Soft nanocomposite electroadhesives for digital micro- and nanotransfer printing

Abstract

Automated handling of microscale objects is essential for manufacturing of next-generation electronic systems. Yet, mechanical pick-and-place technologies cannot manipulate smaller objects whose surface forces dominate over gravity, and emerging microtransfer printing methods require multidirectional motion, heating, and/or chemical bonding to switch adhesion. We introduce soft nanocomposite electroadhesives (SNEs), comprising sparse forests of dielectric-coated carbon nanotubes (CNTs), which have electrostatically switchable dry adhesion. SNEs exhibit 40-fold lower nominal dry adhesion than typical solids, yet their adhesion is increased >100-fold by applying 30 V to the CNTs. We characterize the scaling of adhesion with surface morphology, dielectric thickness, and applied voltage and demonstrate digital transfer printing of films of Ag nanowires, polymer and metal microparticles, and unpackaged light-emitting diodes.

Advances in laser-assisted mass transfer of MicroLED

“…在巨量转移中, 拾取时需要较强粘附力以保证 拾取可靠； 放置时粘附力则需要尽可能小以实现转移, 因此技术的核心在于提高粘附力切换比. 罗等人 [76] 已经综述了多种用于器件转移的界面调控机理, 如 制备微纳结构 [77] 表面可以实现微弱的粘附力(约为平 整表面的 1/40), 也可通过仿生壁虎纤毛结构 [78] 实现 较强的粘附力(约为平整表面的 12 倍). 在这些方法 中, 激光的快速、局部热传递在界面产生的凸起或微 隆起等起泡结构具备单独可寻址、 较高的粘附切换能 力 , 已 被 广 泛 尝 试 应 用 于 选择性地转移微器件 [27,79,80] [84] .…”

Bioinspired Smart Materials With Externally-Stimulated Switchable Adhesion

“…Compared with other types of external stimuli, electrical modulation has several advantages, including versatility (i.e., no need to modify the adhesive surface), fast actuation, and compatibility with a range of environments (Wan et al, 2019). To achieve switchable adhesion, Kim et al introduced soft nanocomposite electroadhesives, consisting of sparse forests of alumina-coated carbon nanotubes (CNTs) (Figure 6B) (Kim et al, 2019). This bioinspired adhesive can generate electrostatically-modulated switchable dry adhesion, which exhibits 40-fold lower nominal dry adhesion than typical surfaces, yet their adhesive force is enhanced 100 times by applying 30 V to the CNTs.…”

Smart Adhesives via Magnetic Actuation

“…[ 6–11 ] Biologically inspired structures of smart and switchable adhesives have been actively developed to achieve reversibility by applying external stimuli, such as temperature, light, voltage, and mechanical load. [ 12–22 ] Despite advances in artificial adhesives, strategies of effective switches between strong adhesion for object pickup and weak adhesion for object placement are still rare.…”

“…The smart adhesive actuated by voltage generally exhibits a relatively fast response speed. [ 15 ] However, this method does not apply to underwater conditions. Although switchable adhesion of the responsive polymer materials (e.g., shape memory polymers) may be achieved by noncontact external stimuli (temperature and light) in the cases of dry and wet adhesion, the switching process of this kind is generally time costly.…”