A versatile wax assisted double replica molding and its application in flexible electronic skin

Abstract Replica molding is a well-established technique to fabricate surfaces with micro-patterns. Double replica molding of polydimethylsiloxane (PDMS) was developed to fabricate bio-inspired structures though challenged by the cross-linking between PDMS and PDMS. In this paper, we report a novel Wax Assisted Replica Molding (WARM) method to rapidly and precisely copy the microstructures from versatile substrates to PDMS and hydrogels. The low phase transition temperature, hydrophobicity and low surface free energy of wax were utilized to assist transferring patterns from an original master to final replicas. The potential of WARM was demonstrated by generating patters from bio-inspired materials, such as plant leaves and loose fibrous scaffolds, the later was not feasible for direct PDMS replicating. Apart from PDMS, transferring the patterns to materials like hydrogels, sodium alginate, silk fibroin, epoxy glue, and chitosan were also explored. More importantly, the proposed WARM was conducted to fabricate silver nanowire functionalized, microstructure patterned-PDMS specimens, which were further used to construct a flexible electronic skin to monitor human physiological signals, highlighting the potential of WARM in developing biosensors and bioelectronics devices. Neither chemical modification nor special equipment was needed, especially in the favoring of a resource-limited experiment setting.