Here, we report advanced materials and devices that enable highefficiency mechanical-to-electrical energy conversion from the natural contractile and relaxation motions of the heart, lung, and diaphragm, demonstrated in several different animal models, each of which has organs with sizes that approach human scales. A cointegrated collection of such energy-harvesting elements with rectifiers and microbatteries provides an entire flexible system, capable of viable integration with the beating heart via medical sutures and operation with efficiencies of ∼2%. Additional experiments, computational models, and results in multilayer configurations capture the key behaviors, illuminate essential design aspects, and offer sufficient power outputs for operation of pacemakers, with or without battery assist.biomedical implants | flexible electronics | transfer printing | wearable electronics | heterogeneous integration N early all classes of active wearable and implantable biomedical devices rely on some form of battery power for operation. Heart rate monitors, pacemakers, implantable cardioverterdefibrillators, and neural stimulators together represent a broad subset of bioelectronic devices that provide continuous diagnostics and therapy in this mode. Although advances in battery technology have led to substantial reductions in overall sizes and increases in storage capacities, operational lifetimes remain limited, rarely exceeding a few days for wearable devices and a few years for implants. Surgical procedures to replace the depleted batteries of implantable devices are thus essential, exposing patients to health risks, heightened morbidity, and even potential mortality. The health burden and costs are substantial, and thus motivate efforts to eliminate batteries altogether, or to extend their lifetimes in a significant way.Investigations into energy-harvesting strategies to replace batteries demonstrate several unusual ways to extract power from chemical, mechanical, electrical, and thermal processes in the human body (1, 2). Examples include use of glucose oxidation (3), electric potentials of the inner ear (4), mechanical movements of limbs, and natural vibrations of internal organs (5-7). Such phenomena provide promising opportunities for power supply to wearable and implantable devices (6-8). A recent example involves a hybrid kinetic device integrated with the heart for applications with pacemakers (7). More speculative approaches, based on analytical models of harvesting from pressure-driven deformations of an artery by magneto-hydrodynamics, also exist (9).Cardiac and lung motions, in particular, serve as inexhaustible sources of energy during the lifespan of a patient. Mechanicalto-electrical transduction mechanisms in piezoelectric materials offer viable routes to energy harvesting in such cases, as demonstrated and analyzed by several groups recently (10-17). For example, proposals exist for devices that convert heartbeat vibrations into electrical energy using resonantly coupled motions of thick (1-2 mm) pi...

Mutualistic intracellular symbiosis between bacteria and insects is a widespread phenomenon that has contributed to the global success of insects. The symbionts, by provisioning nutrients lacking from diets, allow various insects to occupy or dominate ecological niches that might otherwise be unavailable. One such insect is the glassy-winged sharpshooter (Homalodisca coagulata), which feeds on xylem fluid, a diet exceptionally poor in organic nutrients. Phylogenetic studies based on rRNA have shown two types of bacterial symbionts to be coevolving with sharpshooters: the gamma-proteobacterium Baumannia cicadellinicola and the Bacteroidetes species Sulcia muelleri. We report here the sequencing and analysis of the 686,192–base pair genome of B. cicadellinicola and approximately 150 kilobase pairs of the small genome of S. muelleri, both isolated from H. coagulata. Our study, which to our knowledge is the first genomic analysis of an obligate symbiosis involving multiple partners, suggests striking complementarity in the biosynthetic capabilities of the two symbionts: B. cicadellinicola devotes a substantial portion of its genome to the biosynthesis of vitamins and cofactors required by animals and lacks most amino acid biosynthetic pathways, whereas S. muelleri apparently produces most or all of the essential amino acids needed by its host. This finding, along with other results of our genome analysis, suggests the existence of metabolic codependency among the two unrelated endosymbionts and their insect host. This dual symbiosis provides a model case for studying correlated genome evolution and genome reduction involving multiple organisms in an intimate, obligate mutualistic relationship. In addition, our analysis provides insight for the first time into the differences in symbionts between insects (e.g., aphids) that feed on phloem versus those like H. coagulata that feed on xylem. Finally, the genomes of these two symbionts provide potential targets for controlling plant pathogens such as Xylella fastidiosa, a major agroeconomic problem, for which H. coagulata and other sharpshooters serve as vectors of transmission.

Several insect groups have obligate, vertically transmitted bacterial symbionts that provision hosts with nutrients that are limiting in the diet. Some of these bacteria have been shown to descend from ancient infections. Here we show that the large group of related insects including cicadas, leafhoppers, treehoppers, spittlebugs, and planthoppers host a distinct clade of bacterial symbionts. This newly described symbiont lineage belongs to the phylum Bacteroidetes. Analyses of 16S rRNA genes indicate that the symbiont phylogeny is completely congruent with the phylogeny of insect hosts as currently known. These results support the ancient acquisition of a symbiont by a shared ancestor of these insects, dating the original infection to at least 260 million years ago. As visualized in a species of spittlebug (Cercopoidea) and in a species of sharpshooter (Cicadellinae), the symbionts have extraordinarily large cells with an elongate shape, often more than 30 m in length; in situ hybridizations verify that these correspond to the phylum Bacteroidetes. "Candidatus Sulcia muelleri" is proposed as the name of the new symbiont.

Mechanical assessment of soft biological tissues and organs has broad relevance in clinical diagnosis and treatment of disease. Existing characterization methods are invasive, lack microscale spatial resolution, and are tailored only for specific regions of the body under quasi-static conditions. Here, we develop conformal and piezoelectric devices that enable in vivo measurements of soft tissue viscoelasticity in the near-surface regions of the epidermis. These systems achieve conformal contact with the underlying complex topography and texture of the targeted skin, as well as other organ surfaces, under both quasi-static and dynamic conditions. Experimental and theoretical characterization of the responses of piezoelectric actuator-sensor pairs laminated on a variety of soft biological tissues and organ systems in animal models provide information on the operation of the devices. Studies on human subjects establish the clinical significance of these devices for rapid and non-invasive characterization of skin mechanical properties.