Soft Biomorph Actuators Enabled by Wafer‐Scale Ultrathin 2D PtTe₂ Layers

Abstract

their superior mechanical deformability and ultralightness [8] over their conventional rigid counterparts, which allows for multidegree-of-freedom and high load-toweight ratios. [9] Particularly, soft biomorph actuators have drawn substantial interests, benefiting from their structural simplicity coupled with prominent geometrical adaptivity. [10,11] There are configured by interfacing two different materials of distinct thermal expansion properties; e.g., nonconductive polymers of large mechanical deformability and thin conductive heating layers containing conductive pathways. The mismatch of the coefficient of thermal expansion (CTE) of these constituents generates asymmetric thermal expansion, achieving controlled bending displacements. The conventional approach to fabricate the conductive heating layers is to incorporate electrothermal nanomaterials in dispersed forms into polymer matrices. A variety of conductive nanomaterials that have been so far explored include carbon nanotubes (CNTs), graphene, and silver (Ag) nanowires [11][12][13][14][15][16] which congruently achieve high Joule heating efficiency and large mechanical deformability. However, these solution-based approaches suffer from the uncontrolled integration of randomly dispersed materials with limited spatial homogeneity. As a result, the thickness of the integrated nanomaterials becomes inevitably large (i.e., typically >100 nm) and the polymer/ nanomaterial interfaces are unstable upon repeating actuator operations.Recently, 2D transition metal dichalcogenides (TMDs) have shown great promise in various applications owing to their extraordinary thermal, electrical, optical, and physical properties. [17][18][19] Furthermore, their extremely small thickness allows for an unparalleled level of integration adaptability and conformity to objects with uneven surfaces. [20][21][22] A rich library of 2D TMDs spanning from semiconducting-to-metallic properties [23][24][25] were developed, while earlier focus was on utilizing those with sizeable bandgaps for digital electronics. [26][27][28] Meanwhile, gapless metallic 2D TMD layers are gaining increasing attentions for niche applications demanding a combination of high electrical conductivity and large mechanical deformability. [29][30][31] Platinum ditelluride (PtTe 2 ), an emerging class of metallic 2D TMD layers, demonstrated the highest electrical conductivity ever reported in any 2D TMDs developed so far. [24] 2D PtTe 2 layers exhibit superior electrical-to-thermal conversion Biomorph actuators composed of two layers with asymmetric thermal expansion properties are widely explored owing to their high mechanical adaptability. Electrothermal nanomaterials are employed as the Joule heating components in them for controlled thermal expansion, while their large integration thickness often limits resulting actuation performances. This study reports high-performance ultrathin soft biomorph actuators enabled by near atom-thickness 2D platinum ditelluride (PtTe 2 ) layers-a new class of emergent metallic 2D...

Humidity‐Driven High‐Performance Electrothermal Actuation of Vertically Stacked 2D PtTe2 Layers/Cellulose Nanofibers

“…Especially, soft bimorph actuators composed of heterogeneouslyintegrated functionally distinct layers have received growing attention due to their structural and operational simplicity. [2][3][4] For instance, electrothermal actuations have been demonstrated by utilizing the thermal expansion coefficient (TEC) difference of the active bi-layers, achieving their asymmetric mechanical deformation with electrically driven thermal stimuli. [1,3,4,15] Recently, conductive nanomaterials, such as carbon nanotubes (CNTs), graphene, silver nanowires, and MXenes, have been explored for this approach due to their high electron and phonon transport efficiencies.…”

“…[2][3][4] For instance, electrothermal actuations have been demonstrated by utilizing the thermal expansion coefficient (TEC) difference of the active bi-layers, achieving their asymmetric mechanical deformation with electrically driven thermal stimuli. [1,3,4,15] Recently, conductive nanomaterials, such as carbon nanotubes (CNTs), graphene, silver nanowires, and MXenes, have been explored for this approach due to their high electron and phonon transport efficiencies. [1,4,13,[15][16][17][18][19][20][21][22] However, the resulting actuation proficiency (e.g., bending curvature) is often limited due to their structural inhomogeneity with randomly aligned networks associated with solution-based preparation methods.…”

“…[1,3,4,15] Recently, conductive nanomaterials, such as carbon nanotubes (CNTs), graphene, silver nanowires, and MXenes, have been explored for this approach due to their high electron and phonon transport efficiencies. [1,4,13,[15][16][17][18][19][20][21][22] However, the resulting actuation proficiency (e.g., bending curvature) is often limited due to their structural inhomogeneity with randomly aligned networks associated with solution-based preparation methods. As a result, unstable interface contact of the nanomaterial/polymer cause electrothermal degradation upon repeated biasing.…”

“…Soft actuators enable a variety of applications impossible with traditional actuators and rigid robots owing to their large set of extraordinary characteristics; e.g., superior flexibility, adaptability, compliance, lightweight, as well as multi-degree-of-freedom deformability. [1][2][3][4][5][6][7][8] They respond to a variety of external stimuli such as electricity, heat, light, chemicals, humidity, and biohybrid actuation [1][2][3][4][5][6][9][10][11][12][13][14] in a way to adopt targeted morphologies. Especially, soft bimorph actuators composed of heterogeneouslyintegrated functionally distinct layers have received growing attention due to their structural and operational simplicity.…”

Design of a Dual‐Responsive Bilayered Actuator with Alternating Active Layers

“…Over the past few decades, life phenomena (opening/closing, bending, turning, etc.) activated by external stimuli (light, [1][2][3][4][5] humidity, [6][7][8] temperature, [9][10][11][12] etc.) have attracted more and more attention.…”