Senior R&D Engineer - Massachusetts Materials Technologies

MMT, a pioneering company specializing in non-destructive test (NDT) services, merges hardware and software solutions to ascertain material strength through material verification. I was brought onboard to steer the design and development of their second product, marking a groundbreaking venture into additional NDT services for the industry. My role primarily entailed transforming an existing functional prototype into a portable testing apparatus that not only reduced in size and weight but also embraced modularity to facilitate multiple modules and ensured portability.

I spearheaded this challenge by formulating mechanical and electrical requirements for the project, and employing Solidworks for 3D CAD modeling to conceptualize new designs, harmonizing them with established mechanical and functional specifications. Furthermore, I took the initiative in procuring electrical components, including stepper motors, encoders, drivers, and controllers, while also advocating the most suitable software platform for the development of the testing infrastructure.

Product Evaluation Researcher - Bentley University

In my tenure at Bentley, I managed a collaborative effort dedicated to the evaluation of a market-available wearable haptic device, result of a partnership between Bentley and start-up ecosystem. The project’s ambit extended to assessing a spectrum of vibrotactile actuators across multiple scenarios, with an aim to identify the actuator type that delivered peak performance. Given that the device was designed for real-world application, experiments were outlined to evaluate its efficacy in ecological environments, to ensure it can provide augmented situational awareness to users.

In my capacity as a Post-Doctoral Researcher, my responsibilities spanned across the comprehensive design of experiments and testing plans. Additionally, I undertook the conduction of experiments and engaged in rigorous data analysis, culminating in the compilation of findings in both quarterly reports and academic publications, thereby ensuring the study results were well documented and communicated. The product evaluation findings led to recommendations for actuator replacement, enhancing the efficiency of haptic cues received by users.

Senior Thermal Haptic Engineer - Embr Labs

Embr Wave 2: A Comprehensive Approach to Wearable Medical Device Evaluation

Embr Wave 2 stands out as a pivotal wearable medical device designed to provide hot flash relief for women undergoing menopause and individuals experiencing hot flashes due to various medical conditions. My role encompassed both quantitative and qualitative evaluations of the product performance, scrutinizing its thermal functionality and user-related performance metrics.

In one notable project, I spearheaded the development of a testing infrastructure, enabling precise device and user tests within a stringently controlled environment. This framework aimed to meticulously characterize device performance metrics alongside user response evaluation. My responsibilities enveloped the implementation of mechanical, electrical, and software requirements for the test fixture, with a particular emphasis on actualizing the electrical and software specifications. Furthermore, I facilitated effective communication and collaboration within the team to realize the mechanical development aspects, ensuring a well-rounded approach to the testing infrastructure's establishment.

In a separate initiative, I took charge of developing a statistical analysis toolbox using MATLAB App Designer, engineered for swift, scalable data visualization, and derivation of fundamental metrics. This tool was integral in illuminating the team regarding the device and user performance under varied testing conditions, thereby contributing to informed, data-driven decision-making processes across our projects. As an interdisciplinary engineer, I navigated diverse roles—conducting various tests to ascertain product performance under distinct environmental and functional conditions, and serving as the liaison between usability and clinical teams to develop user surveys and conduct related data analysis to make informed decisions regarding product improvements.

REED Lab - University of South Florida

Can we change thermal sensation without changing the temperature? 

Approach:

In this research, a new approach was taken to create a constant cooling/heating perception where the average skin temperature does not change over the skin. This thermal perception was created using asymmetric behavior of thermal perception for cold and heat skin receptors. The testing equipment was a wearable arm-worn device consisting of 12 arrays of thermoelectric devices enabling creation of dynamic thermal patterns on the skin.

Results:

In our study, asymmetric thermal patterns created a counter-intuitive thermal sensation where cooling/heating thermal patterns created heating/cooling perceptions. We hypothesize that this effect is due to the thermal summation property of the skin receptors. 

How well can we remember things that we feel with our skin? What about the things that we see? Can haptic memory reinforce visual memory?

Approach:

How individuals retain sensory information relative to the sensory channel needs to be better investigated. This research studies the contribution of spatial and modality information on retaining visual and haptic cues. The theme of the experiment is similar to Simon Says memory game. Participants must retain a series of haptic or visual cues and repeat them in the same order using the buttons on a custom-built user interface. In some conditions, they needed to rely on the location of the stimuli, whereas, in other conditions, they needed to retain the modality of the stimuli and respond based on the messages shown on screens.

Results:

The results indicated that participants retained longer sequences when spatial information was present than the modality information. In terms of modality comparison, their performance was superior in visual conditions than the haptic conditions. In this task, the shape of the generated spatial patterns by the cues played an essential role in how one performed. Consequently, a  difficulty ranking system for different spatial patterns was developed to evaluate their performance based on self-report and experimental data. 

The results of this research are published in IEEE Transaction on Haptics.

How temperature can affect emotions?

 Approach:

There is evidence about the contribution of temperature on the emotions. Heat can elicit anger, while cold can elicit calmness. Based on this idea and related research in the field of psychology, we decided to investigate the effect of temperature on emotions where participants are unaware of the purpose of the study while receiving thermal stimuli on the back of the neck through a wearable haptic device. Another distinction of this study was the presence of a control temperature condition (neutral temperature). Using self-report methods such as Self-Assessment Manikin (SAM) and Geneva emotion wheel, the emotional ratings of 120 individuals were measured. Individuals reported their emotions after viewing images from the IAPS image library while experiencing cold, neutral, or hot temperature conditions using a custom-built wearable thermal device. Participants reported their emotions using valence and arousal components of the emotion using SAM and reporting the verbal representation of their emotions on the Geneva emotion wheel.

Results:

Study results demonstrated that temperature changes the arousal levels of the emotions. Cold and hot temperatures increase the arousal ratings of the images compared to the neutral. Valence ratings were not affected by the applied temperature. 

The results of this research is submitted and under review by Psychological Science.

Does the representation of perceived temperatures decay over time?

 Approach:

It is demonstrated that sensory memory of visual and auditory information decay over time. However, there is no information about this decay rate for thermal sensory information. A system of thermoelectric devices, controllers, touch sensors, and push buttons was developed to evaluate the thermal discrimination ability of individuals under certain temporal circumstances. For this goal, a discrimination task with a staircase method between two non-zero thermal stimuli.the  was employed to evaluate the effect of Inter-Stimulus Interval (ISI) on thermal discrimination ability (JND).

Results:

We found that JND at ISI=0s was 3.10 °C and increased by 11.9% and 21.2% at JND ISI=3s and JND ISI=9s, respectively. Statistical analysis revealed that ISI had a statistically significant effect (p < 0.05) on thermal perception in our task.

The results of this research are published in IEEE Transaction on Haptics.

What Is an Accurate Representation of Underlying Mechanism of Thermal Grill Illusion?

 Approach:

In this study we are aiming to obtain a more accurate understanding of the biological mechanism behind thermal grill illusion (TGI) by designing an experimental setup where TGI is elicited applying different thermal patterns.

Hypothesis:

We hypothesize that TGI induced pain is created by a combination of these two methods. We expect that the results will demonstrate which one has a more dominant role in the process.

Haptics and Robotics Lab- Bogazici University

How does providing sensory substitution feedback assist position/force coordination in a dynamic finger flexion task?

In this project, a simulated spring buckling test was implemented to evaluate how providing artificial proprioception feedback can affect successful performance of a highly dynamic task where participants needed to interact with a virtual compression spring without buckling of the spring. Participants interacted with a combination of two 2-DOF robotic manipulators and a force sensor to interact with a virtual spring developed using SOFA simulation. Participants were receiving a combination of position, force, and vibration feedback on their contralateral arm depending on the condition of the experiment. The task was to compress the spring to a point without buckling the virtual spring. This task highly required coordination of applied force and position. 

I spearheaded the design, development, and fabrication of CAD models, utilizing machining and 3D printing tools for part production. My responsibilities also extended to the implementation of electromechanical components, encompassing the selection of motors, encoders, and motor controllers. Generating an realistic model of the physical spring was another challenge tackled in this project. The setup was manipulated via two Arduino Mega devices, interfacing with a C++ based program through a serial port. This higher-level program handled the movement of the virtual spring, reading force sensor values via a NIDAQ card, and managing the compression of the virtual spring. Conversion of position input to force feedback and force input to position feedback was performed by implementing impedance and admitance control methods, respectively.    

Publications:

• Hojatmadani, Mehdi, Benjamin Rigsby, and Kyle B. Reed. "Time Delay Affects Thermal Discrimination." IEEE Transactions on Haptics 15.2 (2022): 451-457.

• Hojatmadani, Mehdi, and Kyle B. Reed. "The Role of Spatial and Modality Cues on Visual and Haptic Memory." IEEE Transactions on Haptics 15.1 (2021): 154-163.

• Hojatmadani, Mehdi, and Kyle Reed. "Asymmetric cooling and heating perception." International Conference on Human Haptic Sensing and Touch Enabled Computer Applications. Springer, Cham, 2018. 

• Hojatmadani, Mehdi, and Evren Samur. "Contribution of artificial proprioception on a dynamic finger flexion task." Turkish Journal of Electrical Engineering & Computer Sciences 27.1 (2019). 

• Hojatmadani, Mehdi, et al. "Heat Flux Characteristics of Asymmetrically Heated and Cooled Thermal Stimuli." ASME International Mechanical Engineering Congress and Exposition. Vol. 58431. American Society of Mechanical Engineers, 2017. 

• Madera, Coralis, et al. "Thermal perception of skin using optical projections." ASME International Mechanical Engineering Congress and Exposition. Vol. 58431. American Society of Mechanical Engineers, 2017. 

• Manasrah, Ahmad; Hojatmadani, Mehdi; Guldiken, Rasim; Reed, Kyle. "Computational Analysis of Asymmetrically Applied Hot and Cold Stimuli." Vol. 11. International Journal of Engineering Research and Innovation, 2020.