs, Dielectric elastomer actuators (DEAs), thin elastomeric layer sandwiched between compliant electrodes, have been known to produce large deformations. Compliant electrodes are critical to DEAs. These systems are capable of making the physical changes rather than simulating the effect or feel of touch. Tactile feedback is not because of the manoeuvre, rather the physical changes happen because of the working principle of DEAs. Carbon electrodes based DEAs have been demonstrated for tactile applications, based on actuation in vibration mode. Transparent electrodes like AgNW, CNTs and Graphene have been used recently as well for DEA systems.
We demonstrate a hybrid, compliant electrode system for “Transparent, Surface Texture change device” based on hydrogels and AgNW-Pedot: PSS. DEAs operate in thickness mode actuation; the in-plane deformation is transformed to out-of-the plane deformation by placing a soft layer on top of it. We demonstrate that the performance of the system is equivalent to the carbon electrode based DEAs in terms of the deformation produced. We also show the capability of the system to be coupled with all kinds of substrates; making it suitable for various applications. The advantage of localized and controlled deformations make it highly useful for applications like Display touchscreens, Tactile touchpads, Buttons on demand and Microfluidic devices.
4:45pm - 5:00pmOral
Development of Portable Sensors Based on Magnetic Levitation
Nanjing Tech University, China
Current sensing technologies usually require expensive and bulky equipments, reliable power, and trained personnel, etc., limiting their applications in resource-limited and point-of-care settings. Magnetic levitation (MagLev) of diamagnetic or weakly paramagnetic materials suspended in a paramagnetic solution in a magnetic ﬁeld gradient provides a simple method to measure the density of small samples of solids or liquids, which is well-suited for producing portable sensors. MagLev can be used for complex, shape-based tasks, such as noncontact, three-dimensional self-assembly, orientation control, and quality control of a wide variety of polymeric components. MagLev can also be used to perform a range of important, density-based bioanalyses. The simplicity-of-use, portability, and low cost of MagLev make it particularly attractive for use in resource-constrained settings (e.g., schools, mines, archeological sites, ﬁeld operations, and laboratories in the developing countries).
5:00pm - 5:15pmOral
All-in-one Self-Powered, Visualized, Visible-Blind and Wearable UV Photodetectors
Jinan University, China
Ultraviolet (UV) radiation shows profound impact on daily health of humankinds, and its detection attracts more and more attention. To meet the growing needs in monitoring health or environment risks, intelligent ultraviolet (UV) photodetectors with special or multiple functions should be explored, such as self-powered or wearable features. Herein, a photoelectrochemical cell (PECC) based self-powered and wearable UV photodetector system with high stability, high speed, as wells as color-indicative ability has been successfully developed. TiO2 nanotubes (NTs) on flexible Ti foil and Prussian blue (PB) on flexible PET/ITO are selected as the photo-anode and electrochromic counter electrode, respectively. By integrating the photosensitive unit and electrochromic display, the fabricated photodetector shows excellent UV responsivity as high as 78.3 mA/W, ultralow UV light detecting limit of 10 μW cm-2, and fast response performance with rise time and decay time of 0.04 s and 0.06 s, respectively. More excitingly, our flexible UV photodetector can not only work stably for 200 cycles of bending but also provide rapid visual recognition of UV exposure by color contrast depth. Our discovery suggests the great potential applications of self-powered smart sensors and wearable healthcare electronics. This study gives an attractive and promising technology for monitoring and managing UV radiation at a personal status.
5:15pm - 5:30pmOral
Wearable Sensor for Biomedical Applications Based on Electrospun Poly(L-lactic Acid) Nanofiber Webs
1Jadavpur University, India; 2University of Wollongong, Australia
Natural or synthetic biodegradable polymers are of great demand nowadays for tissue engineering such as bone healing, nerve repairing, regenerating nitrites in vitro etc. Poly(L-lactic acid) (PLLA) is known as an optically active, biocompatible and degradable polymer that belongs to the group of polymers of poly(glycolic acid) or poly(hydroxybutyric acid) which have wide applications in medicine. Since higher yield of monomer of PLLA is easily been prepared from fermentation of molasses and potato starch thus it is considerably abundant, biocompatable and cost-effective. It has been found that PLLA exhibits unique piezoelectric properties due to its chiral molecular conformation that may open up the enormous possibilities to fabricate biocompatible wearable sensors. A large shear piezoelectric constant of -10 pC/N is exhibited in PLLA because of its polar CO-O group joined to an asymmetric carbon atom.
In this work, we have prepared PLLA nanofibers webs using electrospinning technique and characterized systematically. The piezoelectricity of PLLA nanofiber webs are confirmed by scanning probe microscopy (SPM) based techniques, namely piezoelectric force microscopy and fabricating piezoelectric based wearable pressure sensors. The flexible, lightweight pressure sensor demonstrated the capability of monitoring human physiological signals such as wrist pulse, muscle movement and voice recognition as well. Thus it is indicating that the PLLA nanofiber webs based wearable sensor may extend their potential applications in disease diagnosis that may support the biomedical economy for growing e-health care monitoring.
This work was supported by the Science and Engineering Research Board (SERB/1759/2014-15), Govt. of India. Ayesha Sultana is supported by Maulana Azad National Fellowship (F1-17.1/2015-16/MANF-2015-17-WES-53885/(SA-III/Website)) from UGC. Authors are also thankful for instrumental facilities developed by DST, Govt. of India under FIST-II programme.
 Ikada et al., J. Biomed. Mater. Res., 1996, 30, 553–558.
 Kobayashi et al., J. Appl. Phys., 1995, 77, 2957–2973.
 Fukada et al., Biorheology, 1995, 32, 593–609.
5:30pm - 5:45pmOral
Self-powered Pressure Sensor for Ultra Large Range Pressure Detection
Nanyang Technological University, Singapore
Devices with precise and wide range pressure sensing abilities are of particular importance for the realisation of next-generation sensing technology for potential application in smart and autonomous robotics, sports applications and health-care applications. However, despite extensive research on various kinds of pressure sensors, the major bottleneck is the degradation of sensitivity at higher pressure ranges, thus making it incapable to detect a wide range of pressure with high sensitivity. In this work, we demonstrate a self-powered pressure sensor, capable of detecting a wide range of pressure (0.05 kPa to 600 kPa) by utilising the synergistic effect of piezoelectric polarisation and triboelectric surface charges of the self-polarized Polyvinyldifluoride-trifluoroethylene P(VDF-TrFE) sponge. The self-polarized polymeric sponge fabricated in this work resolves the difficulty of poling porous piezoelectric polymers and eliminate the costly and tedious annealing and poling processes. Considering both the wide pressure range and the sensitivity, this device shows the best performance compared with that of all the self-powered pressure sensors reported so far. This wide sensing range facilitates the use of pressure sensor in broad spectrum of applications, ranging from simple human touch, sensor networks, smart robotics and sports application, thus paving the step forward for the realisation of next-generation sensing devices.
5:45pm - 6:00pmOral
Long-Term Reliability of AlN Platform for MEMS Resonators in Harsh Environments
Institute of Microelectronics, Agency for Science, Technology and Research (A*STAR), Singapore
Long-term reliability of aluminium nitride (AlN)-based MEMS resonators is a primary concern for their deployment in filters, timing devices or as acoustic wave sensors in harsh environments characterized by the regular and huge temperature fluctuation. We investigate the long-term reliability of the fabricated AlN MEMS resonators by conducting a thermal cycling test from −40 °C to 125 °C, in order to simulate accelerated aging of the devices. Two types of devices, namely resonators with an oxide trench array (OTA), and their reference counterparts which do not feature the OTA, are tested. The electrical response of the devices was measured at various interval points. The results reveal that, over 756 cycles, the maximum drift in resonance frequency was < 50 ppm for the Lamb Wave mode. However, for quasi-SAW mode, the drift in resonance frequency was significantly larger for the device with OTA. Reasons for the large frequency drift for devices with OTA are proposed. In particular, the adhesion between the oxide trenches and epitaxial silicon, as well as the uneven residual stress accumulated from thermal cycling, contribute to the large frequency drift. The low temperature (−40 °C) period is especially challenging for the resonator, because the AlN thin film was deposited using chemical vapor deposition at higher temperatures. The above investigation is significant in evaluating the long-term reliability of AlN platform for use in harsh environments.
This work was supported by the Science and Engineering Research Council of Agency for Science, Technology and Research (A*STAR), Singapore, under Grant No. 1423100024.
6:00pm - 6:15pmOral
Design and Development of Ampherometric Sensors using DMFC Technology
Vellore Institute of Technology, India
Ampherometric sensors can be developed for volatile substances like alcohols using Direct Methanol Fuel Cell (DMFC) technology. The objective of this work is to develop low-cost electrocatalyst materials for improved oxygen reduction reaction (ORR) and suitable methods of preparing electrodes that will lead to overall cost reduction of the sensing electrode. Among other Pt alloys, Pt-Sn exhibits high sensitivity in ORR and hence will be used as the ORR catalysts. The current density of the chemically synthesised Pt-Sn/C was analysed for various concentration of methanol at different temperature. This calibration was used in the sensor. The designed and fabrication of the sensor was by means of micro electro mechanical systems (MEMS) technology with the electrochemical inputs using a standard DMFC single cell arrangement. An ampherometric detection technique was employed because of the redox reaction involved and better sensitivity.
To design the sensor we have used a passive mode design protocol in COMSOL Multiphysics. The design and simulation involved optimization of many parameters, in the construction of the cell. The parameters were optimised for a 1.0 cm cell area, interfacing Darcy’s law of fluidic flow through a porous medium, under specific pressure and temperature conditions. The designing involves the construction of gas diffusion layers using carbon matrix for electrodes with various parametric variations. A 3- D printing technique was used to fabricate the cell structure. The output of the cell was optimized for ampherometric detection. MEMS based sensor with microfludic interconnects were fabricated. The sensor response characteristics were studied and will be presented. The response was stable for large number of cycles. The response and sensitivity was temperature dependant. It was found that the cell took a little time to reset. This study shows the feasibility of using DMFC techniques for developing ampherometric sensors for volatile substances like alcohol.