Daniel S. Drew

Postdoc, Stanford, Mechanical Eng.
PhD, UC Berkeley, Electrical Eng.
email me: dsdrew at stanford.edu

In the near future, swarms of millimeter scale robots will be vital and common tools in industrial, commercial, and personal settings. The research effort to get us there is inherently interdisciplinary and represents a tremendous opportunity for collaboration, for training a new generation of interdisciplinary investigators, and for forging new ties between the worlds of industry, academia, and design; I look forward to pushing it forward.

I am looking for PhD students and a Postdoc to work with starting Fall 2021.
Apply for ECE or ME at the University of Utah and reach out to me directly!

Captain's Log
• I am thrilled to be joining the department of Electrical and Computer Engineering, and the interdisciplinary Robotics Center, at the University of Utah starting in Fall 2021.
• My paper got accepted for presentation at Hilton Head 2020. Looking forward to getting the chance to peek at the future of MEMS (and to playing beach volleyball) (2/14/20) (Unfortunately this workshop was cancelled, and there has been very little beach volleyball this spring. --Ed.)
• I've been invited to give a talk on microrobot swarms at the San Francisco Exploratorium on January 23rd during their After Dark programming! (12/12/19)
• Our paper got accepted to CHI2020! I'm excited to talk to more HRI researchers about future work grounded by the limitations of microrobot hardware. (12/9/19)
• A great article about the ionocraft appeared on IEEE Spectrum! (2/6/19)
• I have officially completed my PhD and will start as a postdoctoral scholar at Stanford in January! (12/15/18)
• My work with Kris Pister was featured in the Berkeley Engineer magazine Fall 2018 issue (11/15/18)
• I presented a poster at the Bay Area Robotics Symposium; lots of impressive talks from faculty, and lots of impressive research from their students- Inspiring! (11/9/18)
• I have been awarded the Intelligence Community Postdoctoral Research Fellowship for my proposal "Design and Control of Heterogeneous Microrobot Swarms." I'm very excited to be working with Sean Follmer at Stanford. Funding for research on microrobots - hurray! (8/8/18)

About Me
I'm a huge sci-fi (and everything else) reader. Here's a link to my goodreads page. I've done a fair amount of both solo and group world traveling and look forward to a lifetime of more. Here's a link to my extremely sporadically updated Flickr page. Send me an email with your wild dreams of the future; I want to hear it all.

I received my B.S. in Materials Science and Engineering from Virginia Tech in 2013. My past research includes electromagnetic railguns and polymer-metal nanoparticle compounds for energy efficient mechanical switching. I began the MS/PhD program at UC Berkeley in Fall 2013 with a MEMS concentration. I was also awarded an NSF Graduate Research Fellowship in 2013.

For my PhD, I worked with Professor Kris Pister on ionocraft, flying microrobots powered by atmospheric ion engines. I also did some work with Professor Bjoern Hartmann on developing novel systems for debugging in the field of HCI. I now work with Professor Sean Follmer at Stanford on human-robot interaction and exploring new strategies for turning centimeter-scale robots into useful tools.

Journal/Conference Papers
Lightweight High Voltage Generator for Untethered Electroadhesive Perching of Micro Air Vehicles
Sanghyeon Park, Daniel S Drew, Sean Follmer, Juan Rivas-Davila RA-L 2020
The limited in-flight battery lifetime of centimeterscale flying robots is a major barrier to their deployment, especially in applications which take advantage of their ability to reach high vantage points. In this paper, we motivate the need for application-specific power electronics solutions for electroadhesive perching, develop a useful figure of merit (the “specific voltage”) for comparing and guiding efforts, and walk through the design methodology of a system implementation. We conclude by showing that this high voltage power supply enables, for the first time in the literature, tetherless electroadhesive perching of a commercial micro quadrotor.
Link to the paper

User-defined Swarm Robot Control
Lawrence H Kim, Daniel S Drew, Veronika Domova, Sean Follmer, CHI 2020, Best Paper Award Honorable Mention
A swarm of robots can accomplish more than the sum of its parts, and swarm systems will soon see increased use in applications ranging from tangible interfaces to search and rescue teams. However, effective human control of robot swarms has been shown to be demonstrably more difficult than controlling a single robot, and swarm-specific interactions methodologies are relatively underexplored. As we envision even non-expert users will have more daily in-person encounters with different numbers of robots in the future, we present a user-defined set of control interactions for tabletop swarm robots derived from an elicitation study.
Link to the paper

Low Level Control of a Quadrotor with Deep Model-Based Reinforcement Learning
Nathan O Lambert, Daniel S Drew, Joseph Yaconelli, Roberto Calandra, Sergey Levine, Kristofer S J Pister, Robotics and Automation Letters 2019
To address the problem of rapidly generating low-level controllers without domain knowledge or a priori knowledge of system dynamics, we propose using model-based reinforcement learning (MBRL) trained on few minutes of automatically generated data. In this paper, we explore the capabilities of MBRL on a Crazyflie quadrotor with rapid dynamics where existing classical control schemes offer a baseline against the new method's performance. To our knowledge, this is the first use of MBRL for low-level controlled hover of a quadrotor using only on-board sensors, direct motor input signals, and no initial dynamics knowledge.
Link to the paper

MIMSY: The Micro Inertial Measurement System for the Internet of Things
Craig Schindler, Daniel S Drew, Brian Kilberg, Felipe Campos, Soichiro Yanase, Kristofer S J Pister, IEEE World Forum on Internet of Things (WF-IOT) 2019
The Micro Inertial Measurement System (MIMSY) is an open-source wireless sensor node for Internet of Things applications, specifically designed for a small system volume while maintaining functionality and extensibility. MIMSY is a 16mm × 16mm node with an Arm Cortex-M3 microprocessor, 802.15.4 wireless transceiver, and a 9-axis IMU. The system is fully compatible with the OpenWSN wireless sensor networking stack, which enables the straightforward implementation of standards-compliant 6TiSCH mesh networks using MIMSY motes.
Link to the paper

Wifröst: Bridging the Information Gap for Debugging of Networked Embedded Systems
Will McGrath, Jeremy Warner, Mitchell Karchemsky, Andrew Head, Daniel Drew, Bjoern Hartmann, UIST 2018
This paper presents WiFröst, a new approach for debugging these systems using instrumentation that spans from the device itself, to its communication API, to the wireless router and back-end server. WiFröst automatically collects this data, displays it in a web-based visualization, and highlights likely issues with an extensible suite of checks based on analysis of recorded execution traces.
Link to the paper

MEMS-Actuated Carbon Fiber Microelectrode for Neural Recording
Rachel S Zoll, Craig B Schindler, Travis L Massey, Daniel S Drew, Michel M Maharbiz, Kristofer S J Pister, MNMC 2018
We present an electrostatic-based actuator capable of inserting individual carbon fiber microelectrodes which elicit minimal to no adverse biological response. The device is shown to insert a carbon fiber recording electrode into an agar brain phantom and can record an artificial neural signal in saline. This technique provides a platform generalizable to many microwire-style recording electrodes.
Link to the paper

Towards Controlled Flight of the Ionocraft: A Flying Microrobot Using Electrohydrodynamic Thrust With Onboard Sensing and No Moving Parts
Daniel S Drew, Nathan Lambert, Craig Schindler, Kristofer S J Pister, Robotics and Automation Letters 2018
This work presents an insect-scale microrobot that flies silently and with no mechanical moving parts, using a mechanism with no analogue in the natural world: electrohydrodynamic thrust produced by ions generated via corona discharge. For the first time, attitude and acceleration data is continuously collected from takeoff and sustained flight of a 2cm x 2cm, 30mg ``ionocraft'' carrying a 37mg 9-axis commercial IMU on FlexPCB payload, with external tethers for power and data transfer. The ionocraft's steady state thrust versus voltage profile, dynamic response to a time-varying signal around a high voltage DC bias point, and aerodynamic drag at incident angles around 90 degrees are measured. These experimental measurements, as well as measured IMU sensor noise, are inserted into a Matlab Simulink simulation environment. Simulation shows controlled hovering and planned flight in arbitrary straight trajectories in the X-Y plane.
Link to the paper

Bifröst: Visualizing and Checking Behavior of Embedded Systems across Hardware and Software
Will McGrath, Daniel Drew, Jeremy Warner, Majeed Kazemitabaar, Mitchell Karchemsky, David Mellis, Bjoern Hartmann, UIST 2017
This paper presents a new development environment designed to illuminate the boundary between embedded code and circuits. Bifröst automatically instruments and captures the progress of the user's code, variable values, and the electrical and bus activity occurring at the interface between the processor and the circuit it operates in. This data is displayed in a linked visualization that allows navigation through time and program execution, enabling comparisons between variables in code and signals in circuits. Automatic checks can detect low-level hardware configuration and protocol issues, while user-authored checks can test particular application semantics. In an exploratory study with ten participants, we investigated how Bifröst influences debugging workflows.
Link to the paper

Geometric Optimization of Microfabricated Silicon Electrodes for Corona Discharge Based Electrohydrodynamic Thrusters
Daniel S Drew, Kristofer S J Pister, Micromachines, Microplasmas issue
In this work, an array of hybrid wire-needle and grid electrode geometries were fabricated and characterized to attempt to minimize both corona discharge onset voltage and thrust loss factor. Statistical analysis of this dataset was performed to screen for factors with significant effects. An optimized emitter electrode decreased onset voltage by 22%. Loss factor was found to vary significantly (as much as 30%) based on collector grid geometric parameters without affecting discharge characteristics. The results from this study can be used to drive further optimization of thrusters, with the final goal of providing a path towards autonomous flying microrobots powered by atmospheric ion engines.}
Link to the paper

First Takeoff of a Flying Microrobot With No Moving Parts
Daniel S Drew, Kristofer S J Pister, MARSS 2017, Best Paper Award Honorable Mention
In this work, we demonstrate an insect-scale robot capable of vertical takeoff using electrohydrodynamic thrust, a mechanism with no natural analogue. The 10mg, 1.8cm by 1.8cm "ionocraft" operates at about 2400 volts and has a thrust to weight ratio of approximately 10. Feasibility of using individually addressable thrusters in a quadcoptor-esque manner for attitude control is demonstrated qualitatively. A combination of design choices in the microfabricated silicon electrodes and a machine-fabricated external fixture allow for reproducible hand-assembly of the microrobot.
Link to the paper

Future Mesh Networked Pico Air Vehicles
Daniel S Drew, Brian Kilberg, Kristofer S J Pister, ICUAS 2017
Taken together, recent advances in microelectromechanical systems, wireless mesh networks, digital circuits, and battery technology have made the notion of autonomous pico air vehicles viable. In this work we describe the core technologies enabling these future vehicles as well propose two possible future platforms. We draw on recent research on high thrust density atmospheric ion thrusters, microfabricated silicon control surfaces, and extremely low mass and power mesh networking nodes. Using the same open-source network implementation as we have already demonstrated in larger UAVs, these flying microrobots will open up a new application space where unobtrusiveness and high data granularity are vital.
Link to the paper

First Steps of a Millimeter-scale Walking Silicon Robot
Daniel S Contreras, Daniel S Drew, Kristofer S J Pister, TRANSDUCERS 2017
We present the first evidence of locomotion from a walking silicon robot based on a two degree-of-freedom robot leg with the largest force and displacement of any electrostatically-driven SOI leg to date. The peak vertical force is five times the weight of the robot. Using a new approach, the robot stands with the chip vertically and has demonstrated its ability to lift itself and move forward while actuating the leg on the ground under tethered power and control. This is the simplest process (2 mask SOI) for making an electrostatic SOI robot that has been demonstrated.
Link to the paper

First Thrust from a Microfabricated Atmospheric Ion Engine
Daniel S Drew, Daniel Contreras, Kristofer S J Pister, MEMS 2017
The bulk of current research in the realm of pico air vehicles has focused on biologically inspired propulsion mechanisms. In this work we investigate the use of electrohydrodynamic thrust produced by a microfabricated corona discharge device as a mechanism to create flying microrobots with no moving parts. Electrodes of various geometries are fabricated from a silicon-on-insulator wafer with a two mask process. Electrical characterization is performed to analyze the effect of inter-electrode gap and emitter electrode width on corona discharge and compare findings to simulation. Outlet air velocity and thrust are directly measured to analyze the effects of collector electrode geometry on performance. A roughly 100 cubic millimeter, 2.5mg thruster is assembled with a thrust to weight ratio exceeding 20.
Link to the paper

The Toastboard: Ubiquitous Instrumentation and Automated Checking of Breadboarded Circuits
Daniel S Drew, Julie Newcomb, William McGrath, Filip Maksimovic, David Mellis, Bjoern Hartmann, UIST 2016
The recent proliferation of easy to use electronic components and toolkits has introduced a large number of novices to designing and building electronic projects. Nevertheless, debugging circuits remains a difficult and time-consuming task. This paper presents a novel debugging tool for electronic design projects, the Toastboard, that aims to reduce debugging time by improving upon the standard paradigm of point-wise circuit measurements. Ubiquitous instrumentation allows for immediate visualization of an entire breadboard's state, meaning users can diagnose problems based on a wealth of data instead of having to form a single hypothesis and plan before taking a measurement. Basic connectivity information is displayed visually on the circuit itself and quantitative data is displayed on the accompanying web interface. Software-based testing functions further lower the expertise threshold for efficient debugging by diagnosing classes of circuit errors automatically. In an informal study, participants found the detailed, pervasive, and context-rich data from our tool helpful and potentially time-saving.
Link to the paper
Workshop Papers

High Power Density Electrohydrodynamic Jet Arrays Using Folded Laser Microfabricated Electrodes
Daniel S Drew, Sean Follmer, Hilton Head 2020
Miniaturized electrohydrodynamic propulsion devices have extremely high power densities due to the small required electrode gap. To lift useful payloads, however, prior work has largely implemented wider total thruster area, effectively decreasing the volumetric power density of the system. This paper shows that through vertical integration of ducted EHD jets we can near linearly increase the propulsive force with number of stages while maintaining high power densities.

Takeoff of a Flying Microrobot With COTS Sensor Payload Using Electrohydrodynamic Thrust Produced by Sub-millimeter Corona Discharge
Daniel S Drew, Kristofer S J Pister, Hilton Head 2018
This paper demonstrates the first flying microrobot using electrohydrodynamic thrusters, or ionocraft, to successfully take off while carrying an onboard commercial sensor package. The 13.6mg, 1.8cm by 1.8cm ionocraft is shown to take off while carrying a 40mg Flex PCB with 9-axis IMU and associated passives while tethered to a power supply. A new emitter electrode design has decreased corona onset voltage by over 30% and takeoff voltage by over 20% from previous efforts. Thrust density scaling with increasing numbers of emitter wires, continued geometric scaling for decreased operating voltage, device lifetime improvement via thin film deposition, and new assembly techniques are all explored.
Link to the paper

Investigation of Atmospheric Ion Thrusters Using Rapid Prototyping Techniques
Daniel S Drew, Joseph Greenspun, Kristofer S. J. Pister, Robotics Science and Systems (RSS):Robot Makers 2014
Electrohydrodynamic (EHD) thrusters, which use ionized air under the influence of an electric field to produce a force, have been investigated for the purposes of flying vehicles for decade. This work focuses on leveraging the precision and speed of rapid prototyping techniques such as 3D printing and laser engraving in order to rigorously investigate this phenomenon at scales relevant to microrobot research.
Link to the paper

Research Dreams
  • "Gnat" robotics
  • The other day I wanted to move a big houseplant of mine to a spot where it would get more midday sun. I'm not home enough during the early afternoon to really remember where the sun shines brightest. What's a simple and cheap way to figure this out? My engineer brain says to prototype some sort of photodiode array with Arduino and log the results... but what if I could just take a handful of tiny robots out of my pocket and throw them into the room? This isn't a problem that requires much intelligence, mobility, or lifetime; all they have to do is spread out in one room and record light every 30 minutes. I won't even pick them up when they're done, I'll let them "self-destruct."
    Flynn, Anita M. "Gnat robots (and how they will change robotics)." (1987).

  • How do humans interact with swarms?
  • I hate when people fly quadcoptors near my head, especially the little ones that make the extremely high pitched rotor noises (must be the primal fear of eye gouging). Just imagine when autonomous swarm technology matures and we have thousands of them flying around at once. Right now the research is heavily focused on industrial and commercial applications, but even then someone is going to have to interact with these swarms. How do you interact with Honda's ASIMO? You can shake its hand. How do you interact with a Boston Dynamics Spot? Maybe pat it on the head. Interacting with a swarm of buzzing insects is out of the realm of human experience.

    I want to use virtual reality as a tool to simulate human interaction with autonomous microrobot swarms. How can a swarm express its intentions? How should it use situational context to modify its own behavior?

  • Big data from lots of small things
  • One estimate is that there are 10 quintrillion insects on earth at any one time- that's 10^19. The trillion-sensor movement as currently conceptualized relies on human installation and maintenance, with industrial pushes largely towards longer device lifetime so humans have to go service motes less often. Let's provide each of these sensor motes with its own mobility platform; we already know from nature that there is an insect to suit every environment and that they have no trouble spreading. Moving beyond the (wildly important) application example of "search and rescue," how can we use these swarms to change the world?
    The future of flying robots - Vijay Kumar from UPenn

Press and Other Publicity
UC Berkeley Grad Slam
Second place finalist in the 2018 Grad Slam with my presention "A Swarm in Every Pocket: Autonomous Microrobots as the Future of Tools"
Release about the finalists