The strategy of engineering the local chemical environment to direct selectivity in the electroreduction of CO2 toward value-added products is only qualitatively understood. The unfeasibility of local concentration measurements and the limited applicability of simulations to practical systems hinder more precise guidelines. Herein, we quantify the impact of the (electro)chemical environment on the selectivity pattern using microstructured Cu electrodes prepared by ultrashort pulse laser ablation. We created regularly distributed micro-probes and assessed their product distributions at distinct overpotentials. The regular geometry enabled the accurate simulation of the local pH and CO2 concentration. Selectivity maps useful for mechanistic and applied studies emerged. They reveal clear patterns for C1-C3 products suggesting novel insights such as the presence of two reaction mechanisms for propanol. The effect on the selectivity pattern of operation parameters such as enhanced mass transport and electrolyte composition was also predicted by the maps.

Liquid transport (continuous or segmented) in microfluidic platforms typically requires pumping devices or external fields working collaboratively with special fluid properties to enable fluid motion. Natural liquid adhesion on surfaces deters motion and promotes the possibility of liquid or surface contamination. Despite progress, significant advancements are needed before devices for passive liquid propulsion, without the input of external energy and unwanted contamination, become a reality in applications. Here we present an unexplored and facile approach based on the Laplace pressure imbalance, manifesting itself through targeted track texturing, driving passively droplet motion, while maintaining the limited contact of the Cassie–Baxter state on superhydrophobic surfaces. The track topography resembles out-of-plane, backgammon-board, slowly converging microridges decorated with nanotexturing. This design naturally deforms asymmetrically the menisci formed at the bottom of a droplet contacting such tracks and causes a Laplace pressure imbalance that drives droplet motion. We investigate this effect over a range of opening track angles and develop a model to explain and quantify the underlying mechanism of droplet self-propulsion. We further implement the developed topography for applications relevant to microfluidic platform functionalities. We demonstrate control of the rebound angle of vertically impacting droplets, achieve horizontal self-transport to distances up to 65 times the droplet diameter, show significant uphill motion against gravity, and illustrate a self-driven droplet-merging process.

A novel approach for machining of cylindrical hard materials and arbitrary shapes is presented. Alumina-toughened zirconia dental implants with complex geometry are manufactured with femtosecond quasi-tangential laser ablation. This rapid prototyping approach for small-scale production decreases the development-time cycle tremendously and trumps conventional approaches. Moreover, a competitive parameter study for radial and tangential ablation with single and multi-pulse is presented. A process achieving an ablation rate of 1 mm 3 min −1 with a surface roughness R a of 0.2 µm is introduced. The meta-stable tetragonal phase of the ceramic persists and is assessed via Raman spectroscopy. The small heat-affected zone is subsequently ablated with a radial laser process step. Hence, high-precision dental implants with a mean error of smaller 5 µm over the complete contour are shown.

Surface structuring is a versatile tool to modify the physical interplay at the interface to gaseous or liquid media. The two industrial used approaches are, in general, a chemical modification via coating or/and an introduced topography. Here, the structuring is carried out with a direct technique using an ultrashort pulsed laser with infrared and green wavelengths. Two hierarchical structural units are generated at the surface on copper, aluminum, and an amorphous alloy. Structures in the micrometer regime are produced via 2.5D layered laser ablation. Laser induced periodic surface structures (LIPSSs), an inherent phenomenon of self-generated periodic features, can be utilized to generate subdiffraction limit features. LIPSSs are demonstrated in the high spatial frequency regime with a periodicity of 320 and 600 nm for green and infrared radiations, accordingly. This work concerns the use of direct laser structuring for potential applications. Specifically, a change in the optical and wetting properties is addressed. Broadband absorbing behavior and static contact angles of up to 152° are reported. Laser ablation processes and experimental routines are presented to upscale the structuring process. Production rates up to 100 mm2/h for 2.5D ablation and 0.6 m2/h for LIPSSs can be reached.

Diamond is a wide bandgap material, which exhibits an abrupt increase of its free-electron density, when excited by an ultrashort laser pulse. The generation of free electrons transforms the insulator diamond to a conducting material with metallic optical behavior. This transformation process can be described by the multiple rate equation (MRE) model. The introduced MRE model considers strong-field excitation in the Keldysh picture as well as collisional excitation. The light attenuation results from the strong-field absorption and free-carrier absorption described in the Drude picture. Thus, the electron density and intensity distribution as functions of time, penetration depth, and laser beam radius are calculated. Furthermore, the model predicts the evolution of optical properties and estimates the ablation threshold value by the diameter and depth regression method. The calculated ablation threshold is compared to experimental results on a single crystalline chemical vapor deposited diamond by applying the diameter and depth regression method. Experimental and theoretical results are discussed with regard to the pulse duration. The discussion focuses on single pulse ablation but also addresses the multishot domain, which is essential for laser machining. At 1030 nm, the experimental single pulse ablation threshold fluence is determined to be 8.2 and 12.9 J/cm2 for pulse durations of 400 and 700 fs, respectively. This is in compliance with the simulation results.