Electronics that are capable of intimate, non-invasive integration with the soft, curvilinear surfaces of biological tissues offer important opportunities for diagnosing and treating disease and for improving brain-machine interfaces. This paper describes a material strategy for a type of biointerfaced system that relies on ultrathin electronics supported by bioresorbable substrates of silk fibroin. Mounting such devices on tissue and then allowing the silk to dissolve and resorb initiates a spontaneous, conformal wrapping process driven by capillary forces at the biotic/abiotic interface. Specialized mesh designs and ultrathin forms for the electronics ensure minimal stresses on the tissue and highly conformal coverage, even for complex curvilinear surfaces, as confirmed by experimental and theoretical studies. In vivo, neural mapping experiments on feline animal

A remarkable feature of modern silicon electronics is its ability to remain functionally and physically invariant, almost indefinitely for many practical purposes. Here, we introduce a silicon-based technology that offers the opposite behavior: it gradually vanishes over time, in a well-controlled, programmed manner. Devices that are ‘transient’ in this sense create application possibilities that cannot be addressed with conventional electronics, such as active implants that exist for medically useful timeframes, but then completely dissolve and disappear via resorption by the body. We report a comprehensive set of materials, manufacturing schemes, device components and theoretical design tools for a complementary metal oxide semiconductor (CMOS) electronics of this type, together with four different classes of sensors and actuators in addressable arrays, two options for power supply and a wireless control strategy. A transient silicon device capable of delivering thermal therapy in an implantable mode and its demonstration in animal models illustrate a system-level example of this technology.

Gripping and holding of objects are key tasks for robotic manipulators. The development of universal grippers able to pick up unfamiliar objects of widely varying shape and surface properties remains, however, challenging. Most current designs are based on the multifingered hand, but this approach introduces hardware and software complexities. These include large numbers of controllable joints, the need for force sensing if objects are to be handled securely without crushing them, and the computational overhead to decide how much stress each finger should apply and where. Here we demonstrate a completely different approach to a universal gripper. Individual fingers are replaced by a single mass of granular material that, when pressed onto a target object, flows around it and conforms to its shape. Upon application of a vacuum the granular material contracts and hardens quickly to pinch and hold the object without requiring sensory feedback. We find that volume changes of less than 0.5% suffice to grip objects reliably and hold them with forces exceeding many times their weight. We show that the operating principle is the ability of granular materials to transition between an unjammed, deformable state and a jammed state with solid-like rigidity. We delineate three separate mechanisms, friction, suction, and interlocking, that contribute to the gripping force. Using a simple model we relate each of them to the mechanical strength of the jammed state. This advance opens up new possibilities for the design of simple, yet highly adaptive systems that excel at fast gripping of complex objects.stress-strain | packing density | friction | suction | interlocking

Many existing and envisioned classes of implantable biomedical devices require high performance electronics/sensors. An approach that avoids some of the longer term challenges in biocompatibility involves a construction in which some parts or all of the system resorbs in the body over time. This paper describes strategies for integrating single crystalline silicon electronics, where the silicon is in the form of nanomembranes, onto water soluble and biocompatible silk substrates. Electrical, bending, water dissolution, and animal toxicity studies suggest that this approach might provide many opportunities for future biomedical devices and clinical applications.

aqueous phase on the organic liquid, however, has not been commented upon nor rigorously assessed. To a first approximation, one assumes that the "interfacial" organic liquid behavior parallels that of the bulk phase. How do these observations compare to the phospholipid bilayer-water interface?Consider first the acyl chain region. In the center of a bilayer, e.g., composed of DMPC, the viscosity has been determined to be about 1.5 P, a value about 200 times greater than that of water and equivalent (approximately) to that of a light oil.26 However, from the center of the bilayer to the surface, 13C NMR has been used to demonstrate a 100-200-fold gradient of disorder (expressed as microviscosity).22 The hydrocarbon chains near the headgroups are much more crystalline, therefore, than in the center of the bilayer. The liposomal interfacial transfer process initially involves, as a result, solute "extraction" from an organic environment that is much more structured than a simple liquid. This situation may be reasonably expected to result in a significant slowing of the phase transfer process.At the headgroup region of a liposome, a very complex structure exists. The phosphatidylcholine headgroup binds water tightly: calorimetric experiments, for example, indicate that 10 mol of water per mole of synthetic lecithin is unfreezable at 0 °C;23 using (25) Guy, R.