Understanding how light interacts with matter at the nanometre scale is a fundamental issue in optoelectronics and nanophotonics. In particular, many applications (such as bio-sensing, cancer therapy and all-optical signal processing) rely on surface-bound optical excitations in metallic nanoparticles. However, so far no experimental technique has been capable of imaging localized optical excitations with sufficient resolution to reveal their dramatic spatial variation over one single nanoparticle. Here, we present a novel method applied on silver nanotriangles, achieving such resolution by recording maps of plasmons in the near-infrared/visible/ultraviolet domain using electron beams instead of photons. This method relies on the detection of plasmons as resonance peaks in the energy-loss spectra of subnanometre electron beams rastered on nanoparticles of well-defined geometrical parameters. This represents a significant improvement in the spatial resolution with which plasmonic modes can be imaged, and provides a powerful tool in the development of nanometre-level optics.

Mapping surface plasmons on a single metallic nanoparticle

Lightweight, Superelastic, and Hydrophobic Polyimide Nanofiber /MXene Composite Aerogel for Wearable Piezoresistive Sensor and Oil/Water Separation Applications

Smart devices, nowadays, are inspiring the infinite vitality and possibilities of intelligent life, such as self-power electromagnetic (EM) nanogenerator and microsensor, smart window, thermally-driven EM absorber, interstellar energy deliverer, and so on. Herein, the latest and most impressive works of 3D nano-micro architectures and their smart EM devices are highly focused on. The most key information, including assembly strategy and mechanism, EM response, and approach-structure-function relationship, is extracted and well-organized with profundity and easy-to-understand approach. The merit and demerit are revealed by comparison. What's more, the brightest and most cutting-edge smart EM devices constructed by 3D nano-micro architectures are reported as highlights, and the device principles are deeply dissected. Finally, a profound and top comment on the fast-growing field as well as challenges are proposed, and the future directions are predicted intelligently.

Assembling Nano–Microarchitecture for Electromagnetic Absorbers and Smart Devices

Planar circuits for microwaves and lightwaves

With the rapid development and popularization of smart, portable, and wearable flexible electronic devices, urgent demands have been raised for flexible electromagnetic interference (EMI) shielding films to solve related electromagnetic pollution problems. With polyvinyl alcohol (PVA) as polymer matrix, the sandwich-structured EMI shielding nanocomposite films are prepared via electrospinning-laying-hot pressing technology, where Fe3 O4 /PVA composite electrospun nanofibers in the top and bottom layers and Ti3 C2 Tx /PVA composite electrospun nanofibers in the middle layer. Owing to the electrospinning process and the successful construction of the sandwich structure, when the amounts of Ti3 C2 Tx and Fe3 O4 are respectively only 13.3 and 26.7 wt%, the EMI shielding effectiveness (EMI SE) of the sandwich-structured EMI shielding nanocomposite films reach 40 dB with the thickness of 75 µm, higher than that of (Fe3 O4 /Ti3 C2 Tx )/PVA EMI shielding nanocomposite films (21 dB) prepared based on blending-electrospinning-hot pressing process under the same amounts of fillers. Furthermore, the prepared sandwich-structured EMI shielding nanocomposite films possess excellent thermal conductivities and mechanical properties. This novel kind of flexible sandwich-structured EMI shielding nanocomposite films with excellent EMI shielding performances, thermal conductivities, and mechanical properties presents broad application prospects in the fields of EMI shielding and protection for high-power, portable, and wearable flexible electronic devices.

Flexible Sandwich-Structured Electromagnetic Interference Shielding Nanocomposite Films with Excellent Thermal Conductivities.

Reversible Crumpling of 2D Titanium Carbide (MXene) Nanocoatings for Stretchable Electromagnetic Shielding and Wearable Wireless Communication

A novel compact quintuple-mode stub-loaded resonator and ultrawideband (UWB) bandpass filter (BPF) are proposed in this letter. The proposed resonator can generate two odd modes and three even modes in the desired band. The odd-mode resonance frequencies are exclusively correlated to the modified triple-mode resonator; even-mode resonance frequencies can be flexibly controlled by the impedance-stepped open and short stub at its central plane, whereas the odd-mode ones are fixed. The open stubs in pairs at two sides of the low-impedance line are mainly applied to adjust the high resonant modes (fm4, fm5) into desired passband. The short stub can generate two transmission zeros near the lower and upper cutoff frequencies, leading to high rejection skirt. A quintuple-mode UWB filter is simulated, fabricated, and measured. The EM simulated and measured results are presented, and an excellent agreement is obtained.

Compact Quintuple-Mode Stub-Loaded Resonator and UWB Filter

Wireless power transfer (WPT) to the implantable medical devices (IMDs) often suffers from antenna radiation direction and polarization misalignments, which degrades the wireless power link efficiency. Although increasing the incident power density is able to solve the power hunger of IMDs, it poses safety issues to the human tissue. In this paper, an antenna alignment method using intermodulation is proposed to address WPT antenna misalignment in a safe way. Two-tone (2T) waveform excitation is employed to enhance the rectification as well as to generate intermodulation. The intermodulation power is fed back via a magnetic resonant coupling link. Due to the monotonic relation between the intermodulation power and the degree of antenna misalignments, the receiving antenna (in body) can be aligned with the transmitting one (out body). Such a scheme has the advantages of less harm to human tissue and less interference between the 2T waveform excitation and the magnetic resonant coupling link. The whole system is theoretically analyzed and experimentally validated.

Wireless Power Transfer Antenna Alignment Using Intermodulation for Two-Tone Powered Implantable Medical Devices

Metal Ion-Induced Assembly of MXene Aerogels via Biomimetic Microtextures for Electromagnetic Interference Shielding, Capacitive Deionization, and Microsupercapacitors

The RF-to-dc power conversion efficiency (PCE) of the conventional dual-linearly polarized (DLP) rectenna often suffers from uneven RF power received by two ports of the DLP antenna, which is caused by a tilt angle between the linearly polarized incidence and the two polarizations of the antenna. In this letter, a hybrid coupler is employed to redistribute the uneven power from the DLP antenna to two even power distributions for a successive modified Greinacher charge pump (GCP). Thus, a high RF-to-dc PCE of the modified GCP can be maintained. Both theoretical analysis and experiment validate the proposed power distribution scheme, which maintains a stable high PCE of a DLP rectenna irrespective of polarization tilt angle. The proposed scheme is, thus, suitable for high-efficiency wireless power transfer.

Si-Ping Gao

Papers

Reversible Crumpling of 2D Titanium Carbide (MXene) Nanocoatings for Stretchable Electromagnetic Shielding and Wearable Wireless Communication

Compact Quintuple-Mode Stub-Loaded Resonator and UWB Filter

Wireless Power Transfer Antenna Alignment Using Intermodulation for Two-Tone Powered Implantable Medical Devices

Metal Ion-Induced Assembly of MXene Aerogels via Biomimetic Microtextures for Electromagnetic Interference Shielding, Capacitive Deionization, and Microsupercapacitors

Uneven-to-Even Power Distribution for Maintaining High Efficiency of Dual-Linearly Polarized Rectenna