AutoSENS: Development of Ultra-Sensitive, Cost-Effective Biosensor for Autonomous Monitoring of Listeria Monocytogenes in Food Industry
Food safety is a major worldwide concern. Every year, contaminated food results in tens of thousands of deaths worldwide. From pathogenic bacteria to toxins, to carcinogenic substances formed in food by heat treatment, every person on this planet is affected by unsafe food, some more than others.
As such, Prof Jorgen Schlundt from CoE’s School of Chemical and Biomedical Engineering and his team of researchers have partnered with international entrepreneurs as well as overseas government agencies like the American FDA via NTU’s Food Technology Centre (NAFTEC) to develop technologies that will assist manufacturers and regulators diagnose important food contaminants in a variety of food products efficiently and rapidly. Specifically, a significant part of the resources are invested on the development of sensors to cheaply and accurately detect highly pathogenic bacteria like Salmonella, Listeria, toxin-producing E. coli, Vibrio vulnificus and Clostridium botulinum.
Additionally, NAFTEC collaborates with international organizations and universities to promote the construction of a comprehensive global genetic database to encompass DNA sequences of all microorganisms. This is a tool that will revolutionize microbiology not only in the food safety area, but also in medical and environmental microbiology and will enable vital future research all around the world.
Assessing and Mitigating Membrane Fouling in Membrane-based Oil-water Separation
Oil-water separations have widespread and economically significant applications in industries spanning from wastewater, oil and gas, food and beverage (F&B), shipping and maritime to metal and machining.
Membrane-based oil-water separations confer many benefits relative to the conventional separation methods like hydrocyclone. Unfortunately, the primary disadvantage of membranes is that fouling (i.e., progressive blocking of the membrane pores) leads to ineffective separation and higher energy costs. Hence, the keys to the technical and economic success of membrane applications in oil-water separations lie in gaining understanding of the mechanisms that give rise to fouling and fouling behavior, and finding an effective method of mitigating fouling. These are also the aims of this research project.
Led by Prof Chew Jia Wei from the School of Chemical & Biomedical Engineering in collaboration with researchers from NTU Nanyang Environment Research & Water Institute, Michigan State University and University of Sydney, the project deploys novel direct observation techniques to obtain a fundamental understanding of the fouling mechanisms, the results of which will be used to develop and validate a model for unravelling the underlying physics of membrane fouling.
Two novel technologies developed in-house will be applied to test the efficacy in oil-water separations. One is targeted at nipping the fouling problem in the bud by preventing the oil foulant from contacting the membrane. The other provides for an energy-efficient means for cleaning the oil that forms on the membrane.
Figure 1. (a) Direct observation of the oil droplets fouling the membrane; (b) Schematic diagram of the novel inverse fluidized bed (IFB) for mitigating membrane fouling; (c) Photo of the carbon fiber aerogel (CFA) for absorbing oil; and (c) photo of the low-density polyethylene (LDPE) foam for absorbing oil
Reversible, Electrocuring Adhesives
Trends in Green Manufacturing and laws mandating recycling have created the need for adhesives that can instantly cure or debond at the touch of a button. Current adhesive technologies do not meet these criteria and are often limited to specific substrates that are stable to high temperatures (thermo-curing) or have visible or transparent surfaces (photo-curing). New adhesives are required to target unmet needs in the fields of polymer electronics and tissue adhesives, for example.
A recent scientific discovery at the PI's laboratory allows adhesive curing by low voltage application, a technology that has never before been commercialised or published in the scientific literature. These 'electrocuring' adhesives may have many competitive advantages over the currently employed on-demand adhesives, as they can be utilised on heat-sensitive materials (e.g. plastics, electronics, soft tissues), can be activated within a few minutes, and require relatively simple circuits for end-user activation. These attributes allow flexible industrial automation, as adhesive application (on a molded part, thin film matrix, etc) and electrocuring are separated into two distinct manufacturing phases without the maintenance-intensive hardware associated with thermo/photo-curing, or 2-part adhesives.
The project led by Asst Prof Terry Steele from the School of Materials Science & Engineering also has experts from University of Oxford, Hebrew University of Jerusalem and University Pierre and Marie Curie.
Figure 1: Electrocuring chemistry for on-demand adhesion. Free radical or carbene precursors are the trigger for cross-linking by applied voltage.
Figure 2: Electro-debonding chemistry for reversible adhesion. Debonding precursors trigger covalent bond scission by low voltages.
Figure 3: Electrocuring adhesive tape allows bonding even to non-conductive substrates by employing interdigitated electrodes.
Figure 4: Inkjet printed silver interdigitated electrodes on polyester films, in collaboration with NRF-CREATE, courtesy of Prof. Schlomo Magdassi.
Figure 5: Real-time material properties of VOLTAGLUE, displaying crosslinking only after activation of -2V. INSET) Screen printed electrodes allow real-time analysis of electrocuring adhesives.
Broadband Plasmonic Devices for Biosensing and Optoelectronic Modulation
The ability of harvesting light and efficiently concentrating its energy into a nanoscale active centre is highly desired for many applications, such as optical biosensing, gas molecule detection, fluorescence, thin-film hotovoltaics, etc.
An efficient light-harvesting process often requires gathering light at the micron scale and concentrating its energy onto a nanoscale hotspot. Subwavelength control of light demands new optical materials, and efforts have turned to metals such as gold and silver, where the plasmon collective excitations of the conduction electrons couple to light and can compress the captured energy into just a few cubic nanometers.
Critical to this harvesting process is an ability to fully characterise and model the plasmonic properties of metallic nanostructures. However, current theoretical studies on this problem are mostly limited to classical electromagnetic methods, which are extremely time-consuming especially when dealing with realistic plasmonic systems, and not accurate when nonlocal effects need to be considered, which presents even more challenges on the design and optimization of nanophotonic devices. Therefore, so far, there is still no general strategy that can be applied to design a series of plasmonic nanodevices with sharp geometrical features and precisely predict their performance, not to mention applying the designs for real-world applications. How to further increase the field enhancements to maximise the efficiency of light mater interactions is still an open question.
Figure 1: Metallic nanoparticles (or particle dimers) with sharp geometrical features or small gaps can harvest light and create huge field enhancement. This field enhancement can be used to generate high harmonic signals
To address this challenge in different nanophotonic applications, Assistant Prof Luo Yu and Prof. Zhang Dao Hua from the School of Electrical and Electronic Engineering in collaboration with Prof Sir John Pendry from Imperial College London, use TO to design efficient plasmonic light-harvesting systems to maximise the enhancement in energy densities, and then probe the nonlocal effects in the optical responses of these devices. The objective is to design and fabricate a feasible plasmonic device that could enhance the field intensity by a factor of 1000, and then apply the designed structure to optical biosesing and ultrafast optoelectronic modulation. The expected outcomes include compact plasmonic sensors with figure of merit comparable to commercialised chemical/bio sensors while maintaining the small size, spectral tunability and adaptability of plasmonic devices, and a low-power-consumption light-controllable plasmonic system for optoelectronic modulation at the femtosecond level. This innovative way of controlling light with a plethora of applications will extend and improve the-state-of-the-art technology in nanoplasmonics and metamaterials, allowing for efficient light harvesting on the nanoscale for biophotonic and optoelectronic applications.
Traffic Safety in Urban Underground Road Systems
- TUM CREATE “Electro-mobility in Megacities: Transportation”
The project led by Prof Wong Yiik Diew of the School of Civil and Environmental Engineering and team in collaboration with PI from TUM-CREATE, assesses the traffic safety impact of urban underground roads. While statistical data on road traffic accidents may be used to quantify traffic safety benefits of urban underground roads, such data are still limited. The project adopts instead a novel approach in evaluating traffic safety based on drivers’ behaviour and perception.
The way drivers follow behind other vehicles on expressways was examined and the findings showed that drivers maintain longer following distances behind other vehicles in an urban road tunnel. Also, the research examined where drivers looked at while driving in an urban road tunnel (see Figures 1 & 2).
Drivers were found to pay more attention to the road ahead of them in an urban road tunnel. A perception study also found drivers to be more safety-oriented in urban road tunnels. Based on these findings, urban road tunnels can be concluded to bring about more traffic safety benefits as compared to conventional open roads.
The holistic assessment and the project outcomes will go to facilitate efforts of transport authorities in their planning of urban underground road systems and road safety.
Figure 1. Eye-tracker used to track where drivers looked at.
Figure 2. Investigating where drivers look at while driving
A Novel Single-Camera Volumetric Flow Measurement Technique Based on Light Field Photography
In this research, Assistant Prof Daniel New of NTU School of Mechanical and Aerospace Engineering collaborates with Associate Prof Shi Shengxian of Shanghai Jiao Tong University to address the experimental complexities and costs associated with the predominant existing technique of measuring 3D fluid flow velocity fields. At present, minimum of four CCD cameras are required to detect small particles that track the flow fields faithfully in order to estimate the actual 3D flow velocity information reconstructed from 2D particle image displacement information captured by each camera. However, due to the high costs of these specialized cameras and challenges in setting up such a system, not too many fluid dynamics research groups have access to this flow measurement technique. Additionally, not all fluid flow scenarios allow the use of so many CCD cameras for flow measurement purposes, due to very limited optical access.
Through the team’s effort, only one high-resolution camera will be used and the trick lies in locating a thin layer of highly precise micro-lens array just before the camera CCD chip. Together with the micro-lens array, the CCD sensor is able to capture 3D light information and thus allows reconstruction of 3D velocity flow information from just one CCD camera. The use of only one single camera allows this technique to be implemented even in flow fields where achieving good optical access is challenging thus increasing the range of fluid flow scenarios that can benefit from this new approach.
Successful outcome of the research will pave the way towards not only a more cost-effective 3D flow measurement technique, but also provides the fluid dynamics research community greater accessibility to a highly-accurate fluid flow measurement tool that is useful not only in fundamental fluid dynamics but also in aerospace engineering, biological engineering, marine engineering and other areas.
Improved Recovery and Energy Efficient Reverse Osmosis (RO) Process
Reverse osmosis (RO) technology is a popular technique for separation, concentration and recovery for various industries. One of the most important applications is the water desalination and reclamation industry. Despite its wide application, RO technology suffers from relatively low recovery (product/feed) and is considered an energy-intensive process. The low recovery (≤ 50%) is mainly due to the high osmotic pressure of the final brine solution that needs to be overcome by the pump. The energy demand for RO technology is caused by factors such as the osmotic pressure, membrane resistance, concentration polarisation, pressure loss in the membrane flow channel and membrane fouling.
This project led by Asst Prof. Chong Tzyy Haur from NTU School of Civil and Environmental Engineering and team members from the School of Mechanical & Aerospace Engineering, University of Hong Kong and University of Colorado, Boulder aims to develop the novel Energy-Efficient Reverse Osmosis (EERO) process to reduce the osmotic penalty, improve the recovery and thus offer energy savings. In the preliminary analysis, the novel EERO process, which consists of conventional Single-Stage RO (SSRO) and a Countercurrent Membrane Cascade with Recycle (CMCR) to further withdraw water from the brine of SSRO, is able to achieve an overall recovery of 75% and requires 12% less energy when compared to conventional SSRO at the same recovery level. Another benefit of having high recovery is that the final concentrated brine can be used for osmotic energy harvesting by a Pressure Retarded Osmosis (PRO) process.
In addition, the project will look at the effect of novel spacers (flow channel devices in the membrane module), fabricated by additive manufacturing (AM) technology, on improving mass transfer in order to reduce concentration polarisation, pressure loss and fouling. This will further reduce the energy demand of an RO process. A design model that includes the membrane module and spacer model will be developed for membrane process optimization. The project is expected to achieve a reduction in energy demand, production costs, chemical use and environmental impact, which are critical to the sustainability of RO technology.
High Thermal Resolution Ultra-Low Power Integrated Imager: Fundamental Design Issues in CMOS
An imager (Figure 1 (a)) can be used to look for hidden objects without physically removing peoples’ clothes or making physical contact. mmW imager has been increasingly used to replace the backscatter X-ray which is potentially more hazardous to health. In terms of deliverable, the analysis, design, fabrication and testing of an ultra-low power fully integrated multiband receiver at millimetre-wave (mmW) with NETD of sub-0.5K and power consumption of 20mW for imaging application will be carried out. Due to the multiband operation and high thermal sensitivity, this imaging receiver will be suitable for rescue effort in low visibility conditions and concealed weapons detection (Figure 1 (b)). Such non-destructive imager can also be adapted for consumer products’ material identification, such as to detect glass shard in a piece of chocolate. The imaging receiver will be implemented in CMOS technology achieving full integration and small die size of <4mm2. The novel and versatile imaging receiver can be launched for mobile application or in remote location. Multi-band frequency design will be incorporated into the input conscious system architecture to optimise NETD. As the power saving through the sub-threshold design and input conscious transceiver are cumulative, a spectacular power consumption reduction of 15 times is achievable.
The research is led by Assistant Professor Boon Chirn Chye, Programme Director of the VIRTUS, IC Design Centre of Excellence in the School of Electrical and Electronic Engineering in collaboration with Assistant Professor Arun Natarajan of Oregon State University.
The Figure 1: (a) Passive mmW full body imager (Pictures from Wikimedia) (b) Atmospheric attenuation under various conditions versus frequency.
Active Control of Turbulent Boundary Layer using Transverse Travelling Waves
All moving vehicles (e.g. aircrafts in air or ship hulls in water) experience drag (resistance force) due to the friction between the surface of the object and the fluid. The energy consumption for transportation is to a large degree devoted to overcoming this resistance. A major part of the contribution to these friction losses is caused by turbulence close to the surface. Turbulence is regarded as one of the most difficult problems of classical physics and even the most fundamental features of the phenomenon is yet to be understood.
The novel idea pursued in this project led by Assistant Professor Martin Skote of the School of Mechanical and Aerospace Engineering in collaboration with Prof Dan Henningson of Royal Institute of Technology (KTH), Sweden, is that the friction drag can be significantly reduced by cross-flow wall motion of the surface. An integrated experimental and computational investigation is undertaken to explore the possibility of applying travelling waves (oscillations in both time and space) as the mode of wall motion for active control of near-wall (boundary layer) turbulence. To fully understand the mechanisms behind the effects of wall oscillations, and optimize the wall motion, fundamental questions regarding near-wall turbulence are addressed.
Figure 1: A horizontal plane taken from the three-dimensional computations. Flow is from left to right. The dark gray indicate low-speed regions and lighter shades indicate high-speed patches. The laminar outflow is equal to the inflow, thus periodic boundary conditions are used in the horizontal plane. The simulation includes transition (from laminar to turbulent flow). The turbulence is greatly reduced by the oscillations which are applied after the turbulence is fully developed. The figure is compressed by a factor five in the downstream (x) direction.
Functional Probiotics as Next-generation Anticancer Dietary Supplements
Glucosinolates, a class of secondary metabolites in plants, have been recognized primarily for their roles in plant defence. Interestingly, a number of studies have shown that cancer risk could be reduced by consumption of glucosinolates-rich cruciferous vegetables such as broccoli, brussels sprout, mustard, and cabbage. To exert the anti-carcinogenic effects, glucosinolates need to be enzymatically converted to isothiocyanates upon consumption. However, the level of bioactive isothiocyanates is often low in blood vessels due to dearth of active myrosinases in digestive tracts.In this project, SCBE Professor Matthew Chang and team together with researchers from the Singapore General Hospital, Duke-NUS Medical School and Lawrence Berkeley National Laboratory of USA aim to develop ‘designer’ probiotics as the next generation health-promoting dietary supplements that stably provide bioactive corresponding enzymes in the gut. Successful outcomes of this project will reduce the risk of cancers through simple diets containing probiotic supplements, which will make a significant contribution to food industries, the scientific community and the public.
A schematic of the project: Consumption of cruciferous vegetables in the presence of our designer probiotics that supply bioactive enzyme will reduce the risk of cancers by increasing level of anticarcinogenic isothiocyanate in the gut.
Smart olfactory MEMS Sensor for Real-time Food Spoilage Detection
Food spoilage is probably one of the biggest problems faced in the daily life. It will ill-affect from creating food shortage to increasing biological waste. Consumers generally follow guidelines on the circulation period set by the food authorities. However, the expiration of “use by” or “best before” dates does not mean that the food is spoiled or objectionable for consumption. The solution is for the food to be fully consumed before its spoliage. However, a safe, cost-effective and highly sensitive smart food spoilage detector has not been effectively developed for commercialisation purpose.
On this premise, Asst Prof Yoon Yong Jin from the School of Mechanical and Aerospace Engineering in collaboration with researchers from NUS and Eastern Regional Research Centre, US Department of Agriculture set out to develop low cost, high sensitivity, and real-time olfactory sensors that can be attached to a variety of food packaging materials including plastic bags, zip-locks or any other air-tight containers to detect food spoilage level. The ultimate goal is to offer a revolutionary and commercially practicable efficient food freshness monitoring system. The work is to identify and quantify the level of food spoilage by food spoilage indicators (FSI), typically ethanol, nitrogen, and organic acids produced by spoilage microorganisms (Figure 1). The major effort of this work is developing “food spoilage detector (FSD)” sensor for detection of food spoilage level. The FSD sensor is a microfluidic sensor that can directly visualise the quantity of FSIs from colour changes on device surface (Figure 2). This FSD sensor is packaged with disposable and patchable stickers for easy implementation on air-tight containers.
Figure.1 Element of the designed gas sensor
Figure 2. Schematic diagram of (a) constitution of the FSD sensor and (b)~(f) sensing mechanism of the FSD sensor