by 2023 the global anticounterfeiting packaging market is projected to reach 208.4 billion USD. [9] The field of anticounterfeiting has a moving target. Initially, for example, almost every country implemented watermarks or fluorescence labels on banknotes to deter copying. [1] Nowadays, a broad range of optical nanomaterials, including metallic nanoparticles, organic dyes, semiconducting quantum dots, and lanthanide-doped nanoparticles (Figure 1) are available to be explored for developing next-generation anticounterfeiting technologies. Thanks to the rapid development of material science, wet-chemistry methods are available for highly controllable synthesis, allowing a large range of nanoparticles with distinguished optical features to be employed as anticounterfeiting taggants. Among them, lanthanide-doped upconversion nanoparticles (UCNPs) are outstanding for the feasibility to tune their optical properties in multiple dimensions. Here, we survey the recent progress in anticounterfeiting applications using new collections of optical nanomaterials as security inks and point out that UCNPs are one of the most promising candidates for high-security-level anticounterfeiting applications. [10] Moreover, we present an outlook for future trends in encryption and decryption devices and technologies toward their real-world adoptions. Nanoparticles for Anticounterfeiting ApplicationsGenerally, anticounterfeiting is done by verifying authentic information that can be either covert or overt. In a typical decoding process, the retrieved information may manifest itself as fluorescence color and intensity in patterns that are varying in the time and space domains. As a crucial element of anticounterfeiting technology, an encoding material serves as a carrier of distinct authentic information. [15] Hence, to achieve a high anticounterfeiting level, the encoding material should be able to offer abundant optical states that can be tailored to carry unique information. In this regard, nanoparticle materials (Table 1) have attracted tremendous interest owing to their exceptional stability, controllability, and diversity in tuning their optical properties in multiple dimensions, e.g., fluorescence color, intensity, and lifetime value. We surveyed and summarized several key fundamental optical features including reflection, absorption, scattering, and fluorescence that can be Optical nanomaterials have been widely used in anticounterfeiting applications. There have been significant developments powered by recent advances in material science, printing technologies, and the availability of smartphone-based decoding technology. Recent progress in this field is surveyed, including the availability of optical reflection, absorption, scattering, and luminescent nanoparticles. It is demonstrated that advances in the design and synthesis of lanthanide-doped upconversion nanoparticles will lead to the next generation of anticounterfeiting technologies. Their tunable optical properties and optical responses to a range of external stimuli a...

The first highly stretchable and sensitive spin valve sensor on elastomeric membranes are demonstrated. The sensor elements exhibit stable GMR behavior up to tensile strains of 29% in in situ stretching experiments and show no fatigue over 500 loading cycles. This remarkable stretchability is achieved by a predetermined periodic fracture mechanism that creates a meander-like pattern upon stretching.

Thermally responsive fluorescent nanoparticles can be constructed to allow robust, rapid, and noninvasive temperature measurements. Furthermore, due to their tiny size, they can be used to detect temperature changes at the nanoscale. In this way, such sensors are ideally suited to emerging applications including intracellular temperature sensing and microelectronics failure diagnostics. Despite their potential, current nanothermometers still suffer from limited sensitivity, dynamic range, and stability. By introducing thermal enhanced anti-Stokes emission from a pair of lanthanide ions, ytterbium and neodymium, we show an increase of more than 1 order of magnitude in both the sensitivity and the dynamic range when compared to conventional ytterbium and erbium-codoped nanothermometers. Here, we report heterogeneous temperature-responsive nanoparticles with a new record of sensitivity (9.6%/K at room temperature and above 2.3%/K at elevated temperatures up to 413 K) that can be used for ratiometric thermometry. The heterogeneous nanostructure design shows that the thermal responses can be fine-tuned by the controlled growth of nanoparticles. The stability of the ultrasensitive nanothermometers has enabled long-term noncontact monitoring of local heat dissipation of a microelectronic device.

Detection and quantification of a variety of micro- and nanoscale entities, e.g. molecules, cells, and particles, are crucial components of modern biomedical research, in which biosensing platform technologies play a vital role. Confronted with the drastic global demographic changes, future biomedical research entails continuous development of new-generation biosensing platforms targeting even lower costs, more compactness, and higher throughput, sensitivity and selectivity. Among a wide choice of fundamental biosensing principles, magnetic sensing technologies enabled by magnetic field sensors and magnetic particles offer attractive advantages. The key features of a magnetic sensing format include the use of commercially available magnetic field sensing elements, e.g. magnetoresistive sensors which bear huge potential for compact integration, a magnetic field sensing mechanism which is free from interference by complex biomedical samples, and an additional degree of freedom for the on-chip handling of biochemical species rendered by magnetic labels. In this review, we highlight the historical basis, routes, recent advances and applications of magnetic biosensing platform technologies based on magnetoresistive sensors.