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In combination with higher piezoelectric effect and larger optical second-order susceptibility (χ(2)) compared with aluminum nitride (AlN), scandium-doped aluminum nitride (AlScN) platform is considered as a new platform for future integrated photonics. Hence, further studies are necessary to unlock the potential of the AlScN photonic platform and achieve integrated photonic devices with better performance. In this work, we fabricated the highly c-axis-orientated and low-surface-roughness AlScN thin films by reactive magnetron sputtering with 9.6% and 20% Sc concentrations. Then, we fabricated essential photonic devices including directional coupler (DC), Mach-Zehnder interferometer (MZI), and micro-ring resonator (MRR) based on the AlScN photonic platform. The measured extinction ratios (ERs) of MZIs are 22 dB for Al0.904Sc0.096N and 24 dB for Al0.8Sc0.2N. The maximum quality (Q) factors of MRRs are 3.2×104 for Al0.904Sc0.096N and 2.2×104 for Al0.8Sc0.2N, while the waveguide bending losses are about 6.1 dB/cm for Al0.904Sc0.096N and 10.1 dB/cm for Al0.8Sc0.2N, respectively. These results pave the way towards low-loss integrated AlScN photonic applications such as acousto-optic modulation, nonlinear optical generation.

Noncontact human–machine interactions (HMIs) provide a hygienic and intelligent approach to communicate between humans and machines. However, current noncontact HMIs are generally hampered by the interaction distance, and they lack the adaptability to environmental interference such as high humidity conditions. Here, we explore a self-powered electret-based noncontact sensor (ENS) with moisture-resisting ability and ultrawide sensing range exceeding 2.5 m. A megascopic air-bubble structure is designed to enhance charge-storage stability and charge-recovery ability of the ENS based on the heterocharge-synergy effect in electrets. Besides, multilayer electret films are introduced to strengthen the electric field by utilizing the electrostatic field superposition effect. Thanks to the above improved performances of the ENS, we demonstrate various noncontact HMI applications in harsh environments, including noncontact appliances, a moving trajectory and accidental fall tracking system, and a real-time machine learning-assisted gesture recognition system with accuracy as high as 99.21%. This research expands the way for noncontact sensor design and may further broaden applications in noncontact HMIs.

Filters with narrow bandwidth, high sidelobe suppression ratio (SLSR), and large free spectral range (FSR) play an important role in photonic circuits. In this work, we demonstrate a narrow-band silicon photonic filter using an adiabatic directional coupler (ADC)-assisted subwavelength multimode waveguide Bragg grating (SMWG). The complementary lateral misalignment modulation (CLMM) is applied to realize the apodization for suppressing sidelobes in the filtering spectrum. Two subwavelength corrugations with different widths are designed to achieve a narrow-band filtering spectrum and relieve the requirement of fabrication precision. Experiment results show that a 3-dB bandwidth of 0.51 nm and a SLSR of 16.6 dB are achieved on the CLMM apodized and ADC-assisted SMWG device. An unlimited FSR in the wavelength range of C band is demonstrated as well.

Integrated mid-infrared (MIR) photonics have various applications in optical fiber communication, spectral detection and identification, free-space communication, and light detection and ranging, etc. The MIR electro-optic (EO) modulator, which is one of the key components of MIR integrated photonic systems, has attracted a lot of research interests. In this paper, we review the reported integrated MIR EO modulators based on different modulation mechanisms and material platforms. The recent research progresses and challenges of MIR EO modulators are presented and discussed. The unique advantages and the corresponding applications of each type of MIR modulators are summarized as well. In the end, we provide our perspectives of a few areas in integrated MIR modulators that are worthy for research attention in future.

Non-contact human-machine interaction (HMI) systems that integrate both sensing and feedback capabilities are crucial for smart homes applications. However, the development of non-contact HMI has faced challenges due to its limited interaction scope and potential privacy concerns. Herein, we present an intelligent HMI system where the proposed easy-fabricated electret actuator is integrated with optical ranging technology to facilitate 3D-depth information perception and concurrently convey real-time audio feedback for action reminders. In particular, a broad detection distance exceeding 250cm, accompanied by a detection range of 7.75° scanning angle is achieved. As a proof-of-concept demonstration, the real-time interactions of the recognition of moving object positions integrated seamlessly with audio feedback are presented, thereby providing a thorough evaluation of its potential for HMI in smart homes. Our work offers an effective strategy that broadens the application scenarios of thin film-based HMI systems, paving the way for promising avenues in HMI applications within smart home environments.

A metasurface is a layer of subwavelength-scale nanostructures that can be used to design functional devices in ultrathin form. Various metasurface-based optical devices – coined as flat optics devices – have been realized with distinction performances in research laboratories using electron beam lithography. To make such devices mass producible at low cost, metasurfaces over a large area have also been defined with lithography steppers and scanners, which are commonly used in semiconductor foundries. This work reviews the metasurface process platforms and functional devices fabricated using complementary metal-oxide-semiconductor-compatible mass manufacturing technologies. Taking both fine critical dimension and mass production into account, the platforms developed at the Institute of Microelectronics (IME), A*STAR using advanced 12-inch immersion lithography have been presented with details, including process flow and demonstrated optical functionalities. These developed platforms aim to drive the flat optics from lab to fab.

Metalenses made of artificial sub-wavelength nanostructures have shown the capability of light focusing and imaging with a miniaturized size. Here, we report the demonstration of mass-producible amorphous silicon metalenses on a 12-inch glass wafer via the complementary metal-oxide-semiconductor compatible process. The measured numerical aperture of the fabricated metalens is 0.496 with a focusing spot size of 1.26 μm at the wavelength of 940 nm. The metalens is applied in an imaging system to test the imaging resolution. The minimum bar of the resolution chart with a width of 2.19 μm is clearly observed. Furthermore, the same system demonstrates the imaging of a fingerprint, and proofs the concept of using metalens array to reduce the system size for future compact consumer electronics.

Half-wave plate (HWP) is one of the key polarization controlling devices in optical systems. The conventional HWPs based on birefringent crystals are inherently bulky and difficult to be monolithically integrated with other optical components. In this work, metasurface-based HWPs with high compactness are demonstrated on a 12-inch silicon complementary metal-oxide-semiconductor platform. Three-dimensional finite difference time domain simulation is used to design the nanostructure and investigate the impact of fabrication process variation on the device performance. In addition, the cross- and co-polarization transmittance (Tcrossand Tco) of the HWPs located at different wafer locations are characterized experimentally. The peak Tcrossand valley Tcovalues of 0.69 ± 0.053 and 0.032 ± 0.005 are realized at the wavelength around 1.7 μm, respectively. This corresponds to a polarization conversion efficiency of 95.6% ± 0.8%.

Flexible and wearable devices with the capabilities of both detecting and generating mechanical stimulations are critical for applications in human–machine interfaces, such as augmented reality (AR) and virtual reality (VR). Herein, a flexible patch based on a sandwiched piezoelectret structure is demonstrated to have a high equivalent piezoelectric coefficient of d33at 4050 pC/N to selectively perform either the actuating or sensing function. As an actuator, mechanical vibrations with a peak output force of more than 20 mN have been produced, similar to those from the vibration mode of a modern cell phone, and can be easily sensed by human skin. As a sensor, both the pressure detection limit of 1.84 Pa for sensing resolution and excellent stability of less than 1% variations in 6000 cycles have been achieved. The design principle together with the sensing and driving characteristics can be further developed and extended to other soft matters and flexible devices.

Metasurface-based beam deflector, as an important optical element to bend the light propagation direction, has drawn a lot of interests in research to achieve miniaturization of devices and reduction of system complexity. Based on the 12-inch immersion lithography technology, in this work, an ultra-thin and large-area pixelated metasurface beam deflector with a footprint of 2500 × 2500 μm, formed by nanopillars with diameters from 221 to 396 nm, is demonstrated on a 12-inch glass wafer. The 21 × 21 array of deflectors is designed to bend the input light in different directions and to generate 441 random points. In addition, the layer transfer on the 12-inch glass wafer makes the device working in transmission mode at a 940-nm wavelength. The random point array generated from the experiment shows good match with the design. This pixelated metasurface beam deflector can generate random points simultaneously and has potential to make beam steering by switching each pixel of the beam deflector, which can be applied on motion detection, facial recognition, and light detection and ranging.

Stable and repeatable operation is paramount for practical and extensive applications of all energy harvesters. Herein, we develop a new type of flexible piezoelectret generator, which converts mechanical energy into electricity consistently even under harsh environments. Specifically, the generator, with piezoelectric coefficient (d33) reaching ~ 6300 pC/N, had worked stably for continuous ~ 90000 cycles, and the generator pressed by a human hand produced load peak current and power up to ~ 29.6 μA and ~ 0.444mW, respectively. Moreover, the capability to steadily produce electrical power under extreme moisture and temperature up to 70°C had been achieved for possible applications in wearable devices and flexible electronics.

Wearable healthcare devices with monitoring, treating and protecting applications can provide reliable and newfangled interactive service for people. Herein, a bi-functional smart face mask based on electrospun polyetherimide (PEI) electret nonwoven is developed. By virtue of the surplus charges maintained steadily in the PEI nonwoven, the smart face mask possesses bi-functions of removing the particulate matter and generating electricity. Moreover, the unique applications for dynamically monitoring the particulate matter removal ability and human's respiratory rates are demonstrated. Besides offering an unique air filter, this study will promisingly promote the progress of self-powered wearable electronics.

Flexible device that can harvest renewable energy from environment is urgently needed nowadays. A satisfactory device should be able to harvest multi-type energies around the clock without any economic difficulties for mass production. Here we report an all solution processed flexible hybrid cell by integrating an organic solar cell and triboelectric nanogenerator into a thin film, which is capable to convert both of the solar and mechanical energies into electric power independently or simultaneously, the generated energy can be used either to charge an energy storage unit or as a primary energy source for wearable self-powered devices even in the weak light conditions. This work provides a feasible and scalable method to fabricate the hybrid energy devices within reasonable cost to overcome the environmental restrictions of the devices that the mode of harvest single energy form.

A fiber-based profilometer is developed to measure hard-to-access areas. This system utilizes the low-coherence light interferometry technique to detect the internal surface profiles of some samples. A differentiation method is employed to enhance the lateral and vertical resolutions of the measured imaging results. The probe design parameters are optimized for a desired working distance and a small beam size. The performance of the profilometer system, especially its high-resolution property, is demonstrated.

Self-powered human-interactive but invisible electronics have many applications in anti-theft and anti-fake systems for human society. In this work, for the first time, we demonstrate a transparent paper-based, self-powered, and human-interactive flexible system. The system is based on an electrostatic induction mechanism with no extra power system appended. The self-powered, transparent paper device can be used for a transparent paper-based art anti-theft system in museums or for a smart mapping anti-fake system in precious packaging and documents, by virtue of the advantages of adding/removing freely, having no impairment on the appearance of the protected objects, and being easily mass manufactured. This initial study bridges the transparent nanopaper with a self-powered and human-interactive electronic system, paving the way for the development of smart transparent paper electronics.

Harvesting ambient mechanical energy from human body motion has attracted great research interest. In this work, a power shirt based on triboelectrification and the electrostatic induction effect between fluorinated ethylene propylene (FEP) and external objects is demonstrated. This power shirt can effectively convert the ambient mechanical energy into electric power, and the working mechanism is systematically discussed. A maximum short-circuit current density of ∼0.37 μA/cm2and a maximum peak power density of ∼4.65 μW/cm2were achieved. Simultaneously, 11 blue LEDs were lit by sliding the sleeve and power shirt, indicating the potential application of the power shirt in clothes ornamentation and risk warning. This study develops an efficient path for harvesting human body energy and promoting the development of wearable electronics and smart garments.

A fiber profilometer based on a polarization manipulation technique is developed to measure both surface roughness and profile simultaneously. The depolarization effect caused by the surface scattering is utilized to characterize the roughness properties. A theoretical model is developed to study the second-order dependence of depolarization to quantify the surface roughness characteristics. Experiments are carried out to demonstrate and verify the relationship between the depolarization and the surface roughness. This technique can simultaneously achieve the properties of the surface profile and roughness based on a fiber profilometer system.

Paper-based generator which can be integrated into traditional paper packaging process flows is particularly desirable. In this study, we reported a novel metal-free, non-fluorine, foldable paper-based electret generator based on electrostatic effect. The power generating process was carefully studied by a finite element simulation and numerical calculation in this report. The paper-based generator stimulated by human motion could drive a commercial liquid crystal display (LCD), showing its potential application in anti-counterfeit label. Moreover, a multiple-fold paper-based generator was also fabricated, and the enhancement of the area output is demonstrated. Therefore, the paper-based electret generator can effectively accumulate the irregular energy and extend the applications for paper electronics.

Smart garments for monitoring physiological and biomechanical signals of the human body are key sensors for personalized healthcare. However, they typically require bulky battery packs or have to be plugged into an electric plug in order to operate. Thus, a smart shirt that can extract energy from human body motions to run body-worn healthcare sensors is particularly desirable. Here, we demonstrated a metal-free fiber-based generator (FBG) viaa simple, cost-effective method by using commodity cotton threads, a polytetrafluoroethylene aqueous suspension, and carbon nanotubes as source materials. The FBGs can convert biomechanical motions/vibration energy into electricity utilizing the electrostatic effect with an average output power density of ∼0.1 μW/cm2and have been identified as an effective building element for a power shirt to trigger a wireless body temperature sensor system. Furthermore, the FBG was demonstrated as a self-powered active sensor to quantitatively detect human motion.

Recently, many attempts have been made to increase the specific capacitance of carbon nanotubes (CNTs). Chemical enhancement by adding redox active functional groups on CNTs increases the specific capacitance, while excessive oxidation decreases conductivity and leads to poor cycle life. Here we report the electrochemical enhancement methods followed by annealing at different temperatures in air to add and adjust the redox active functional groups on freestanding CNT films. Functionalized freestanding CNT films were used as positive electrodes, assembled with freestanding CNT/MoO3−xnegative electrodes to fabricate carbon nanotube-based solid-state asymmetric supercapacitors (ASCs). The whole device showed a high volumetric capacitance of 3.0Fcm−3, energy and power density of 1.5mWhcm−3and 4.2Wcm−3, respectively. We also fabricated a SCs pack to drive a homemade wireless transport system successfully, demonstrating the potential applications of this solid-state system for portable/wearable electronics.

Harvest mechanical energy with variable frequency and amplitude in our environment for building self-powered systems is an effective and practically applicable technology to assure the independently and sustainable operation of mobile electronics and sensor networks without the use of a battery or at least with extended life time. In this study, we demonstrated a novel and simple arch-shaped flexible triboelectric nanogenerator (TENG) that can efficiently harvesting irregular mechanical energy. The mechanism of the TENG was intensively discussed and illustrated. The instantaneous output power of single TENG device can reach as high as∼4.125mW by a finger typing, which is high enough to instantaneously drive 50 commercial blue LEDs connected in series, demonstrating the potential application of the TENG for self-powered systems and mobile electronics.

Abstract: A simple (2×2) pixelated flexible infrared nanosensor array based on carbon nanoparticles (CNPs) was fabricated through a simple and low-cost flame method. By integrated with a micro controller unit, the sensor array could detect power density of incident infrared light in real-time. The mechanism for the superior infrared sensing property of the flexible sensor array based on CNP was also studied in detail in this work.