Xin Chen's research while affiliated with Harvard University and other places

... 37 Na + ions tend to screen the negative charges on polyelectrolytes, which eventually reduces the stretching of polymer chains. 38,39 Moreover, the effect of divalent ions on the viscosity of polymer solutions is much higher than that of monovalent ions; divalent ions can associate along the polymer back bone to form intrachain pairs and a manning condensation, in which a polymer behaves like a tight coil, is obtained. 40 Despite the vital importance for salinity effect on polymer systems, previous studies (experimental or theoretical) focused on either steady shear or oscillatory shear 41−44 properties and limited information is available for extensional flow behavior. ...

... In this way, various soft actuators with conical [4,5], tapered [6,7], planar [8,9], and doubly curved shell [10] shapes have been developed to perform continuous movements and operate in harsh environments. Recently, cylindrical shapes formed by bellows structures or origami methods have also been proposed [11,12]. Cylindrical shapes can be utilized in the manufacturing of medical devices and biomimetic robots because the shapes ensure that contact with the external environment is minimized, unlike in the case of prismatic shapes, and these shapes can more easily pass through narrow gaps [13][14][15][16]. ...

... Comparatively, SSA has a sizeable capturing surface and great environmental adaptability. Some of the developed SSAs are pneumatically operated soft wearable gloves [18], starfish-inspired soft robots for grasping soft or fragile objects [19], and soft grippers for adjustable grasping [20,21]. As SSAs exhibit larger deflection, adaptability in grasping, and fast response speed, they have a great future in industrial applications. ...

... 21,22 Previous results by Xu et al. and our team have demonstrated the electron-transfer dominant mechanism in metal/dielectric CE. 20,[23][24][25] Such the electron-transfer mechanism was also proposed and demonstrated by multiple previous studies. In the meanwhile, some researchers insist mass transfer exists in CE. [26][27][28][29][30][31] Especially, the mosaic of surface charge discovered by Grzybowski et al. 32 and the thermionic emission behaviors discovered by us 20 indicated the existence of the bidirectional mass transfer in polymer/ polymer CE. However, the quantitative model to describe the contributions from different mechanisms under diverse material systems is still lacking. ...

... However, at this stage, the neck undergoes a slow thinning process. This is due to the time-dependent straining behavior of the viscoelastic 48 PDMS, which results in the viscoelastic thinning of the PDMS neck. Finally, the neck thins beyond a critical thickness, separating the wrapped core drop from the interfacial layer (timestamps, t ∼ 171 ms for We i = 261 and t ∼ 146 ms for We i = 214). ...

... Among these are fluidic elastomer actuators (FEA), hydraulic and pneumatic systems which pressurize inner networks of chambers within the soft material they are driving [42,43]. Most common in this approach are pneunets [44][45][46][47][48][49] (pictured in Fig. 1d), which are frequently used to enable crawling locomotion [46,[50][51][52] as well as grasping and manipulation [22, [53][54][55]. Similar in concept, origami structures such as the one in Fig. 1e, which unfold and collapse in response to pneumatic input, are increasingly common in the field [23, [56][57][58]. ...

... The available numerical, experimental, and analytical studies in the literature mainly focus on the droplet motion in linear sequences, known as single lane flows, in relatively simple channels, such as, simple loops, cascaded loops or sizeable regular grid of short channels, resembling porous materials. [17][18][19][20][21][22] In contrast, very few studies have been found to deal with the navigation of bubbles through a complex microfluidic network. Choi et al. 17 described the behavior of bubble/s suspended in the carrier fluid and flowing through microfluidic networks.They reported that a bubble moves by interacting with the carrier fluid around it, increases the channel resistance it occupies, and always chooses a path with the least hydrodynamic resistance. ...

... Furthermore, the mechanical properties of hydrogels pose limitations on the maximum actuation force that can be generated, in contrast to elastomer matrices such as Ecoflex, Elastosil, and Sylgard 184. 146,147 However, the inherent versatility and tunable physical/chemical properties of hydrogels make them promising candidates for designing actuators driven by pneumatic and hydraulic pressure. These features facilitate easy functionality and enable the development of tailored actuation systems. ...

... In addition, the micropyramid structure has great potential in microelectronic devices such as transistors, semiconductor chips, and sensors [12][13][14]. In order to apply this kind of nanostructure to other materials, many nanomechanical technologies have been developed, such as soft imprinting, selfassembly, nanoimprinting, electron beam etching, and so on [15][16][17][18]. However, most of the current works are mainly focused on the fabrication of pyramid Si, which limited the application field. ...

... Micro-PADs are being developed using methods that involve cutting hydrophilic channels in paper so that fluids can flow through them by capillary action [8]. Disposable systems utilizing wax as a hydrophobic barrier have seen widespread use for a variety of applications, including the measurement of total proteins, cholesterol, glucose, and harmful drugs in biological fluids [9] and the sensing of heavy metal ions in a water matrix [10]. The substrate of paper is naturally hydrophilic, and in order to contain fluid flow in specific area or guide fluidics along a predetermined path, the creation of a hydrophobic barrier is necessary. ...