Millimeter-wave backscatter can simultaneously support high-precision sensing and massive communication and represent one prominent technical evolution in next-generation wireless systems. The backscatter tags should ideally work across a wide mmWave spectrum range with consistent signal strength and angular coverage to accommodate highly diverse application scenarios. However, existing tags made of resonant antennas and RFICs only achieve a few GHz of bandwidth and hardly meet these requirements. In this paper, we present UniScatter, a new backscatter tag structure based on metamaterials. The key design of UniScatter is a graphene-based modulator and a lens-based retroreflector, which have consistent electromagnetic responses across an extensive frequency range and wide angular field-of-view. We have developed a robust fabrication process for UniScatter, and tested it on various mmWave sensing and communication devices. Our field tests show that UniScatter can backscatter signals across a wide frequency band from 24 GHz to 77 GHz with consistently high signal strength and wide angular coverage in 3D space.

Next generation wireless networks embrace mmWave technology for its high capacity. Yet, mmWave radios bear a fundamental coverage limitation due to the high directionality and propagation artifacts. In this paper, we explore an economical paradigm based on 3D printing technology for mmWave coverage expansion. We propose MilliMirror, a fully passive metasurface, which can reshape and resteer mmWave beams to anomalous directions to illuminate the coverage blind spots. We develop a closed-form model to efficiently synthesize the MilliMirror design with thousands of unit elements and across a wide frequency band. We further develop an economical process based on 3D printing and metal deposition to fabricate MilliMirror. Our field test results show that MilliMirror can effectively fill the coverage holes and operate transparently to the standard mmWave beam management protocols.

Organic thin film transistor (OTFT) circuits for sensor tags were implemented by all-additive solution processes. The effect of device variations on the yield was evaluated, to account for the constraints of existing OTFT processes. The opportunities and challenges of additive printing fabrication are presented in the context of integrated sensor tags that monitor temperature dose in smart packaging.

Printing as a manufacturing technique is a promising approach to fabricate low-cost, flexible, and large area electronics. Over the last two decades, a wide range of applications has been explored, among them displays, sensors, and printed radio-frequency identification devices. Some of these turned out to be challenging to commercialize due to the required infrastructure investment, accuracy or performance expectations compared to incumbent technologies. However, the progress in terms of material science, device, and process technology now makes it possible to target some realistic applications such as printed sensor labels. The journey leading to this exciting opportunity has been complex. This review describes the experience and current efforts in developing the technology at PARC, a Xerox Company. Printed smart labels open up low-cost solutions for tracking and sensing applications that require high volumes and/or would benefit from disposability. Examples include radiation tags, one-time use medical sensors, tracking the temperature of pharmaceuticals at the item level, and monitoring food sources for spoilage and contamination. Higher performance can be achieved with printed hybrid electronics, integrating microchip-based signal processing, wireless communication, sensing, multiplexing, as well as ancillary passive elements for low-profile microelectronic devices, opening up further applications. This technology offers custom circuitry for demanding applications and is complementary to mass printed transistor circuits. As an example, we describe a prototype sense-and-transmit system, focusing particularly on issues of integration, such as impedance matching between the sensor and circuits, robust printed interconnection of the chips, and compatible interface electronics between printed and discrete parts. Next-generation technologies will enable printing of entire smart systems using microchip inks. A new printing concept for the directed assembly of silicon microchips into functional circuits is described. The process is scalable and has the potential to enable additive, digital manufacturing of high-performance electronic systems.