Search

We present in situ calorimetry, thermal conductivity, and thermal diffusivity measurements of materials using temperature-sensing optical wireless integrated circuits (OWiCs). These microscopic and untethered optical sensors eliminate input wires and reduce parasitic effects. Each OWiC has a mass of ∼100 ng, a 100-μm-scale footprint, and a thermal response time of microseconds. We demonstrate that they can measure the thermal properties of nearly any material, from aerogels to metals, on samples as small as 100 ng and over thermal diffusivities covering four orders of magnitude. They also function over a broad temperature range, and we present proof-of-concept measurements of the thermodynamic phase transitions in both liquid crystal 5CB and gadolinium.

Cilial pumping is a powerful strategy used by biological organisms to control and manipulate fluids at the microscale. However, despite numerous recent advances in optically, magnetically and electrically driven actuation, development of an engineered cilial platform with the potential for applications has remained difficult to realize

While CMOS scaling has long been driven by economic and performance concerns in macroscale systems such as computers and smartphones, it has also been recognized that such physically small electronic components could pave the way to vanishingly small autonomous systems. Originally dubbed “smart dust”, these emerging systems include ultra-small wireless sensors, ID tags, and even robots. Such “Smart Dust” was envisioned to be smaller than a grain of sand, yet measuring and reporting signals around it while being powered and communicating entirely wirelessly [1], [2].

In vivo, chronic neural recording is critical to understand the nervous system, while a tetherless, miniaturized recording unit can render such recording minimally invasive. We present a tetherless, injectable micro-scale opto-electronically transduced electrode (MOTE) that is $\sim 60~\mu \text{m}\,\,\times 30~\mu \text{m}\,\,\times 330~\mu \text{m}$ , the smallest neural recording unit to date. The MOTE consists of an AlGaAs micro-scale light emitting diode ( $\mu $ LED) heterogeneously integrated on top of conventional 180nm complementary metal-oxide-semiconductor (CMOS) circuit. The MOTE combines the merits of optics (AlGaAs $\mu $ LED for power and data uplink), and of electronics (CMOS for signal amplification and encoding). The optical powering and communication enable the extreme scaling while the electrical circuits provide a high temporal resolution ( $ ). This paper elaborates on the heterogeneous integration in MOTEs, a topic that has been touted without much demonstration on feasibility or scalability. Based on photolithography, we demonstrate how to build heterogenous systems that are scalable as well as biologically stable– the MOTEs can function in saline water for more than six months, and in a mouse brain for two months (and counting). We also present handling/insertion techniques for users (i.e. biologists) to deploy MOTEs with little or no extra training. [2020-0080]

We have developed a fabrication process that can be used to build millions of microscopic, electronically-integrated robots. Our procedure includes steps for building silicon microelectronics, building components for actuation, encapsulation steps, and a process for releasing the robots into aqueous environments. Each step is carried out massively in parallel, allowing us to build over a million robots on a single 4-inch wafer. Broadly, the new actuators and fabrication protocols presented here offer a generic platform and can be used to make a wide range of silicon-based, functional robotic systems that are too small to be resolved by the naked eye.

Significance The smallest objects resolvable by the unaided human eye are approximately 100 μm in size. This limit sets a boundary between the familiar and the microscopic, the visible and invisible worlds. Here we describe the fabrication of tiny wireless sensors, optical wireless integrated circuits (OWICs) for optical wireless integrated circuits. OWICs are truly microscopic in size, visible to the naked eye at best as a tiny, undifferentiated speck, yet they can sense their environment and report the information back to the macroscopic world. They have potential applications in many areas of science and technology, ranging from neuroscience to chemical sensing.

Recording neural activity in live animals in vivo with minimal tissue damage is one of the major barriers to understanding the nervous system. This paper presents the technology for a tetherless opto-electronic neural interface based on 180 nm CMOS circuits, heterogeneously integrated with an AlGaAs diode that functions as both a photovoltaic and light emitting diode. These microscale opto-electrically transduced electrodes (MOTEs) are powered by and communicate through an optical interface, simultaneously enabling high temporal-resolution electrical measurements without a tether or a bulky RF coil. The MOTE presented here is 250 μ m × 57 μ m, consumes 1 μ W of electrical power, and is capable of capturing and encoding neural signals before transmitting the encoded signals. The measured noise floor is as low as 15 μ VRMS at a 15 kHz bandwidth.

Fifty years of Moore’s law scaling in microelectronics have brought remarkable opportunities for the rapidly evolving field of microscopic robotics1–5. Electronic, magnetic and optical systems now offer an unprecedented combination of complexity, small size and low cost6,7, and could be readily appropriated for robots that are smaller than the resolution limit of human vision (less than a hundred micrometres)8–11. However, a major roadblock exists: there is no micrometre-scale actuator system that seamlessly integrates with semiconductor processing and responds to standard electronic control signals. Here we overcome this barrier by developing a new class of voltage-controllable electrochemical actuators that operate at low voltages (200 microvolts), low power (10 nanowatts) and are completely compatible with silicon processing. To demonstrate their potential, we develop lithographic fabrication-and-release protocols to prototype sub-hundred-micrometre walking robots. Every step in this process is performed in parallel, allowing us to produce over one million robots per four-inch wafer. These results are an important advance towards mass-manufactured, silicon-based, functional robots that are too small to be resolved by the naked eye. A new class of voltage-controllable electrochemical actuators that are compatible with silicon processing are used to produce over one million sub-hundred-micrometre walking robots on a single four-inch wafer.

Measuring the behavior of redox-active molecules in space and time is crucial for better understanding of chemical and biological systems and for the development of new technologies. Optical schemes are non-invasive, scalable and can be applied to many different systems, but usually have a slow response compared to electrical detection methods. Furthermore, many fluorescent molecules for redox detection degrade in brightness over long exposure times. Here we show that the photoluminescence of pixel arrays of an atomically thin two-dimensional (2D) material, a monolayer of MoS$_{2}$, can image spatial and temporal changes in redox molecule concentration in real time. Because of the strong dependence of MoS$_{2}$ photoluminescence on doping and sensitivity to surface changes characteristic of 2D materials, changes in the local chemical potential significantly modulate the photoluminescence of MoS$_{2}$, with a sensitivity of 0.9 mV/$\sqrt{Hz}$ on a 5 $\mu$m by 5 $\mu$m pixel, corresponding to better than parts-per-hundred changes in redox molecule concentration down to nanomolar concentrations at 100 ms frame rates. The real-time imaging of electrochemical potentials with a fast response time provides a new strategy for visualizing chemical reactions and biomolecules with a 2D material screen.

Recording neural activity in live animals in vivo poses several challenges. Electrical techniques typically require electrodes to be tethered to the outside world directly via a wire, or indirectly via an RF Coil [1], which is much larger than the electrodes themselves. Tethered implants result in residual motion between neurons and electrodes as the brain moves, and limits our ability to measure from peripheral nerves in moving animals, especially in smaller organisms such as zebra fish or fruit flies. On the other hand, optical techniques, which are becoming increasingly powerful, are nonetheless often limited to subsets of neurons in any given organism, impeded by scattering of the excitation light and emitted fluorescence, and limited to low temporal resolution [2]. Here we present the electronics for an untethered electrode unit, powered by, and communicating through a microscale optical interface, combining many benefits of optical techniques with high temporal-resolution recording of electrical signals.