Superhydrophobic Surface with Controllable Adhesion for Anti‐Roof‐Collapse Application in Flexible Microfluidics

Design of microfluidic reservoir with improved performance is essential in flexible epidermal microfluidic devices, which often suffer from structural instability due to the low stiffness and strong adhesion of the reservoir made of soft elastomers, causing the so-called self-collapse phenomena. Here, a method is proposed to fabricate a flexible superhydrophobic poly(dimethylsiloxane) (PDMS) layer with a low-adhesive surface for epidermal microfluidic device by using chemical etching and soft lithography techniques. The obtained PDMS layer exhibits ultralow dry adhesion with great stability compared to previously made soft layer often having relatively high adhesion. Remarkably, this layer is able to maintain its ultralow adhesion with various counterpart engineering materials even in different environmental conditions, including dry, under water, and under oil conditions, and it exhibits an excellent time durability (more than one month) and use-stability (at least 20 cycles). It is later shown that the designed PDMS layer with ultralow-adhesive and superhydrophobic surface can be applied to prevent the self-collapse of roof effectively in microfluidic reservoir. This study provides an effective design strategy to develop flexible elastomeric materials with controllable adhesion, paving the way for improving the mechanical and structural stability of large dimension reservoirs in wearable microfluidics through surface engineering.