No abstract

Patterning of liquid metal (LM) is usually an integral step toward its practical applications. However, the high surface tension along with surface oxide makes direct patterning of LM very challenging. Existing LM patterning techniques are designed for limited types of planar substrates, which require multiple-step operation, delicate molds and masks, and expensive equipment. In this work, a simple, versatile, and equipment-free approach for direct patterning of LM on various substrates using magnetic field is reported. To achieve this, magnetic microparticles are dispersed into LM by stirring. When a moving magnetic field is applied to the LM droplet, the aggregated magnetic microparticles deform the droplet to a continuous line. In addition, this approach is also applicable to supermetallophobic substrates since the applied magnetic field significantly enhances the contact between LM and substrate. Moreover, remote manipulation of the magnetic microparticles allows direct patterning of LM on nonplanar surfaces, even in a narrow and near closed space, which is impossible for the existing techniques. A few applications are also demonstrated using the proposed technique for flexible electronics and wearable sensors.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adfm.201901370. used for the other liquids. Therefore, it is challenging to directly pattern LM using some well-established printing strategies such as inkjet or screen printing.Various LM patterning techniques have been developed in the past few years based on microfluidic injection, [11] selective wetting, [2d,12] LM suspensions printing, [13] stencil lithography, [14] reductive printing, [15] imprint lithography, [16] selective mechanical sintering, [17] laser patterning, [18] microcontact printing, [19] and three-dimensional (3D) printing. [20] However, the reported techniques involved multiple-step operation, additional pretreatment of substrate, post sintering, delicate molds and masks, tedious microfabrication process, as well as sophisticated equipment. These not only complicated the fabrication but also increased the cost. Besides, each of these reported techniques was designed for a specific substrate, which limited the widespread applications of LM. Due to low adhesion, it is rather difficult to directly pattern LM or transfer the existing LM patterns onto supermetallophobic substrates, on which the contact angle of an LM droplet exceed 150°. In addition, most existing patterning techniques were limited to planar substrates. 3D patterning of LM remains rather challenging, which involved sophisticated facilities (e.g., pressure pump, translation stage) and additional encapsulation and fixation steps for practical applications. [20a] Thus, developing a simple, versatile, and equipment-free LM patterning technique for various planar and nonplanar substrates is highly desired to broaden the applications of LM.It has been reported that magnetic actuation can be used for LM manipu...

An infected skin wound caused by external injury remains a serious challenge in clinical practice. Wound dressings with the properties of antibacterial activity and potent regeneration capacity are highly desirable for wound healing. In this paper, a degradable, ductile, and wound-friendly Zn-MOF encapsulated methacrylated hyaluronic acid (MeHA) microneedles (MNs) array is fabricated through the molding method for promoting wound healing. Due to the damage capability against the bacteria capsule and oxidative stress of the zinc ion released from the Zn-MOF, such MNs array presents excellent antibacterial activity, as well as considerable biocompatibility. Besides, the degradable MNs array composed of photo-crosslinked MeHA possesses the superior capabilities to continuously and steadily release the loaded active ingredients and avoid secondary damage to the wound. Moreover, the low molecular weight hyaluronic acid (HA) generated by hydrolysis of MeHA is also conducive to tissue regeneration. Benefiting from these features, it has been demonstrated that the Zn-MOF encapsulated degradable MNs array can dramatically accelerate epithelial regeneration and neovascularization. These results indicate that the combination of MOFs and degradable MNs array is of great value for promoting wound healing.