Gold nanorods (Au NRs) present unique optical and electronic properties that depend on their morphology. Their applications in sensing and therapeutics require easy synthesis with precise control over their dimensions. Here, we report a method for the synthesis of highly pure and monodisperse Au NRs with fine-tuneable dimensions and longitudinal localised surface plasmon resonance by addition of Hofmeister salts into the growth medium. The control of Au NR formation relies on the double interaction between salt–gold and salt–surfactant (cetyl trimethylammonium bromide, CTAB). With the addition of Hofmeister salts (i.e. NaNO₃, NaBr, NaCl and NaHSO₄) we can fine-tune the aspect ratio of Au NRs in the range of 3.3 to 4.8 with a precision of 0.1 and the longitudinal absorption band from 777 to 960 nm. In addition, we have studied the physical changes in the CTAB micelles induced by the salts using rheology, electron microscopy and light-scattering techniques. We report for the first time cryo-electron microscopy imaging of the micelles under Au NR growth conditions. With the comprehensive characterization of CTAB micelles in the growth solution, this study provides a deeper understanding of the anisotropic growth of metallic crystals.

Since the early 2000s, extensive research has been performed to address numerous challenges in biochip and biosensor fabrication in order to use them for various biomedical applications. These biochips and biosensor devices either integrate biological elements (e.g., DNA, proteins or cells) in the fabrication processes or experience post fabrication of biofunctionalization for different downstream applications, including sensing, diagnostics, drug screening, and therapy. Scalable lithographic techniques that are well established in the semiconductor industry are now being harnessed for large-scale production of such devices, with additional development to meet the demand of precise deposition of various biological elements on device substrates with retained biological activities and precisely specified topography. In this review, the lithographic methods that are capable of large-scale and mass fabrication of biochips and biosensors will be discussed. In particular, those allowing patterning of large areas from 10 cm² to m², maintaining cost effectiveness, high throughput (>100 cm² h^–1), high resolution (from micrometer down to nanometer scale), accuracy, and reproducibility. This review will compare various fabrication technologies and comment on their resolution limit and throughput, and how they can be related to the device performance, including sensitivity, detection limit, reproducibility, and robustness.

Wound healing is a dynamic process with multiple phases. Rapid profiling and quantitative characterization of inflammation and infection remain challenging. We report a paper-like battery-free in situ AI-enabled multiplexed (PETAL) sensor for holistic wound assessment by leveraging deep learning algorithms. This sensor consists of a wax-printed paper panel with five colorimetric sensors for temperature, pH, trimethylamine, uric acid, and moisture. Sensor images captured by a mobile phone were analyzed by neural network–based machine learning algorithms to determine healing status. For ex situ detection via exudates collected from rat perturbed wounds and burn wounds, the PETAL sensor can classify healing versus nonhealing status with an accuracy as high as 97%. With the sensor patches attached on rat burn wound models, in situ monitoring of wound progression or severity is demonstrated. This PETAL sensor allows early warning of adverse events, which could trigger immediate clinical intervention to facilitate wound care management.