The rise of antibiotic resistance as one of the most serious global public health threats has necessitated the timely clinical diagnosis and precise treatment of deadly bacterial infections. To identify which types and doses of antibiotics remain effective for fighting against multi-drug-resistant pathogens, the development of rapid and accurate antibiotic-susceptibility testing (AST) is of primary importance. Conventional methods for AST in well-plate formats with disk diffusion or broth dilution are both labor-intensive and operationally tedious. The microfluidic chip provides a versatile tool for evaluating bacterial AST and resistant behaviors. In this paper, we develop an operationally simple, 3D-printed microfluidic chip for AST which automatically deploys antibiotic concentration gradients and fluorescence intensity-based reporting to ideally reduce the report time for AST to within 5 h. By harnessing a commercially available, digital light processing (DLP) 3D printing method that offers a rapid, high-precision microfluidic chip-manufacturing capability, we design and realize the accurate generation of on-chip antibiotic concentration gradients based on flow resistance and diffusion mechanisms. We further demonstrate the employment of the microfluidic chip for the AST of E. coli to representative clinical antibiotics of three classes: ampicillin, chloramphenicol, and kanamycin. The determined minimum inhibitory concentration values are comparable to those reported by conventional well-plate methods. Our proposed method demonstrates a promising approach for realizing robust, convenient, and automatable AST of clinical bacterial pathogens.

Ionogels have garnered great attention as promising soft conducting materials for the fabrication of flexible energy storage devices, soft actuators, and ionotronics. However, the leakage of the ionic liquids, weak mechanical strength, and poor manufacturability have greatly limited their reliability and applications. Here, we propose a new ionogel synthesis strategy by utilizing granular zwitterionic microparticles to stabilize ionic liquids. The ionic liquids swell the microparticles and physically crosslink microparticles via either electronic interaction or hydrogen bonding. Further introducing a photocurable acrylic monomer enables the fabrication of double-network (DN) ionogels with high stretchability (>600%) and ultrahigh toughness (fracture energy > 10 kJ/m 2 ). The synthesized ionogels exhibit a wide working temperature of −60 to 90 °C. By tuning the crosslinking density of microparticles and physical crosslinking strength of ionogels, we synthesize DN ionogel inks and print them into three-dimensional (3D) motifs. Several ionogel-based ionotronics are 3D printed as demonstrations, including strain gauges, humidity sensors, and ionic skins made of capacitive touch sensor arrays. Via covalently linking ionogels with silicone elastomers, we integrate the ionogel sensors onto pneumatic soft actuators and demonstrate their capacities in sensing large deformation. As our last demonstration, multimaterial direct ink writing is harnessed to fabricate highly stretchable and durable alternating-current electroluminescent devices with arbitrary structures. Our printable granular ionogel ink represents a versatile platform for the future manufacturing of ionotronics.

Soft electronics have attracted enormous attentions in the growing field of bioelectronic integration. Among the various material choices, hydrogels are of particular interest due to their intrinsic similarities with biological tissues. However, challenges still remain for the fabrication of hydrogel electronics, especially those featuring 3D form-factors to conform with the complex biological environment. Here we develop a set of materials which allows for the first time, fully 3D printing of soft electronics featuring soft circuits with arbitrary form factors embedded within soft hydrogel matrix. We design an embedded 3D printing (EM3DP) technology with a curable, ultra-soft (< 5 kPa) and stretchable (λ ~ 18) hydrogel matrix by employing packed hydrogel microparticles possessing a secondary crosslinking capability, and a highly conductive (~1.4×103 S/cm) Ag–hydrogel composite with a segregated conductive network structure. We fabricate various hydrogel-based passive electronics and demonstrate their functionalities. Furthermore, discrete surface-mount components can be readily picked-and-placed at any pre-determined position within the hydrogel matrix and connected with printed passive structures through a highly automated process, thereby greatly expanding the soft electronic functionalities. This work demonstrates the versatility of EM3DP for the future manufacturing of hydrogel-based 3D electronics.