We have discovered that hard, electrical conductors (e.g., metals or graphite) can be adhered to soft, aqueous materials (e.g., hydrogels, fruit, or animal tissue) without the use of an adhesive. The adhesion is induced by a low DC electric field. As an example, when 5 V DC is applied to graphite slabs spanning a tall cylindrical gel of acrylamide (AAm), a strong adhesion develops between the anode (+) and the gel in about 3 min. This adhesion endures after the field is removed, and we term it as hard–soft electroadhesion or EA^[HS]. Depending on the material, adhesion occurs at the anode (+), cathode (−), or both electrodes. In many cases, EA^[HS] can be reversed by reapplying the field with reversed polarity. Adhesion via EA^[HS] to AAm gels follows the electrochemical series: e.g., it occurs with copper, lead, and tin but not nickel, iron, or zinc. We show that EA^[HS] arises via electrochemical reactions that generate chemical bonds between the electrode and the polymers in the gel. EA^[HS] can create new hybrid materials, thus enabling applications in robotics, energy storage, and biomedical implants. Interestingly, EA^[HS] can even be achieved underwater, where typical adhesives cannot be used.

中文翻译：

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将金属和石墨可逆地粘附到水凝胶和组织上

我们发现，硬质电导体（例如金属或石墨）可以粘附到软质水性材料（例如水凝胶、水果或动物组织）上，而无需使用粘合剂。粘附力是由低直流电场引起的。例如，当将 5 V 直流电压施加到横跨丙烯酰胺 (AAm) 高圆柱形凝胶的石墨板上时，阳极 (+) 和凝胶之间会在大约 3 分钟内形成很强的粘附力。这种粘附力在电场移除后仍然存在，我们将其称为硬-软电粘附力或EA ^[HS]。根据材料的不同，粘附发生在阳极 (+)、阴极 (-) 或两个电极处。在许多情况下，可以通过重新施加极性相反的场来反转EA ^{[HS] 。通过}EA ^[HS]与 AAm 凝胶的粘附遵循电化学序列：例如，它发生在铜、铅和锡上，但不会发生在镍、铁或锌上。我们证明EA ^[HS]通过电化学反应产生，在电极和凝胶中的聚合物之间产生化学键。EA ^[HS]可以创造新的混合材料，从而实现机器人、能量存储和生物医学植入物的应用。有趣的是，EA ^[HS]甚至可以在无法使用典型粘合剂的水下实现。