Gregory J. Gerling, Ph.D.

    Associate Professor

    Systems and Information Engineering

    gregory-gerling virginia edu

Greg Gerling     Gerling Lab Logo          

Our Facilities

Laboratory.  Dr. Gregory Gerling's dedicated Fabrication Lab (Lab Space 1) is 500 square feet of staging space, for the rapid fabrication of metals, electronics and silicone/plastics. This area includes an electronics bench (with oscilloscope, function generator, analog/digital converter, power supplies and other prototyping equipment), two mechanical bench workspaces (with milling machine, band saw, and other small power and hand tools), a sink hookup, a fume hood, a small vacuum chamber, and a vacuum pump. This lab is one part of a building dedicated to Systems and Information Engineering researchers, and provides the necessary facilities to work with silicones, metals, and electronics. 

Dr. Gregory Gerling’s dedicated Demonstration and Programming Lab (Lab Space 2) is a 200 square foot computer and demonstration laboratory space for running human psychophysics experiments built after device prototyping, such as the Virginia Prostate Examination Simulator. The psychophysical experiments also utilize the Phantom haptics device, which simulates force-feedback to users, and the custom-built hybrid (computerized and physical) simulators for the prostate and breast palpation exams.  Also within this space is a Dell workstation with 2 GB of RAM which is used for running large finite element simulations.

                          lab 2          
lab 3

Computer.  The lab houses or provides network access to a variety of current-generation computing equipment including modern Windows workstations. All equipment is networked and connected directly to the University backbone and to the Internet. The Department of Systems and Information Engineering also has a considerable amount of supporting software (e.g. programming environments, simulation tools, and statistical packages, etc.) that are available for use.

Office.  The Systems and Information Engineering (SIE) department offers additional office space, which will be utilized as part of this effort. Specifically, faculty and graduate student offices will house the investigators and graduate students.  My office (~120 sq. ft.) is located in Olsson Hall, where resides the administrative office for the SIE department.  Each lab member (graduate student and/or post doc) has a desk in a separate building with access to a shared departmental printer, where Systems and Information Engineering personnel occupies two floors.  The Gerling Fabrication and Demonstration and Programming Laboratories reside in that same building.  There is also a conference room there where teleconferences can be conducted.

Major Equipment 

Spherical indenter.  The spherical indenter was built for use in the clinical setting that can determine ex vivo the elastic modulus of soft biological tissue. The indenter was built to be portable, operable by a clinician, and able to complete 3 to 5 indentations within 15 minutes. The footprint of the indenter rig is 46 cm by 61 cm, which fits on a standard lab bench. The computer terminal is mounted on the upper deck and is accessible by someone 1.63 m tall. The aluminum superstructure weighs less than 23 kg, a load transferable by two persons. The graphical user interface requires the operator enter four parameters: unique patient ID, indentation location, indentation type, and sample thickness at indentation site. The indenter tip is a 12 mm diameter, AISI E52100 steel ball mounted to an aluminum standoff (1.27 cm length, 0.64 cm diameter). The standoff is attached to a load cell (Honeywell, Model Sensotec 11 subminiature, Columbus, OH) with a 44 N maximum load capacity. The load cell is mounted to an aluminum sled which is driven by a motorized linear stage (Newport, Model ILS100, Mountain View, CA) with 100 mm travel and 50 mm/s maximum velocity. It is controlled by a motion controller (Newport, Model ESP300) with 0.0001 mm positioning accuracy. A laptop computer (Lenovo, Model X61 ThinkPad, Morrisville, NC) is used for data acquisition (National Instruments, Model DAQCard-6036E, Austin, TX) and for operating the graphical user interface (National Instruments, LabView 8.5 Professional). Tissue samples were positioned on an aluminum plate attached to two low-profile linear stages (Newport, Model 443) mounted in an X-Y configuration with 50 mm travel and 5 turn/mm positioning resolution. Two types of data are logged, force on load cell and position of linear stage (1x10-6 N and 0.0005 mm resolutions, respectively). The realized sampling rate for the load cell and linear stage are 1 kHz and 9 Hz. To smooth the data from the load cell, a moving average filter is used with a 20-sample, half-width (Smoothing Filter Coefficients Virtual Instrument in LabView Signal Processing Toolkit).


Virginia Prostate Examination Simulator.  The design of the VPES utilizes rubber-like materials to simulate the feel of tissue while using a computer to reconfigure test scenarios and pressure sensors to record finger pressure for immediate feedback and post-performance review. Three to ten instrumented prostate models with accurate size and stiffness are attached to a track system internal to a posterior torso. Their dimensions are 5.5 cm (transverse, width dimension) by 5.0 cm (longitudinal, length dimension). Four to six polyethylene balloons are embedded in each instrumented prostate and filled with water to simulate palpable abnormalities. Deflated balloons are not palpable. The VPES can simulate normal and abnormal prostate conditions including prostatitis (enlarged and boggy inflammation) and carcinoma (small and firm isolated nodule) by utilizing balloons in various configurations of size and location, but similar hardness (~30 Shore A durometers). Balloons of increasing size are named from “A” to “E” and are positioned in different locations for each prostate. The size of the smallest balloon “A” is 0.5 by 0.5 cm, while that of the biggest balloon “E” is 3.0 by 1.5 cm. In addition to simulating all disease states, the VPES simulates each disease state more than once, which leads to a large number of total possible scenarios (>150). Water pressure is delivered via a control box with three printed circuit boards, a water pump, water sensors, and switching valves. Using water pressure and force sensors, respectively, the VPES captures the finger pressure employed on inflated balloons and on the prostate. A change in water pressure denotes that a user has palpated an abnormality, and this information is logged for post-examination analysis. Accompanying the water pressure sensors, force sensors monitor the examiner’s finger on the simulated prostate. Four force sensors (Tekscan, Flexiforce 0-1 lb) are embedded at the base of each instrumented prostate and record the location and magnitude of applied finger pressure.


Columbia University Z-stage Indenter.  We built a mechanical indenter for the Lumpkin Lab (Columbia Universit) to deliver calibrated mechanical displacements to SAI afferents.  This indenter has been used to make measurements of SAI responses that we are now modeling in conference and journal papers.  In summary, families of mechanical displacements are delivered using this custom-built indenter, with stimulus order randomized using atmospheric noise (Random.org). A 3.4-mm diameter (9.2 mm2) MACOR (Corning) filleted cylinder was mounted to a motorized Z-stage driven by a linear actuator (Ultra Motion model D-A.25AB-HT17-2-BR/4) that is wired in parallel to a stepper motor controller (Applied Motion Products 3540i) configured for 2×104 steps per revolution. The indenter has a maximum travel of 50 mm and moves in 0.32-μm increments. Typical stimuli are ≤2 mm and are performed with accelerations ≤1.27 μm/ms2 and average velocities ≤40 μm/ms. Generated pressures under the probe tip range from 1–250 kPa, roughly matching the pressure generated by von Frey filaments of ≤10 mN. A digital signal from the motor controller is sampled to mark the onset and termination of probe movement.  During mechanical stimulation, the applied force is constantly monitored in real time by a load cell (Honeywell model 31) and amplified via an inline amplifier (Honeywell model 0606827-02). The indenter is controlled via custom handheld remote or custom software.  Displacement steps are 5-s in duration and were delivered at 30-s intervals.  Displacement families are performed in 0.1- to 0.2-mm increments between the minimum displacement required to elicit a response and the maximum displacement with forces in the linear range of the force transducer (~1.7 N).


Virginia (Virtual Reality) Chest Tube Simulator.  The chest tube simulator is made up of three components: a 3-D display and virtual environment, two Sensable OMNI force feedback devices, and a chest mannequin.  The virtual operating room is built through the Python programming language and the H3D haptic library (SenseGraphics).  Two force feedback devices with six degrees of freedom are used with three hands-on, haptic interfaces: a pen, a custom-built Kelly clamp, and a custom-built finger constriction device. The chest mannequin component serves to integrate the force feedback devices and provide a focal point for the user.  To control both the force feedback device and graphics rendering, the simulator uses the open source development platform H3D, which is built on the C++ language and OpenGL.  X3D, a second open source platform based on XML, works in conjunction with H3D to represent and communicate with the 3D virtual models.  While X3D defines the scene-graph and 3D objects, H3D provides support for force feedback interaction with virtual elements.