Emerging applications in brain-machine interface systems require high-resolution, chronic multisite cortical recordings, which cannot be obtained with existing technologies due to high power consumption, high invasiveness, or inability to transmit data wirelessly. In this paper, we describe a microsystem based on electrocorticography (ECoG) that overcomes these difficulties, enabling chronic recording and wireless transmission of neural signals from the surface of the cerebral cortex. The device is comprised of a highly flexible, high-density, polymer-based 64-channel electrode array and a flexible antenna, bonded to 2.4 mm × 2.4 mm CMOS integrated circuit (IC) that performs 64-channel acquisition, wireless power and data transmission. The IC digitizes the signal from each electrode at 1 kS/s with 1.2 μV input referred noise, and transmits the serialized data using a 1 Mb/s backscattering modulator. A dual-mode power-receiving rectifier reduces data-dependent supply ripple, enabling the integration of small decoupling capacitors on chip and eliminating the need for external components. Design techniques in the wireless and baseband circuits result in over 16× reduction in die area with a simultaneous 3× improvement in power efficiency over the state of the art. The IC consumes 225 μW and can be powered by an external reader transmitting 12 mW at 300 MHz, which is over 3× lower than IEEE and FCC regulations.

This paper presents a novel inkjet-printed humidity sensor tag for passive radio-frequency identification (RFID) systems operating at ultrahigh frequencies (UHFs). During recent years, various humidity sensors have been developed by researchers around the world for HF and UHF RFID systems. However, to our best knowledge, the humidity sensor presented in this paper is one of the first passive UHF RFID humidity sensor tags fabricated using inkjet technology. This paper describes the structure and operation principle of the sensor tag as well as discusses the method of performing humidity measurements in practice. Furthermore, measurement results are presented, which include air humidity-sensitivity characterization and tag identification performance measurements.

This article focuses on the fabrication and characterization of stretchable interconnects for wearable electronics applications. Interconnects were screen-printed with a stretchable silver-polymer composite ink on 50-μm thick thermoplastic polyurethane. The initial sheet resistances of the manufactured interconnects were an average of 36.2 mΩ/◽, and half the manufactured samples withstood single strains of up to 74%. The strain proportionality of resistance is discussed, and a regression model is introduced. Cycling strain increased resistance. However, the resistances here were almost fully reversible, and this recovery was time-dependent. Normalized resistances to 10%, 15%, and 20% cyclic strains stabilized at 1.3, 1.4, and 1.7. We also tested the validity of our model for radio-frequency applications through characterization of a stretchable radio-frequency identification tag.

Wireless body-centric sensing systems have an important role in the fields of biomedicine, personal healthcare, safety, and security. Body-centric radio-frequency identification (RFID) technology provides a wireless and maintenance-free communication link between the human body and the surroundings through wearable and implanted antennas. This enables real-time monitoring of human vital signs everywhere. Seamlessly integrated wearable and implanted miniaturized antennas thus have the potential to revolutionize the everyday life of people, and to contribute to independent living. Low-cost and low-power system solutions will make widespread use of such technology become reality. The primary target applications for this research are body-centric sensing systems and the relatively new interdisciplinary field of wireless brain-machine interface (BMI) systems. Providing a direct wireless pathway between the brain and an external device, a wireless brain-machine interface holds an enormous potential for helping people suffering from severely disabling neurological conditions to communicate and manage their everyday life more independently. In this paper, we discuss RFID-inspired wireless brain-machine interface systems. We demonstrate that mm-size loop implanted antennas are capable of efficiently coupling to an external transmitting loop antenna through an inductive link. In addition, we focus on wearable antennas based on electrically conductive textiles and threads, and present design guidelines for their use as wearable-antenna conductive elements. Overall, our results constitute an important milestone in the development of wireless brain-machine interface systems, and a new era of wireless body-centric systems.

A small and flexible metal mountable UHF RFID tag antenna, utilizing a high-permittivity substrate material is presented. The tag is composed of a small single-layer T-matched dipole antenna, on a flexible ceramic (BaTiO₃) polymer (polydimethylsiloxane) composite substrate, with a thickness of 1.5 mm. The flexibility of the substrate allows it to be mounted on flat and cylindrical metallic surfaces. The performance of the developed tag is evaluated through simulations and measurements on both flat and cylindrical metallic platforms of various sizes. The results show that the tag achieves state-of-the-art size-performance ratio while meeting the key requirements of an affordable RFID tag with a simple and flexible structure.

We present the fabrication and testing of graphene-based dipole antennas on cardboard, which is a promising low-cost, recyclable, and flexible substrate for future wireless electronics. The letter presents the details of the manufacturing, as well as results from the measurements and simulations. The measured sheet resistance of graphene antenna is 1.9 Ω/sq. Overall, a graphene-based planar dipole antenna with the length of 143 mm achieved the measured total efficiency of 40% and the realized gain of - 2.18 dBi at 889 MHz. Moreover, a passive ultra-high-frequency radio-frequency tag based on a graphene dipole antenna on cardboard achieved the attainable read range of more than 5 m at 950 MHz.