Direct 4D printing of functionally graded hydrogel networks for biodegradable,untethered,and multimorphic soft robots

Recent advances in functionally graded additive manufacturing(FGAM)technology have enabled the seamless hybridization of multiple functionalities in a single structure.Soft robotics can become one of the largest beneficiaries of these advances,through the design of a facile four-dimensional(4D)FGAM process that can grant an intelligent stimuli-responsive mechanical functionality to the printed objects.Herein,we present a simple binder jetting approach for the 4D printing of functionally graded porous multi-materials(FGMM)by introducing rationally designed graded multiphase feeder beds.Compositionally graded cross-linking agents gradually form stable porous network structures within aqueous polymer particles,enabling programmable hygroscopic deformation without complex mechanical designs.Furthermore,a systematic bed design incorporating additional functional agents enables a multi-stimuli-responsive and untethered soft robot with stark stimulus selectivity.The biodegradability of the proposed 4D-printed soft robot further ensures the sustainability of our approach,with immediate degradation rates of 96.6%within 72 h.The proposed 4D printing concept for FGMMs can create new opportunities for intelligent and sustainable additive manufacturing in soft robotics.

Aqueous-processable,naphthalene diimide-based polymers for eco-friendly fabrication of high-performance,n-type organic electrolyte-gated transistors

Organic electrolyte-gated transistors(OEGTs) have the benefits of low power consumption and large current modulation.Nevertheless,the electrical performance of n-type OEGTs lags far behind that of p-type OEGTs.In this study,we design a series of polymers,P(NDITEG-T) and P(NDIMTEG-T),comprising a naphthalene diimide backbone for n-type charge transport and oligo(ethylene glycol)(OEG) side chains for high ionic conductivity and eco-friendly solution processing.The incorporation of the OEG chain facilitates the electrochemical doping of the semiconductor by ions to realize high-performance,n-type OEGTs.Notably,in OEGTs,P(NDITEG-T) achieves a high electron mobility of 1.0 × 10^(-1) cm^(2) V^(-1) s^(-1),which represents the highest value reported for solution-processed,n-type OEGTs.It is noted that the fabrication of the OEGTs is achieved by solution processing with eco-friendly ethanol/water mixtures in virtue of the hydrophilic OEG chains.This work demonstrates the molecular design of the P(NDITEG-T) polymer and its significant ability to produce aqueous-processable,high-performance,and n-type OEGTs.