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Steven Charles

Associate Professor, Mechanical Engineering

350J EB

As a biomedical engineer, Dr. Charles investigates how humans control their movements, what goes wrong in movement disorders, and how to use technology to evaluate, assist, or rehabilitate patients with movement disorders. His research draws on knowledge and practices from biomechanics, neuroscience, robotics, and rehabilitation.

Ph.D. Mechanical and Medical Engineering, Harvard-MIT Division of Health Sciences and Technology (HST), 2008.
HST is a unique joint program between Harvard Medical School and MIT that is structured in four phases:

  1. Doctoral training in mechanical engineering at MIT, including qualifying exams
  2. Preclinical medical school coursework totaling roughly half of the coursework required for the M.D. degree
  3. Clinical experiences on the wards of a Harvard-affiliated teaching hospital (condensed version of third-year medical school experience)
  4. Doctoral research

Dissertation: “It’s All in the Wrist: A Quantitative Characterization of Human Wrist Control”
Advisor: Prof. Neville Hogan, Mechanical Engineering, Brain and Cognitive Sciences, MIT

Abstract: My dissertation presents a quantitative characterization of humans’ wrist rotations, paving the way for intelligent robot-assisted rehabilitation of wrist rotations. Using a rehabilitation robot and a motion capture system, I found that wrist rotations exhibit a significant pattern of curvature. Through mathematical models of wrist rotation, I showed that the observed pattern is due to imperfect peripheral execution, not central representation. I went on to demonstrate that the exact cause of the observed pattern, and the main challenge for wrist rotations, is the wrist’s passive stiffness. This result is in striking contrast to arm movements, where interaction torques dominate. However, through studies investigating adaptation, I have also shown that subjects can adapt to dynamic perturbations and revert toward pre-perturbation kinematics, suggesting that wrist rotations are dominated by kinematic control, which is similar to reaching movements.

M.S. Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 2004
Thesis: “Design and Thermal Modeling of a Non-invasive Perfusion Probe”
Advisor: H. Frederick Bowman, Harvard-MIT Division of Health Sciences and Technology

Abstract: Invasive thermodiffusion probes are capable of measuring tissue perfusion accurately, continuously, and in real time. The goal of my master’s thesis research was to create a non-invasive thermodiffusion probe. Creating such a probe involved designing its shape and function to maximize the thermal signal on the one hand and to accurately model perfusion on the other. Using finite-difference models of heat flow through probes and underlying tissue, I showed that by modeling a thin, disk-shaped thermistor probe as a hemisphere of appropriate radius, one can estimate perfusion with sufficient accuracy for clinical use.

B.S. Mechanical Engineering, Brigham Young University, 2001
Magna Cum Laude

Post-doctoral Research Fellow, Johns Hopkins University and Kennedy Krieger Institute, 2008-2010
Advisors: Prof. Allison Okamura and Prof. Amy Bastian

Abstract: Current hypotheses regarding the role of the cerebellum in motor control suggest that the cerebellum holds an internal model of limb dynamics. I proposed and tested an alternative hypothesis, namely that the role of the cerebellum is to control or implement muscle force downstream of any computation of limb dynamics. If this alternative hypothesis is true, cerebellar patients should have difficulty with limb control even in the absence of limb movement. To test this hypothesis, I devised an experimental protocol in which I measured cerebellar patients’ ability to control arm force isometrically, i.e. in the absence of dynamics, and compared their ability to that of healthy subjects. I found that cerebellar patients do indeed have significant difficulty in controlling their arm force isometrically (p = 0.001), indicating that the cerebellum has a more general role than previously thought, including the role of controlling force (even in the absence of movement).

Research Assistant to Prof. Neville Hogan, Newman Laboratory for Biomechanics and Human Rehabilitation, MIT, 2004-2008. Characterized biomechanics and neural control of wrist rotations.

Research Assistant to H. Frederick Bowman, Harvard-MIT Division of Health Sciences and Technology, 2001-2004. Designed and modeled a non-invasive thermodiffusion perfusion probe.

Research Assistant to H. Frederick Bowman and Cardiologist Brian Whisenant, University of Utah Hospital, 2001. Performed non-invasive perfusion measurements in patients.

Research Assistant to Prof. David Clarke, University of California Santa Barbara, Summer 2000. Sponsored by NSF REU program. Performed Raman spectroscopy measurements on gallium nitride semiconductor material.

Research Assistant to Prof. Larry Howell, Compliant Mechanisms and MEMS Research Group, Brigham Young University, 2000. Edited textbook and created software for modeling compliant mechanisms.

Research Assistant to Prof. Ian Hunter, Bio-Instrumentation Laboratory, MIT, Summer 1999. Sponsored by NSF REU program. Characterized evaporation in drug micro-arrays.

Medical Clerkship (4 weeks), Mount Auburn Hospital, Cambridge, MA, 2007. Under the supervision of resident and attending physicians, administered care for five patients, including taking full physical exam and history on admission and daily physical exams, recording progress notes, recommending and executing treatment, and counseling patients and their families; participated in daily medical rounds and training seminars.

Clinical Training (6 weeks), Mount Auburn Hospital, Cambridge, MA, Massachusetts General Hospital, Children’s Hospital Boston, Boston, MA, 2007. Learned to do a full physical exam and take a complete history; performed physical exams and wrote histories for nine patients; observed 3 neurologists in Multiple Sclerosis, Huntington’s disease, and Rett syndrome clinics; shadowed wrist and hand surgeons during office and hospital visits; observed 11 surgeries.