In recent years, many kinds of triboelectric nanogenerators (TENG) based on the conjunction of triboelectrification and electrostatic effects have been developed and demonstrated for various energy related applications. Because of its simple structure and facile fabrication craft, TENG can be easily miniaturized to act as a mechanical sensor for detecting vibration, wind speed, location, heart beating, and so forth from various mechanical sources. By leveraging the MEMs technology and flexible materials fabrication processes, we developed various TENGs aiming different medical applications. Technology for enabling drug delivery with precise control is strongly demanded by patients with diabetes or other chronic diseases. More intelligent functions such as drug loading and delivery in controllable manner without requiring electrical power will make low-cost drug delivery patches come true. A smart microneedle patch is developed with the integration of microneedle patch and TENGs for a volume controlled drug delivery triggered by finger pressing. Leveraging triboelectric materials and compatible fabrication technology, we successfully develop a self-powered flexible skin patch for transdermal insulin delivery with novel liquid volume sensor to monitor delivered drug volume and flexible energy harvester using the same triboelectric mechanism. We also explore the feasibility of direct neural stimulation by the output signal from TENGs. With a unique design of water/air triboelectric nanogenerator (WATENG), the charge transfer during the operation of WATENG can be amplified to direct stimulate tibials nerve and peroneal nerve and induce plantar flexion and ankle dorsiflexion. Meanwhile, the WATENG connected with a sling electrode wrapped around the sciatic nerve can also realize a selective stimulation.

Recently, electret-based electrostatic and triboelectric energy harvesting devices have demonstrated their great potential in converting ambient mechanical energy to electrical energy due to their merits of low cost, easy formation and long-term stability. For electret-based generators, the performance of the state-of-the-art MEMS energy harvesters mostly falls into the range of nW or µW level, limiting their potential applications. For triboelectric generators, the output power is severely constrained by the effective surface charge density that only relies on the contact triboelectrification. Herein, we demonstrate a hybrid power generator with folded electrets, which takes the merits of non-contact electrostatic induction by high residue charge within electrets as well as contact triboelectrification by increased surface area. High output power can be readily achieved. Triggered by gentle finger tapping, the instantaneous peak-to-peak output voltage and short-circuit current of up to 1000 V and 0.11 mA have been achieved, which are capable of directly lighting up hundreds of off-the-shelf LEDs. This work pushes forward a significant step of realizing micro electret energy harvesting technologies in real-world applications.

The impact on environment and on health of different pollutants, especially chemical pollutants, is becoming critical due to their drastic consequences on our main vital resource: water. In recent years, extensive efforts of fundamental research and developing practical processes have been devoted to the polluted water treatment. The semiconductor-based photocatalytic process has shown a great potential as an environmental-friendly and sustainable treatment technology due to its low-cost, and its ability to decompose the wide spectrum of contaminants in wastewater at room temperature without residual deposits requiring further post-treatment [1,2]. With high surface/volume ratio, the nanostructured semiconductor shows enhanced photocatalytic efficiency leading to very promising advances in drinking water and wastewater treatment [3,4].

Among the photocatalytic materials, nanostructured ZnO is a promising candidate for its easy-controllable synthesis, its chemical and thermal stability. On the other hand, microfluidic systems can overcome the main limit of the mass transfer during the photo-degradation process of polluted water due to the shorter diffusion lengths within microscale chambers [5]. In this work, we present a high efficiency microfluidic system decorated inside by ZnO nanostructure as a micro-reactor for threes dyes (MB, MO & AR14) as well as for VOCs-polluted water purification.

ZnO nanowire array (NWA) samples have been prepared using two-step hydrothermal method as descripted in our previous work [6]. The SEM images show a quite homogenous NWA with the c-axis preferential growth direction of Wurtzite structure according to the X-ray diffractogram (Fig.1). Fig.2 shows the photodegradation effect of three dyes, it is worth noting that the degradation time is quite long in static mode: after ~3h UV irradiation, the degradation rate (X = (A₀-A/A₀) *100%) reach 86%, 49% and 93% for MB, MO & AR14 respectively. However, by using the micro-reactor with integrated ZnO NWA (Fig. 3), the same degradation efficiency was reached after only 6-7 min photocatalysis process (Fig. 4).

In order to confirm the photocatalysis efficiency of the ZnO-based microfluidics system, an even smaller micro-reactor including a micro-pillar array has been realized. This micro-reactor also co-integrates in-situ grown ZnO nanostructures. The same initial concentration dye-polluted water needs only one-pass (with 250 µL/min flow-rate) to reach quasi total degradation (not shown in the figure). This microfluidic system has also been used to test the VOCs-polluted water purification efficiency. The contaminated water sample contains mixture of six VOC pollutants: Benzene, Toluene, Ethylbenzene and m-p-o Xylenes (BTEX) diluted in water at 10 ppm concentration of each. Fig 6 shows superimposition of two chromatograms before and after one-pass degradation (with 50 µL/min flow-rate). This enables in a selective manner to prove that all VOCs have been dropped below the threshold concentration level of 1 ppm of the maximum allowed contamination level.

We developed a fully automated microflow cytometer for astronauts, which can finish the whole blood preparation and the white blood cell counting automatically. To the best knowledge of the authors, it is the first microflow cytometer designed for space application with automated blood sample preparation function. An enumeration of lymphocyte subsets is carried out and the results show great agreement with the reference commercial flow cytometer.

Seawater desalination is a leading way for tackling the global freshwater shortage challenge. However, existing desalination technologies have their own limits, including high energy consumption or low ion removal capacity, which is not sufficient for desalting high-concentration saline water with low cost. In our recent research efforts, we have designed a new flow-through system with a new concept of dual-ions electrochemical deionization technology, which consists of BiOCl for chloride ion Faradaic electrode on the negative side, sodium manganese oxide (Na_0.44MnO₂) as sodium ion Faradaic electrode on the positive side. It utilizes a redox reaction to individually absorb chloride ions and sodium ions concurrently. Under positive electric current operations, the two ions are released to flow NaCl water electrolyte. Upon switch to negative electric current, the chloride ions are extracted into the negative electrode from flowing NaCl solution while sodium ions are electrochemically captured into the positive electrode. The novel dual-ions Faradaic deionization delivers a stable and reversible salt absorption/desorption capacity of 68.5 mg g^-1 when operated at a current density 100 mA g^-1, which makes over twice salt absorption of the previous reported best performance (31.2 mg g^-1) obtained by a hybrid capacitive deionization system. The electric charge efficiency is up to 0.977 during salt desorption process and 0.958 during absorption process. Owing to ion intercalation process in the salt removal process, energy will be recovered during discharge process. Our research will supply a new method for desalination flow-through system.

Perovskite solar cells (PSCs) have attracted great attention in the scientific community in the past few years. Their many advantages including suitable bandgaps, simple fabrication procedures and outstanding charge-transport properties have propelled PSCs as the promising next-generation photovoltaic systems. However, one key problem faced by PSCs is their short lifetimes that has severely limited their potential for commercialization. The photo-active hybrid inorganic-organic perovskite materials in PSCs were found to degrade rapidly in the air under ambient working conditions. Microscopic understanding of the degradation processes is crucial for the development of more robust perovskite materials. However, such understanding has been limited. In this talk, we discuss the ab initio density-functional study of the degradation reactions of perovskites in the presence of oxygen, water vapor and other reactive molecular species generated from photochemical reactions in the air. We identify the possible degradation mechanisms and examine the different factors affecting the degradation processes. This understanding will provide important guide for rational design of robust perovskite materials for photovoltaic applications.

A 60W nominal power system using a low temperature proton exchange membrane fuel cell (LT-PEMFC) was developed and tested at the Clean Energy Research Centre of Temasek Polytechnic. The power system consists of an ultra-light, open cathode LT-PEMFC stack attached with low power fans as well as a fuel cell control board. The stack comprises of 15 cells with an estimated active area of 8cm2. The stack is designed to operate at a wide range of hydrogen pressure of 0.4bar to 2 bar gauge as opposed to industry standards of 0.3 to 0.6 bar gauge.  The stack is self-humidifying and is able to operate stably with dry hydrogen input. The stack is able to achieve 1W/g peak.

Anode modification with MnO2, Pd and Fe3O4 nanoparticles was evaluated for pharmaceutically active compounds (PhACs) removal and power generation in microbial fuel cells (MFCs). The MFCs with Pd, MnO2 and Fe3O4 anodes achieved a maximum power density of 824, 782 and 728 mW m-2, respectively, which were higher than that with carbon black (CB) modified anode (680 mW m-2) and nonwoven cloth (NW) anode (309 mW m-2). The removal percentages of carbamazepine and diclofenac in MFCs with MnO2, Pd and Fe3O4 anodes were more than 80% and 50%, respectively, while ibuprofen and iohexol showed limited biodegradation. MnO2 and Fe3O4 anodes possessed removal mechanisms of chemical oxidation or reduction and biodegradation. This work for the first time reported the anode modification with MnO2, Pd and Fe3O4to enhance PhACs removal and power generation, which may help to understand the role of metal and metal oxides nanoparticles in the degradation of PhACs and power generation in a bioelectrochemical system. 

Nanowires are often considered to be a core component for the next generation of electronic devices. However, the unique geometry and size-scale of nanowires makes them particularly attractive for discovering and exploring fundamental material properties which are not exclusively inherent to nanowires, but rather are also exhibited in micro- and bulk-specimens. In this work, silicon and other semiconductor nanowires are used a platform for in situ nanomechanical investigations of energy-related materials and applications. The testing of nanowires with our platform can be can be used to determine their basic mechanical properties, such as elastic modulus, fracture strength and creep behavior. Coupled electro-mechanical testing of nanowires can also be employed to confirm stress-induced phase changes in correlated electron materials. Lastly, new investigations and research directions based on the testing platform and methods previously described will be presented.

   Conversion of solar energy into useful fuels using a semiconductor photocatalyst through CO₂ fixation or water splitting has drawn significant attention in recent years due to a growing interest in artificial photosynthesis. Because the main component of sunlight is visible light, the development of a photocatalytic system that efficiently works under visible light is an important subject. In this presentation, recent progress on the development of new photocatalysts that are active for such artificial photosynthetic reactions will be given.

   A hybrid material that consists of a semiconductor and a binuclear metal complex having a redox photosensitizer and a catalytic unit was employed as a photocatalyst for CO₂ reduction under visible light (Fig. 1). This hybrid was capable of reducing CO₂ into HCOOH (or CO) according to two-step photoexcitation of the semiconductor and the photosensitizer unit of the metal complex. It was found that semiconductors of TaON, CaTaO₂N, Y₂Ta₂O₅N₂ and C₃N₄ became active component for this system driven by visible light (> 400 nm) in combination with a suitable binuclear metal complex [1–7].

   We also developed a new photocatalyst consisting of Co(OH)₂ and TiO₂ [8,9]. It is well known that TiO₂ is an active photocatalyst, but only works under UV irradiation. By contrast, the Co(OH)₂/TiO₂ hybrid photocatalyst was capable of absorbing visible light with wavelengths of up to 850 nm and oxidizing water into oxygen gas, even though it consisted of only earth-abundant elements only. To our knowledge, this system provides the first demonstration of a photocatalytic material capable of water oxidation upon excitation by visible light up to such a long wavelength.