The ability to three-dimensionally interweave biological tissue with functional electronics could enable the creation of bionic organs possessing enhanced functionalities over their human counterparts. Conventional electronic devices are inherently two-dimensional, preventing seamless multidimensional integration with synthetic biology, as the processes and materials are very different. Here, we present a novel strategy for overcoming these difficulties via additive manufacturing of biological cells with structural and nanoparticle derived electronic elements. As a proof of concept, we generated a bionic ear via 3D printing of a cell-seeded hydrogel matrix in the precise anatomic geometry of a human ear, along with an intertwined conducting polymer consisting of infused silver nanoparticles. This allowed for in vitro culturing of cartilage tissue around an inductive coil antenna in the ear, which subsequently enables readout of inductively-coupled signals from cochlea-shaped electrodes. The printed ear exhibits enhanced auditory sensing for radio frequency reception, and complementary left and right ears can listen to stereo audio music. Overall, our approach suggests a means to intricately merge biologic and nanoelectronic functionalities via 3D printing.

Hydrogels such as poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAM-AAc) can be photopatterned to create a wide range of actuatable and self-folding microstructures. Mechanical motion is derived from the large and reversible swelling response of this cross-linked hydrogel in varying thermal or pH environments. This action is facilitated by their network structure and capacity for large strain. However, due to the low modulus of such hydrogels, they have limited gripping ability of relevance to surgical excision or robotic tasks such as pick-and-place. Using experiments and modeling, we design, fabricate, and characterize photopatterned, self-folding functional microgrippers that combine a swellable, photo-cross-linked pNIPAM-AAc soft-hydrogel with a nonswellable and stiff segmented polymer (polypropylene fumarate, PPF). We also show that we can embed iron oxide (Fe2O3) nanoparticles into the porous hydrogel layer, allowing the microgrippers to be responsive and remotely guided using magnetic fields. Using finite element models, we investigate the influence of the thickness and the modulus of both the hydrogel and stiff polymer layers on the self-folding characteristics of the microgrippers. Finally, we illustrate operation and functionality of these polymeric microgrippers for soft robotic and surgical applications.

Shape-changing hydrogels that can bend, twist, or actuate in response to external stimuli are critical to soft robots, programmable matter, and smart medicine. Shape change in hydrogels has been induced by global cues, including temperature, light, or pH. Here we demonstrate that specific DNA molecules can induce 100-fold volumetric hydrogel expansion by successive extension of cross-links. We photopattern up to centimeter-sized gels containing multiple domains that undergo different shape changes in response to different DNA sequences. Experiments and simulations suggest a simple design rule for controlled shape change. Because DNA molecules can be coupled to molecular sensors, amplifiers, and logic circuits, this strategy introduces the possibility of building soft devices that respond to diverse biochemical inputs and autonomously implement chemical control programs.

Self-assembly of millimeter-scale polyhedra, with surfaces patterned with solder dots, wires, and light-emitting diodes, generated electrically functional, three-dimensional networks. The patterns of dots and wires controlled the structure of the networks formed; both parallel and serial connections were generated.

We demonstrate mass-producible, tetherless microgrippers that can be remotely triggered by temperature and chemicals under biologically relevant conditions. The microgrippers use a selfcontained actuation response, obviating the need for external tethers in operation. The grippers can be actuated en masse, even while spatially separated. We used the microgrippers to perform diverse functions, such as picking up a bead on a substrate and the removal of cells from tissue embedded at the end of a capillary (an in vitro biopsy).actuator ͉ biochemical ͉ robotics ͉ thin films B iological function in nature is often achieved by autonomous organisms and cellular components triggered en masse by relatively benign cues, such as small temperature changes and biochemicals. These cues activate a particular response, even among large populations of spatially separated biological components. Chemically triggered activity is also often highly specific and selective in biological machinery. Additionally, mobility of autonomous biological entities, such as pathogens and cells, enables easy passage through narrow conduits and interstitial spaces.As a step toward the construction of autonomous microtools, we describe mass-producible, mobile, thermobiochemically actuated microgrippers. The microgrippers can be remotely actuated when exposed to temperatures Ͼ40°C or selected chemicals. The temperature trigger is in the range experienced by the human body at the onset of a moderate-to-high fever, and the chemical triggers include biologically benign reagents, such as cell media. Using these microgrippers, we achieved a diverse set of functions, such as picking up beads off substrates and removing cells from tissue samples.Conventional microgrippers are usually tethered and actuated by mechanical or electrical signals (1-6). Recently developed actuation mechanisms using pneumatic (7), thermal (8), and electrochemical triggers (9, 10) have also used tethered operation. Because the functional response of currently available microgrippers is usually controlled through external wires or tubes, direct connections need to be made between the gripper and the control unit. These connections restrict device miniaturization and maneuverability. For example, a simple task such as the retrieval of an object from a tube is challenging at the millimeter and submillimeter scale, because tethered microgrippers must be threaded through the tube. Moreover, many of the schemes used to drive actuation in microscale tools use biologically incompatible cues, such as high temperature or nonaqueous media, which limit their utility. There are novel, untethered tools based on shape memory alloys that use low temperature heating, but they have limited mobility and must rely solely on thermal actuation (11,12). The ability of our gripper design to use biochemical actuation, in addition to thermal actuation, represents a paradigm shift in engineering and suggests a strategy for designing mobile microtools that function in a variety of environments with high specif...