Transfer printing, as an important assembly technique, has attracted much attention due to its valuable merits to develop novel forms of electronics such as stretchable inorganic electronics requiring the heterogeneous integration of inorganic materials with soft elastomers. Here, we report on a laser-driven programmable non-contact transfer printing technique via a simple yet robust design of active elastomeric microstructured stamp that features cavities filled with air and embedded under the contacting surface, a micro-patterned surface membrane that encapsulates the air cavities and a metal layer on the inner-cavity surfaces serving as the laser-absorbing layer. The micro-patterned surface membrane can be inflated dynamically to control the interfacial adhesion, which can be switched from strong state to weak state by more than three orders of magnitude by local laser heating of the air in the cavity with a temperature increase below 100°C. Theoretical and experimental studies reveal the fundamental aspects of the design and fabrication of the active elastomeric microstructured stamp and the operation of non-contact transfer printing. Demonstrations in the programmable transfer printing of micro-scale silicon platelets and micro-scale LED chips onto various challenging receivers illustrate the extraordinary capabilities for deterministic assembly that are difficult to address by existing printing schemes, thereby creating engineering opportunities in areas requiring the heterogeneous integration of diverse materials such as curvilinear electronics and MicroLED displays.
Octopus suckers offer remarkable adhesion performance against nonporous surfaces and have inspired extensive research to develop artificial adhesives. However, most of existing octopus‐inspired adhesives are either passive without an actuation strategy or active but not energy efficient. Here, a novel design of a magnetically actuated, energy‐efficient smart adhesive with rapidly tunable, great switchable, and highly reversible adhesion strength inspired by the elastic energy storage mechanism in octopus suckers is reported. The smart adhesive features two cavities separated by an elastic membrane with the upper cavity filled with magnetic particles while the lower one empty. The deformation of the elastic membrane can be actively controlled by an external magnetic field to change the cavity volume, thus generating a cavity‐pressure‐induced adhesion. Systematically experimental and theoretical studies reveal the fundamental aspects of design and operation of the smart adhesive and give insights into the underlying adhesion mechanisms. Demonstrations of this smart adhesive in transfer printing and manipulation of various surfaces in both dry and wet environments illustrate the potential for deterministic assembly and industrial or robotic manipulation.
Transfer printing based on switchable adhesive that heterogeneously integrates materials is essential to develop novel electronic systems, such as flexible electronics and micro LED displays. Here, we report a robust design of a thermal actuated switchable dry adhesive, which features a stiff sphere embedded in a thermally responsive shape memory polymer (SMP) substrate and encapsulated by an elastomeric membrane. This construct bypasses the unfavorable micro- and nano-fabrication processes and yields an adhesion switchability of over 1000 by combining the peel-rate dependent effect of the elastomeric membrane and the thermal actuation of the sub-surface embedded stiff sphere. Experimental and numerical studies reveal the underlying thermal actuated mechanism and provide insights into the design and operation of the switchable adhesive. Demonstrations of this concept in stamps for transfer printing of fragile objects, such as silicon wafers, silicon chips, and inorganic micro-LED chips, onto challenging non-adhesive surfaces illustrate its potential in heterogeneous material integration applications, such as flexible electronics manufacturing and deterministic assembly.
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