Dmm6500

A commercial camera (α6300, Sony) was utilized to acquire the optically digital images of the porous structures, the helix structures, and the assembled magnetoelectric devices. The morphological characterization of the TPU powder, NdFeB powder, 316L powder, and surface of the fabricated porous structure was conducted by an environmental scanning electron microscope (ESEM, Quanta 200, FEI, Netherland). The particle sizes and their distributions of the TPU powder, NdFeB powder, and composite powders were measured by a laser particle size analyzer (Mastersizer 3000, Malvern Panalytical, Britain). The magnetic strength on the surface of the porous structure was measured using a WT10A Teslameter (WEITE Magnetic Technology Co., Ltd, China). An electronic dynamic static fatigue testing machine (E1000, Instron‐Division of ITW Limited) was employed to achieve a quantitatively controlled continuous compression/recovery process for magnetoelectric devices and to test the relationship between stress and strain in the cyclic process. The output voltage of integrated 4D printed devices during the compression/recovery process was recorded using a Data acquisition and multimeter system (DMM 6500, Tektronix) with an internal resistance of 1MΩ.

Both uniaxial and biaxial tensile strains were applied using a biaxial tensile testing platform (FlexTest Mini S2-P, Hunan NanoUp Electronics Technology Co., Ltd.). The external pressure was applied and measured by a computer-controlled Z-stage with a force gauge (HP-5N, HandPai). The resistances of sensor units were measured by a digital multimeter (Tektronix DMM6500) with a multichannel scanning module (Tektronix 2000-SCAN). The raw data were recorded in the registers of the digital multimeter and then transmitted to a computer for analysis.

The electrical conductivity of the MME structure was measured by the multimeter (DMM6500, Tektronix Inc, USA). Copper wire electrodes (diameter: 0.25 mm) were attached to the MME structure. For electrical conductivity measurements under cyclic bending, MME coils were printed on polyimide substrates (17 µm in thickness). Cyclic bending of the sample was performed using a custom-made fixture with a controllable bending radius of curvature, stretching an MME fiber with a mechanical testing machine, and measuring the resistance during stretching.

The soft MME robot consists of an electromagnetic generator (EMG) module, a radio frequency (RF) wireless energy transmission module and a triboelectric nanogenerator (TENG) module, a rectifier module, and a boost circuit. As for the EMG module, it consists of two oppositely magnetized MME coils (thickness: 0.8 mm, internal dimensions: 3 × 4 mm², external dimensions: 17 × 18 mm², thread pitch: 0.8 mm, and internal resistance: 2.2 Ω), which are directly printed on the flexible circuit board. Place the designed flexible circuit board at the origin of the printing platform. The MME coils were printed directly on the flexible circuit board. Two lead wires were connected to the MME coils to get the electrical output of EMG. After curing, the soft MME robot was placed horizontally and magnetized by a 3 T pulsed magnetic field. The TENG module consists of two copper coil electrodes (thickness: 0.13 mm, Internal dimensions: 3 × 4 mm², external dimensions: 19 × 20 mm², thread pitch: 0.6 mm, and internal resistance: 1.2 Ω), fluorinated ethylene propylene (FEP) film and polyurethane (PU) film. The output open-circuit voltage (V) and short-circuit current (I) were measured using an electrometer (6514, Keithley, USA) and a multimeter (DMM6500, Tektronix Inc, USA), respectively.