The development of an electronic skin is critical to the realization of artificial intelligence that comes into direct contact with humans, and to biomedical applications such as prosthetic skin. To mimic the tactile sensing properties of natural skin, large arrays of pixel pressure sensors on a flexible and stretchable substrate are required. We demonstrate flexible, capacitive pressure sensors with unprecedented sensitivity and very short response times that can be inexpensively fabricated over large areas by microstructuring of thin films of the biocompatible elastomer polydimethylsiloxane. The pressure sensitivity of the microstructured films far surpassed that exhibited by unstructured elastomeric films of similar thickness, and is tunable by using different microstructures. The microstructured films were integrated into organic field-effect transistors as the dielectric layer, forming a new type of active sensor device with similarly excellent sensitivity and response times.

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Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers

Human skin is a remarkable organ. It consists of an integrated, stretchable network of sensors that relay information about tactile and thermal stimuli to the brain, allowing us to maneuver within our environment safely and effectively. Interest in large-area networks of electronic devices inspired by human skin is motivated by the promise of creating autonomous intelligent robots and biomimetic prosthetics, among other applications. The development of electronic networks comprised of flexible, stretchable, and robust devices that are compatible with large-area implementation and integrated with multiple functionalities is a testament to the progress in developing an electronic skin (e-skin) akin to human skin. E-skins are already capable of providing augmented performance over their organic counterpart, both in superior spatial resolution and thermal sensitivity. They could be further improved through the incorporation of additional functionalities (e.g., chemical and biological sensing) and desired properties (e.g., biodegradability and self-powering). Continued rapid progress in this area is promising for the development of a fully integrated e-skin in the near future.

25th Anniversary Article: The Evolution of Electronic Skin (E-Skin): A Brief History, Design Considerations, and Recent Progress

MEDICAL LITERATURE has been deluged during the past few years with books and papers on penicillin; but a book which has been produced under the general editorship of Sir Alexander Fleming himself represents a complete and authoritative summary of penicillin therapy as it stands today.' The book contains a series of independent contributions by \"experienced and eminent men who have worked with penicillin in Great Britain\". Their opinions and practical methods differ slightly, and there is some overlapping; but these are not disadvantageous, comparison and contrast lending interest to the reading. In the first or general section of the book Fleming contributes two chapters, one on the history and development of penicillin, introducing some interesting sidelights in the romance of discovery, the other on the bacteriological control of penicillin therapy. In both chapters the information is set out in meticulous detail and with a clarity and simplicity which can be enjoyed by all readers. Fleming also gives the right perspective to the place of penicillin amongst the antibiotics and lays down the principles of treatment. Both chapters are well illustrated and are the most outstanding in the book. Included in this first section also are chapters on the chemistry and manufacture of penicillin and its pharmacy, pharmacology and methods of administration. The second section of the book is entirely clinical, giving each author's view on the use of penicillin therapy in a disease or an infection of some particular region of the body. The entire range of peniCillin-sensitive conditions is considered in twenty authoritative and clearly written chapters; these contain many references and illustrations. Dental and veterinary diseases are also given fairly full consideration. The final section is a condensed resume of much of the preceding chapters and is written for. the general practttioner. This chapter is superttuous: it does not contain enough detall to be of much practical value. The book as a Whole, however, will undoubtedly be considered a classical contribution to medical literature and is strongly recommended, not only because of the general interest of its topic, but as a reference book on penicillin therapy of hitherto unequalled excellence. The typography, although conforming to war economy standards, is clear and the paper is good. There is an excellent list of references and the index is satisfactory.

Gray's Anatomy

Flexible skin-attachable strain-gauge sensors are an essential component in the development of artificial systems that can mimic the complex characteristics of the human skin. In general, such sensors contain a number of circuits or complex layered matrix arrays. Here, we present a simple architecture for a flexible and highly sensitive strain sensor that enables the detection of pressure, shear and torsion. The device is based on two interlocked arrays of high-aspect-ratio Pt-coated polymeric nanofibres that are supported on thin polydimethylsiloxane layers. When different sensing stimuli are applied, the degree of interconnection and the electrical resistance of the sensor changes in a reversible, directional manner with specific, discernible strain-gauge factors. The sensor response is highly repeatable and reproducible up to 10,000 cycles with excellent on/off switching behaviour. We show that the sensor can be used to monitor signals ranging from human heartbeats to the impact of a bouncing water droplet on a superhydrophobic surface.

A flexible and highly sensitive strain-gauge sensor using reversible interlocking of nanofibres

Nerve regeneration is a complex biological phenomenon. In the peripheral nervous system, nerves can regenerate on their own if injuries are small. Larger injuries must be surgically treated, typically with nerve grafts harvested from elsewhere in the body. Spinal cord injury is more complicated, as there are factors in the body that inhibit repair. Unfortunately, a solution to completely repair spinal cord injury has not been found. Thus, bioengineering strategies for the peripheral nervous system are focused on alternatives to the nerve graft, whereas efforts for spinal cord injury are focused on creating a permissive environment for regeneration. Fortunately, recent advances in neuroscience, cell culture, genetic techniques, and biomaterials provide optimism for new treatments for nerve injuries. This article reviews the nervous system physiology, the factors that are critical for nerve repair, and the current approaches that are being explored to aid peripheral nerve regeneration and spinal cord repair.

Neural tissue engineering: strategies for repair and regeneration.

As the Weber test evaluates the slowly adapting fiber-receptor system (constant touch), the "moving two-point discrimination test" evaluates the innervation density of the quickly adapting fiber-receptor system which mediates the perception of touch stimuli moving across the hand. Results with this test in 39 hands used as controls and in 63 patients with nerve injuries show it to be a simple, quick, and valid diagnostic tool in nerve compression syndromes and nerve lacerations and an accurate prognosticator and monitor during sensory reeducation following nerve repair.

The moving two-point discrimination test: Clinical evaluation of the quickly adapting fiber/receptor system

Both moving and static two-point discrimination are valid measurements of functional sensibility in the hand. The present study investigated the interobserver variability of these measurements when two observers used the same testing instrument and the same definition of the testing procedure's end point. In testing 30 nerve-injured patients, interobserver variability was found to vary within 1 mm, or less, for moving two-point discrimination in 93.3% of the measurements and for static two-point discrimination in 86.8% of the measurements. In only two of the 30 measurements of moving two-point discrimination and in four of the measurements for static two-point discrimination were interobserver differences equal to 2 mm. Measurements for both moving and static two-point discrimination were analyzed statistically by linear regression and correlation co-efficient techniques. The measurements for two-point discrimination obtained with the protocol employed in this study were found to have an interobserver reliability at the p less than 0.00001 level.

Reliability of two-point discrimination measurements

The differential diagnosis of groin pain must consider problems of the ilioinguinal and/or genitofemoral nerve. These nerves may become injured during hernia surgery or lower quadrant surgical procedures. To treat injury to these nerves, it is critical to understand their anatomic variability. In the present study the pattern of cutaneous nerve branches in the inguinal region was investigated through dissection in 64 halves of 32 human embalmed anatomic specimens. In contrast to usual textual descriptions, four different types of cutaneous branching patterns are identified: type A, with a dominance of genitofemoral nerve in the scrotal/labial and the ventromedial thigh region. In type A, the ilioinguinal nerve gives no sensory contribution to these regions (43.7 percent). In type B, with a dominance of ilioinguinal nerve, the genitofemoral nerve shares a branch with the ilioinguinal and gives motor fibers to cremaster muscle in the inguinal canal, but has no sensory branch to the groin (28.1 percent). In type C, with a dominance of genitofemoral nerve, the ilioinguinal nerve has sensory branches to the mons pubis and inguinal crease together with an anteroproximal part of the root of the penis or labia majora. The nerve was found to share a branch with the iliohypogastric nerve (20.3 percent). In type D, cutaneous branches emerge from both the ilioinguinal and the genitofemoral nerves. Additionally, the ilioinguinal nerve innervates the mons pubis and inguinal crease together with a very anteroproximal part of the root of the penis or labia majora (7.8 percent). The described patterns of innervation were bilaterally symmetric in 40.6 percent of the cadavers. The anatomic variability of both nerves has implications for all surgeons operating in the groin region and for those caring for the patient with groin pain.

Anatomic variability of the ilioinguinal and genitofemoral nerve: Implications for the treatment of groin pain

Two-point discrimination tester

The ability to predict hand function based upon the degree of sensory impairment is required in determining disability rating, evaluating patients for reconstructive surgery, measuring end results of nerve repairs, and following peripheral neuropathies. The present study evaluated the ability of four tests of sensibility to predict hand function. It was found that the moving two-point discrimination test best correlated with the patient's ability to identify objects with the fingertips, p p

A. Lee Dellon

Papers

The moving two-point discrimination test: Clinical evaluation of the quickly adapting fiber/receptor system

Reliability of two-point discrimination measurements

Anatomic variability of the ilioinguinal and genitofemoral nerve: Implications for the treatment of groin pain

Two-point discrimination tester

Evaluation of functional sensation in the hand.