Inertial focusing-based Lab-on-Chip systems represent a promising technology for cell sorting in various applications, thanks to their alignment with the ASSURED criteria recommended by the World Health Organization: Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, and Delivered. Inertial focusing techniques using spiral microchannels offer a rapid, portable, and easy-to-prototype solution for cell sorting. Various microfluidic devices have been investigated in the literature to understand how hydrodynamic forces influence particle focusing in spiral microchannels. This is crucial for the effective prototyping of devices that allow for high-throughput and efficient filtration of particles of different sizes. However, a clear, comprehensive, and organized overview of current research in this area is lacking. This review aims to fill this gap by offering a thorough summary of the existing literature, thereby guiding future experimentation and facilitating the selection of spiral geometries and materials for cell sorting in microchannels. To this end, we begin with a detailed theoretical introduction to the physical mechanisms underlying particle separation in spiral microfluidic channels. We also dedicate a section to the materials and prototyping techniques most commonly used for spiral microchannels, highlighting and discussing their respective advantages and disadvantages. Subsequently, we provide a critical examination of the key details of inertial focusing across various cross-sections (rectangular, trapezoidal, triangular, hybrid) in spiral devices as reported in the literature.

In this study, polymethyl methacrylate (PMMA) is joined with fused silica using pulsed femtosecond laser transmission micro‐welding. This technique enables the welding of transparent materials to each other without the need for intermediate opaque layers, through localized energy deposition. The laser parameters – peak fluence, scanning speed, and hatch distance – are systematically optimized to maximize joint shear strength. The ATR‐FTIR spectroscopic analysis has proven that mechanical interlocking is the primary mechanism of joint formation between the two materials. An analytical model based on heat accumulation is developed to describe the joining process, with a good predictive quality confirmed by comparison with the experimental results. This joining approach is applied to seal a hybrid PMMA‐fused silica microfluidic chip. The device has successfully passed a static leakage test by withstanding pressures up to the full‐scale value of the employed microfluidic pump at 2 bar, demonstrating the effectiveness of femtosecond laser transmission welding for fabricating robust and reliable joints in hybrid microfluidic devices.

The modification of the surface topography at the micro- and nanoscale is a widely established as one of the best ways to engineering the surface of materials, to improve the tribological performances of materials in terms of load capacity and friction. The present paper reviews the state of the art on laser surface texturing by exploiting the technique of direct laser writing for tailoring the coefficient of friction, highlighting the effect of the textures’ arrangement on the lubricated conformal and non-conformal contact behavior.