As the world pushes into ever-higher frequency regimes for wireless communications, transistor-based technologies--long the backbone of RF systems--face fundamental scaling limits. In particular, transistor gain falls steeply with frequency for fixed input power, mixer efficiency falls with frequency for similar reasons, resonator losses climb and degrade filter performance, and multi-chip module packaging shifts from simple interposer connections to highly specialized engineered RF systems. The result is that conventional electronic solutions grow noisier, less efficient, and more expensive to implement at scale. By contrast, acoustoelectric devices, which operate using completely distinct physical phenomena that exploit the strong coupling between charges and piezoelectric acoustic waves, have the potential to enable RF signal processing with low loss, inherent nonreciprocity, and high power efficiency at microwave frequencies. In this talk I will discuss my group's progress toward a new class of classical microwave frequency phononic devices created by heterogeneously integrating semiconductors and piezoelectric materials. The combination of these materials and the various acoustoelectric interactions they enable allows for all passive, active, and nonreciprocal functionalities to be achieved on a single chip, such as amplifiers, gain-boosted filters, oscillators, isolators, circulators, mixers, and switches. Combined with their well-established ability to perform passive functions such as narrow-band filtering and duplexing, these acoustoelectric phononic integrated circuits pave the way for a new era of radio frequency signal processing on a chip. I will then discuss opportunities and challenges associated with scaling these devices from the S-band devices we have developed into higher frequency microwave bands and millimeter wave bands.

Recent advances in microfabrication and biotechnology have enabled the development of a wide variety of miniaturized implantable systems. Their applications range from monitoring and diagnosis to localized treatments. All these systems include, among other things, electronic components and require an energy source to power them. Although a battery can always be used, replacing it (and, more generally, the whole system) is not a routine or straightforward procedure, particularly in the case of a leadless pacemaker, that is implanted directly into the patient's heart chamber. In this case, energy harvesting is a promising alternative to traditional batteries, making the systems autonomous for longer than using batteries, and enabling further miniaturization and enhanced functionality.

Biomechanical energy is particularly intense in the heart region, and has the specificity of being permanently present, unlike in other parts of the human body. Thus, converting a small fraction of available mechanical energy into electricity to power a leadless pacemaker seems an ideal solution. However, the constraints and requirements in terms of dimensions, power density, reliability and durability specific to this application present unprecedented challenges.

In this talk, we will present a summary of the state-of-the-art means currently being studied to meet these challenges. We'll then focus on the MEMS devices we've studied for this purpose: piezoelectric micro-cantilevers, piezoelectric microspirals, 3D electrostatic microtransducers, Silicon-on-Glass electrostatic MEMS, and some specific interface circuits. We will present the accelerated ageing method we have developed to assess the durability of piezoelectric microcantilevers, enabling to reproduce in just a few months what a piezoelectric device is mechanically subjected to an operating life of 20 years, corresponding to around 600 million heartbeats. Finally, we will discuss the prospects for increasing the power density of MEMS energy harvesters, bringing them closer to their physical limits.

An energy harvesting from ambient radio waves is very important technology for mW applications to reduce a battery, e.g. IoT sensors, vital sensors, etc. Compared with the other energy harvesters, like PowerMEMS, power generation by heat, etc., the energy harvesting from the ambient radio waves is very stable to generate the power everywhere and every time because the distributed power source of the radio waves is originally artificial for wireless broadcasting and communications. However, it contains the same weak point with all harvesters that available power is not enough to satisfy the user requirement of the energy. Only in the energy harvesting from the ambient radio waves, we can increase the received power when we put a special transmitter for wireless power only, which can increase the transmitting power. It is named a "Radiative Wireless Power Transfer (WPT)". We can apply the same harvester (rectifying antenna = rectenna) technology both for the energy harvesting and the WPT.

In recent 10 years, the WPT technology and business is expanded in the world. It is based on the discussion of new radio regulation in consideration of suppression of unexpected interference to existing radio waves like WiFi and of keeping safety of human. In 2022, ITU-R (International Telecommunication Union - Radiocommunication Sector) recommends frequencies suitable for the WPT. In the same 2022, Japanese government establish a new radio regulation for the WPT at 920MHz band, 2.4GHz band, and 5.7GHz band. In US, the WPT system is considered as one of ISM (Industrial, Scientific, and Medical) applications and a lot of start-up companies of the WPT born and produce the commercial WPT equipment. Current WPT applications are similar with the application of energy harvesters, battery-less sensors. In the current step of the WPT business, good rectenna technology is required. When the input radio wave power to the rectenna is enough to excite a diode/CMOS on the rectifying circuit, over several tens of milliwatts, the RF-DC conversion efficiency of the rectenna has already reached at > 90% at 920MHz band and at 2.4GHz and at 85% at > 75% at 24/28GHz band in Japan. When input radio wave power is not enough like the energy harvesting system, the RF-DC conversion efficiency is still low and we need a special technique to increase the efficiency. This is the important technology in the first step of the WPT.

In the second step, we need a beam forming technology in the transmitter to increase the receiving power by focusing and/or chasing beam on the moving receiver. A phased array antenna is usually applied for beam forming. We can charge a mobile phone and can fly a drone by focusing radio wave with high beam efficiency when we have a good phased array antenna technology. In Kyoto University, we have developed a low cost and high efficiency phased array antenna at 28GHz in 2025. We also fly the battery-less micro drone only by the beamed microwave at 5.8GHz at distance of approximately 70 cm. In future, we expect to build a Solar Power Satellite (SPS) with 1GW solar cells and 2km phased array antenna in geo-stationary orbit in 26,000km above in 2050. There are some big R&D projects for the SPS not only in Japan but also in US and China. We use the same and advanced technology both for the SPS, WPT, and energy harvesting from ambient radio waves.

In this talk, I will introduce the recent advance of the energy harvesting technology from ambient radio waves and of the WPT. I also introduce the current commercial and future WPT applications and discussion status of the radio regulation of the WPT in the world.

During former President Barack Obama’s 2013 State of the Union Address, he remarked on the potential for additive manufacturing—or colloquially, “three-dimensional (3D) printing”—“to revolutionize the way we make almost everything.” Despite this potential, progress has been impeded by broad challenges associated with 3D printing technologies at smaller length scales. Recent breakthroughs in 3D micro/nanoprinting, however, hold unique promise to overcome past barriers and enable new frontiers for fundamental and applied research. In this invited presentation, Prof. Ryan D. Sochol will discuss how his Bioinspired Advanced Manufacturing (BAM) Laboratory is leveraging “Two-Photon Direct Laser Writing”—an additive manufacturing technique with printing resolutions down to the 100 nanometer range—for emerging applications, including: (i) soft microrobotic surgical instruments for minimally invasive interventions, (ii) 3D organ-on-a-chip systems that mimic bioarchitectural conditions, and (iii) 3D microneedle technologies for microinjection and therapeutic delivery.