Untethered robots miniaturized to the length scale of millimeter and below attract growing attention for the prospect of transforming many aspects of health care and bioengineering. As the robot size goes down to the order of a single cell, previously inaccessible body sites would become available for high-resolution in situ and in vivo manipulations. This unprecedented direct access would enable an extensive range of minimally invasive medical operations. Here, we provide a comprehensive review of the current advances in biomedical untethered mobile milli/microrobots. We put a special emphasis on the potential impacts of biomedical microrobots in the near future. Finally, we discuss the existing challenges and emerging concepts associated with designing such a miniaturized robot for operation inside a biological environment for biomedical applications.

Biomedical Applications of Untethered Mobile Milli/Microrobots

This paper discusses the biomimetic design and assembly of a 3g self-contained crawling robot fabricated through the integrated use of various microrobot technologies. The hexapod structure is designed to move in an alternating tripod gait driven by two piezoelectric actuators connected by sliding plates to two sets of three legs. We present results of both the kinematic and static analyses of the driving mechanism that essentially consists of three slider cranks in series. This analysis confirmed the force differential needed to propel the device. We then review various other microrobot technologies that have been developed including actuator design and fabrication, power and control electronics design, programming via a finite state machine, and the development of bioinspired fiber arrays. These technologies were then successfully integrated into the device. The robot is now functioning and we have already fabricated three iterations of the proposed device. We hope with further design iterations to produce a fully operational model in the near future

/pdf/towards-a-3g-crawling-robot-through-the-integration-of-7k4iec8rkn.pdf

Towards a 3g crawling robot through the integration of microrobot technologies

In a world where resources are scarce and urban areas consume the vast majority of these resources, it is vital to make cities greener and more sustainable. Advanced systems to improve and automate processes within a city will play a leading role in smart cities. From smart design of buildings, which capture rain water for later use, to intelligent control systems, which can monitor infrastructures autonomously, the possible improvements enabled by sensing technologies are immense. Ubiquitous sensing poses numerous challenges, which are of a technological or social nature. This paper presents an overview of the state of the art with regards to sensing in smart cities. Topics include sensing applications in smart cities, sensing platforms and technical challenges associated with these technologies. In an effort to provide a holistic view of how sensing technologies play a role in smart cities, a range of applications and technical challenges associated with these applications are discussed. As some of these applications and technologies belong to different disciplines, the material presented in this paper attempts to bridge these to provide a broad overview, which can be of help to researchers and developers in understanding how advanced sensing can play a role in smart cities.

The Role of Advanced Sensing in Smart Cities

Metasurfaces are two-dimensional arrangements of subwavelength scatterers that control the propagation of optical waves. Here, we show that cascaded metasurfaces, each performing a predefined mathematical transformation, provide a new optical design framework that enables new functionalities not yet demonstrated with single metasurfaces. Specifically, we demonstrate that retroreflection can be achieved with two vertically stacked planar metasurfaces, the first performing a spatial Fourier transform and its inverse, and the second imparting a spatially varying momentum to the Fourier transform of the incident light. Using this concept, we fabricate and test a planar monolithic near-infrared retroreflector composed of two layers of silicon nanoposts, which reflects light along its incident direction with a normal incidence efficiency of 78% and a large half-power field of view of 60°. The metasurface retroreflector demonstrates the potential of cascaded metasurfaces for implementing novel high-performance components, and enables low-power and low-weight passive optical transmitters.

Planar metasurface retroreflector

Wireless sensor networks are networks of compact microsensors with wireless communication capability. These small devices are relatively cheap with the potential to be disseminated in large quantities. Emerging applications of data gathering range from the environmental to the military. As autonomous devices they can provide pervasive distributed and collaborative network of computer nodes. Architectural challenges are posed for designers such as computational power, energy consumption, energy sources, communication channels and sensing capabilities. Embedded Systems provide the computational platform for hardware and software components to interact with the environment and other nodes. This survey presents the current state-of-the-art for wireless sensor nodes, investigating and analyzing these challenges. We discuss the characteristics and requirements for a sensor node mainly processing, communications, power and sensing components. In this survey we present a comprehensive comparative study of sensor nodes platforms, energy management techniques, off-the-shelf microcontrollers, battery types and radio devices.

/pdf/survey-on-wireless-sensor-network-devices-4s130ozayw.pdf

Survey on wireless sensor network devices

A 16 mm/sup 3/ autonomous solar-powered sensor node with bidirectional optical communication for distributed sensor networks has been demonstrated. The device digitizes integrated sensor signals and transmits/receives data over a free-space optical link. The system consists of three die - a 0.25 /spl mu/m CMOS ASIC, a 2.6 mm/sup 2/ SOI solar cell array, and a micromachined four-quadrant corner-cube retroreflector (CCR), allowing it to be used in a one-to-many network configuration. The CMOS ASIC includes a photosensor integrated 3 MHz oscillator, 69 pJ/bit optical receiver and 31 pJ/sample ADC.

/pdf/an-autonomous-16-mm-sup-3-solar-powered-node-for-distributed-4xv603f9n0.pdf

An autonomous 16 mm/sup 3/ solar-powered node for distributed wireless sensor networks

We have developed a new process for fabricating integrated, solar-powered microelectromechanical systems (MEMS) on a silicon-on-insulator (SOI) wafer. The intended applications for this process are autonomous microsystems, such as microrobots and distributed sensor networks. Two versions of the process have been created. The first combines solar cells and MEMS devices with NMOS transistors utilizing metal gates. This version has yielded solar cell efficiencies greater that 11%, a 200 cell array with an output of 88.5 V and transistor breakdown voltages above 25 V. Using this process, a fully integrated device has been demonstrated consisting of an electrostatic, gap-closing actuator being powered by an on-board buffer consisting of an NMOS inverter. The only external connections were ground and a 5 V control signal. A second version has also been developed which provides better solar cell performance and CMOS circuits utilizing polysilicon gates. This version has yielded solar cell efficiencies greater than 14%, a 90 cell array with an output over 50 V, and NMOS and PMOS devices with breakdown voltages greater than 50 V.

An SOI process for fabrication of solar cells, transistors and electrostatic actuators

We have demonstrated an autonomous two-legged microrobot which has taken its first steps The body of the robot is fabricated in a planarized silicon-on-insulator (SOI), two-layer polysilicon process and is 85 mm /spl times/ 4 mm /spl times/ 05 mm in size We previously reported initial leg motion from an off-board controller but have now incorporated control and power supplies onto the robot, resulting in autonomous operation for the first time This solar-powered microrobot has two, one degree-of-freedom (DOF) legs and drags its tail end Leg motion is generated via electrostatic inchworm motors on the robot body The robot is a three chip hybrid assembled from one chip which contains the robot's motors and legs, a second chip which integrates both solar cells and high voltage buffers, and a third chip which incorporates CMOS circuitry for sequencing the legs The robot has demonstrated 3 mm of motion shuffling sideways and has lifted its front end more than 300 /spl mu/m above the surface The total weight of the three-chip robot is only 102 mg

Solar powered 10 mg silicon robot

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An autonomous 16 mm/sup 3/ solar-powered node for distributed wireless sensor networks

An SOI process for fabrication of solar cells, transistors and electrostatic actuators

Solar powered 10 mg silicon robot