The detection techniques used in biosensors can be broadly classified into label-based and label-free. Label-based detection relies on the specific properties of labels for detecting a particular target. In contrast, label-free detection is suitable for the target molecules that are not labeled or the screening of analytes which are not easy to tag. Also, more types of label-free biosensors have emerged with developments in biotechnology. The latest developed techniques in label-free biosensors, such as field-effect transistors-based biosensors including carbon nanotube field-effect transistor biosensors, graphene field-effect transistor biosensors and silicon nanowire field-effect transistor biosensors, magnetoelastic biosensors, optical-based biosensors, surface stress-based biosensors and other type of biosensors based on the nanotechnology are discussed. The sensing principles, configurations, sensing performance, applications, advantages and restriction of different label-free based biosensors are considered and discussed in this review. Most concepts included in this survey could certainly be applied to the development of this kind of biosensor in the future.

No abstract

We propose a flexible wireless pressure sensor, which uses a graphene/polydimethylsiloxane (GR/PDMS) sponge as the dielectric layer. The sponge is sandwiched between two surfaces of a folded flexible printed circuit with patterned Cu as the antenna and electrode. By adjusting graphene and NH 4 HCO 3 concentrations, a composite with 20% concentration of NH 4 HCO 3 and 2% concentration of graphene as the dielectric layer is obtained, which exhibits high sensitivity (2.2 MHz/kPa), wide operating range (0–500 kPa), rapid response time (~7 ms), low detection limit (5 Pa), and good stability, recoverability, and repeatability. In addition, the sensor is sensitive to finger bending and facial muscle movements for smile and frown, that are transmitted using wireless electromagnetic coupling; therefore, it has potential for a wide range of applications such as intelligent robots, bionic-electronic skin and wearable electronic devices.

No abstract

There is always a temperature difference of more than 10 degrees between the human body, as a sustainable heat source, and the ambient temperature. Converting body heat into electricity that in turn is used to drive personal medical electronics is of significance in smart wearable medicine. To avoid the frangibility and complex preparation of traditional thermoelectric materials, we fabricated a gel electrolyte-based thermogalvanic generator with Fe 3+ /Fe 2+ as a redox pair, which presents not only moderate thermoelectric performance but also excellent flexibility. With a micropore-widespread polyvinylidene fluoride diaphragm implanted in the gel, a thermal barrier was created between the two halves, effectively improving the Seebeck coefficient by reducing its thermal conductivity. Considering the superior temperature response of the gel, a self-powered body temperature monitoring system was established by conformally affixing it to the forehead. Meanwhile, the gel patch with a high specific heat capacity can effectively cool down fever patients. This work may offer a new train of thought for exploiting self-powered wearable medical electronics by scavenging low-grade body heat.