Electroadhesion, i.e., adhesion induced by an electric field, occurs between non-sticky cationic and anionic hydrogels. Here, we demonstrate electroadhesion between cationic gels and animal (bovine) tissues. When gel and tissue are placed under an electric field (DC, 10 V) for 20 s, the pair strongly adhere, and the adhesion persists indefinitely thereafter. Applying the DC field with reversed polarity eliminates the adhesion. Electroadhesion works with the aorta, cornea, lung, and cartilage. We demonstrate the use of electroadhesion to seal cuts or tears in tissues or model anionic gels. Electroadhered gel-patches provide a robust seal over openings in bovine aorta, and a gel sleeve is able to rejoin pieces of a severed gel tube. These studies raise the possibility of using electroadhesion in surgery while obviating the need for sutures. Advantages include the ability to achieve adhesion on-command, and moreover the ability to reverse this adhesion in case of error.

We demonstrate the use of electroadhesion (EA), i.e., adhesion induced by an electric field, to connect a variety of soft materials into 3D structures. EA requires a cationic and an anionic material, but these can be of diverse origin, including covalently cross-linked hydrogels made by polymerizing charged monomers or physical gels/capsules formed by the ionic cross-linking of biopolymers (e.g., alginate and chitosan). Between each cationic/anionic pair, EA is induced rapidly (in ∼10 s) by low voltages (∼10 V DC)and the adhesion is permanent after the field is turned off. The adhesion is strong enough to allow millimeter-scale capsules/gels to be assembled in 3D into robust structures such as capsule–capsule chains, capsule arrays on a base gel, and a 3D cube of capsules. EA-based assembly of spherical building blocks can be done more precisely, rapidly, and easily than by any alternative techniques. Moreover, the adhesion can be reversed (by switching the polarity of the field)hence any errors during assembly can be undone and fixed. EA can also be used for selective sorting of charged soft matterfor example, a ‘finger robot’ can selectively ‘pick up’ capsules of the opposite charge by EA and subsequently ‘drop off’ these structures by reversing the polarity. Overall, our work shows how electric fields can be used to connect soft matter without the need for an adhesive or glue.

Assembling 2D‐material (2DM) nanosheets into micro‐ and macro‐architectures with augmented functionalities requires effective strategies to overcome nanosheet restacking. Conventional assembly approaches involve external binders and/or functionalization, which inevitably sacrifice 2DM's nanoscale properties. Noble metal ions (NMI) are promising ionic crosslinkers, which can simultaneously assemble 2DM nanosheets and induce synergistic properties. Herein, a collection of NMI–2DM complexes are screened and categorized into two sub‐groups. Based on the zeta potentials, two assembly approaches are developed to obtain 1) NMI‐crosslinked 2DM hydrogels/aerogels for heterostructured catalysts and 2) NMI–2DM inks for templated synthesis. First, tetraammineplatinum(II) nitrate (TPtN) serves as an efficient ionic crosslinker to agglomerate various 2DM dispersions. By utilizing micro‐textured assembly platforms, various TPtN–2DM hydrogels are fabricated in a scalable fashion. Afterward, these hydrogels are lyophilized and thermally reduced to synthesize Pt‐decorated 2DM aerogels (Pt@2DM). The Pt@2DM heterostructures demonstrate high, substrate‐dependent catalytic activities and promote different reaction pathways in the hydrogenation of 3‐nitrostyrene. Second, PtCl4 can be incorporated into 2DM dispersions at high NMI molarities to prepare a series of PtCl4–2DM inks with high colloidal stability. By adopting the PtCl4–graphene oxide ink, various Pt micro‐structures with replicated topographies are synthesized with accurate control of grain sizes and porosities.

lysosomes, and peroxisomes in it. [6][7][8][9] Each type of organelle has distinct contents and membrane, which together dictate its unique function within a cell. [8,9] For example, lysosomes have an acidic environment in them that facilitates degradation of proteins. [6] Peroxisomes create an oxidative environment within them, which facilitates the metabolism of lipids. [6,10] Another class of organelles present in plant cells are the chloroplasts, which are involved in capturing energy from sunlight. An important point to note here is that the organelles are chemically "orthogonal" to one another. For instance, the response to sunlight is unique to chloroplasts while degradation under acidic conditions is exclusive to lysosomes. Some of the challenges in designing MCCs (or more broadly, any kind of "artificial cell" or "protocell") are: a) to make these with a prescribed number of compartments; b) to make each compartment distinct in terms of its contents; and c) to achieve unique responses or functions for each compartment. [8,9] The synthesis of MCCs should also ideally be simple, quick, and versatile. All these considerations have guided our approach. [11,12] We have made MCCs using alginate (Alg), an anionic biopolymer that is widely used in biological applications due to its availability, low cost, and ability to form gels/capsules under mild conditions. We developed a water-air microfluidic device to create microscale MCCs, [11] and this ensured that all compartments had an aqueous interior with ambient pH and ionic strength. Using this approach, we were able to address the first two challenges listed above. For example, we reported MCCs with two compartments, each containing a different type of enzyme or nanoparticle. [11] Compared to MCCs prepared from lipids, [13] block copolymers, [1,4] proteins, [14] or multiple emulsions, [15] our Alg-based MCCs are far easier to create. No complex polymers or lipids need to be synthesized, nor is there a need for expensive or time-consuming fabrication techniques.In this study, we enhance the sophistication of our Alg-based MCCs by making the inner compartments "smart," i.e., responsive to various stimuli (Figure 1). Thereby, we address the third challenge above, which is to make the compartments respond distinctly. For this, we endow each compartment with a unique chemical signature by simply using different multivalent cations to crosslink Alg (among Ca 2+ , Fe 3+ , Cu 2+ , etc.) for each compartment. As an example of the final construct, Figure 1 shows an MCC with two compartments. One compartment (C1) alone gets degraded by enzymes from the alginate lyase family. A Eukaryotic cells have inner compartments (organelles), each with distinct properties and functions. One mimic of this architecture, based on biopolymers, is the multicompartment capsule (MCC). Here, MCCs in which the inner compartments are chemically unique and "smart," i.e., responsive to distinct stimuli in an orthogonal manner are created. Specifically, one compartment alone is induced to degrade...