Medical robotics and computer-integrated surgery are the link that enables closed loop medicine by using real-time feedback to guide a surgical procedure. As part of our research, we are integrating interactive Magnetic Resonance Imaging (MRI) with the interventional procedure. Applications include stereotactic neurosurgery for deep brain stimulation (DBS) lead placement for Parkinson's Disease and brachytherapy seed implantation for prostate cancer therapy.


MRI Compatible Robotics:

Magnetic Resonance Imaging (MRI) is an excellent imaging modality for many conditions, but to date there has been limited success in harnessing this modality for the guidance of interventional procedures. MRI is an ideal interventional guidance modality: it provides near real-time high-resolution images at arbitrary orientations and is able to monitor therapeutic agents, surgical tools, biomechanical tissue properties, and physiological function. At the same time, MRI poses formidable engineering challenges by severely limited access to the patient and high magnetic field that prevents the use of conventional materials and electronic equipment. We have developed: a modular MRI robot control system, approaches to actuating piezoelectric motors, optical force sensors, in-bore teleoperation, and surgical systems for stereotactic neurosurgery and percutaneous prostate cancer interventions.


MRI Robot for Precision Deep Brain Stimulation Probe Placement

MRI Robot for Neurosurgery

MRI Compatible Neurosurgery Robot

Robotic Deep Brain Stimulation for Parkinson's Disease Treatment

Direct MR image guidance during deep brain stimulation (DBS) insertion offers many benefits; most significantly, interventional MRI can be used for planning, monitoring of tissue deformation, real-time visualization of insertion, and confirmation of placement. The accuracy of standard stereotactic insertion is limited by registration errors and brain movement during surgery. With real-time acquisition of high-resolution MR images during insertion, probe placement can be confirmed intra-operatively. Direct MR guidance has not taken hold because it is often confounded by a number of issues including: MR-compatibility of existing stereotactic surgery equipment and patient access in the scanner bore. The high resolution images required for neurosurgical planning and guidance require high-field MR (1.5-3T); thus, any system must be capable of working within the constraints of a closed, long-bore diagnostic magnet. Currently, no technological solution exists to assist MRI guided neurosurgical interventions in an accurate, simple, and economical manner. The objective of our research is to make conventional diagnostic closed high-field MRI scanners available for guiding deep brain stimulation electrode placement interventions for treatment of Parkinson's Disease and other neurological disorders including severe depression and Alzheimer's Disease. Our approach is to employ an MRI-compatible robotic assistant for guiding DBS electrode insertion under direct, real-time MR image guidance. The system will allow interactive probe alignment under real-time imaging in standard diagnostic high-field MR scanners. Use of a robotic assistant will minimize the potential for human error and mis-registration associated with the current procedure and will better address the practical issues of operating in an MR scanner bore.


Piezoelectrically Actuated MRI-Compatible Robot for Prostate Interventions

MRI has potential to be a superior medical imaging modality for guiding and monitoring prostatic interventions. MRI can provide high-quality 3D visualization of prostate and surrounding tissue. However, the benefits can not be readily harnessed for interventional procedures due to difficulties that surround the use of high-field (1.5T or greater). The strong magnetic field prevents the use of conventional mechatronics and the confined physical space makes it extremely challenging to access the patient. We have designed a robotic assistant system that overcomes these difficulties and promises safe and reliable intra-prostatic needle placement inside closed high-field MRI scanners.


Modular MRI Compatible Robot Controller

Modular MRI-Compatible Robot Controller

MRI Compatible Robot Controller

The unavailability of robot control interfaces that are compatible with the MRI environment has severely limited the ability to do research in the field. The high cost of entry into MRI robotics has been primarily due to the need for each researcher to develop and evaluate their control system in the scanner. We have developed an MRI compatible robot controller that sits in the scanner room without interfering with scanner imaging. The controller is modular and allows many different inputs and output and communicates to a high level planning and navigation software workstation through fiber optic connections.


Development and Evaluation of MRI-Compatible Actuators

Traditional actuators are often contraindicated by the strong magnetic and electric fields present in the MRI scanner bore. Further, it is critical that the devices not introduce noise or distortion into the acquired images. We are evaluating different actuator schemes including pneumatics and piezoelectric actuators. We are investigating ways of optimizing piezoelectric motors for MR-compatibility and developing high-accuracy pneumatic control systems.


Development and Evaluation of MRI-Compatible Sensors

Traditional sensors in robotics include force and positioning sensing. However, off-the-shelf sensors are not suiatable for use in MRI due to the potential for image degradation, malfunction, or safety issues. We are evaluating and developing sensors to be used in the MR environment. The current focus is on optical techniques for force and position sensing that do not compromise image quality and will allow for haptic feedback during MRI-guided interventions.


Pneumatically Operated MRI Robot for Transperineal Prostate Diagnosis and Treatment

Pneumatic Robot for Prostate Surgery

MRI Compatible Needle Placement Robot

MRI has potential to be a superior medical imaging modality for guiding and monitoring prostatic interventions. MRI can provide high-quality 3D visualization of prostate and surrounding tissue. However, the benefits can not be readily harnessed for interventional procedures due to difficulties that surround the use of high-field (1.5T or greater). The strong magnetic field prevents the use of conventional mechatronics and the confined physical space makes it extremely challenging to access the patient. We have designed a robotic assistant system that overcomes these difficulties and promises safe and reliable intra-prostatic needle placement inside closed high-field MRI scanners.


Clinically Focused MRI Robot Control Architecture

Clinical Robot Control Architecture

MRI Robot Controller Architecture

We have developed a clinically focused robot control architecture to support our MRI-compatible robotic systems. The work includes custom hardware, communication protocols, and user interfaces. Safety and reliability are incorporated while ensuring a clinically appropriate workflow. The system is configured for clinical trials with the MRI-guided Prostate Biopsy and Brachytherapy robot.


Surgical Robotics Technology:

Surgical robots enables us to take advantage of intraoperative imaging to perform closed loop control, and can also be used to generate a sense of telepresence within the body. Although much of the focus in the AIM Lab is on MRI-compatible surgical systems, we are also pursuing various other enabling technologies for surgical robotics. Some of our research areas include: robot control software architecture, integration of haptic feedback, and teleoperation. As part of this work, we have developed a system with integrated force sensing capable of manipulating standard daVinci surgical tools using a haptic interface for investigating different approaches to providing force feedback to the surgeon. We have also developed a framework for robot control based upon the open source Java OpenIGTLink libraries.


Software Interfaces and Communication Protocols for Surgical Robots - OpenIGTLink

OpenIGTLink Interface

OpenIGTLink Concept

With increasing research on system integration for image-guided therapy (IGT), there has been a strong demand for standardized communication among devices and software to share data such as target positions, images and device status. We have worked on integration and development of components for OpenIGTLink, a standardized mechanism to connect software/hardware through the network for image-guided therapy (IGT) applications.


daVinci Surgical Robot Robot Research System (dVRK)

daVinci Robot Research System

WPI dVRK System

We have a research version of the Intuitive Surgical daVinci Robot. The daVinci Research Kit (dVRK) consists of a surgeon's console where the surgeon controls the robot and a patient side console which performs the surgical intervention. The system uses custom-developed open-source hardware and software to enable full control over the robot.


Augmented Reality Procedural Guidance:

Image-guided percutaneous needle-based surgery has become part of routine clinical practice in performing procedures such as biopsies and injections. Image-guided needle placement procedures in CT/MR benefit from an accurate and effective augmented reality (AR) system. We have developed an MRI-compatible 2D augmented reality image overlay device to guide needle insertion procedures. This approach makes diagnostic high-field magnets available for interventions without a complex and expensive engineering entourage. In preclinical trials, needle insertions have been performed in the joints of porcine and human cadavers using MR image overlay guidance; insertions successfully reached the joint space on the first attempt in all cases. We have also developed a training system to educate and evaluate users of the system.


MR Image Overlay for Joint Arthrography

MRI Image Overlay

MRI Image Overlay

Magnetic Resonance Imaging (MRI) provides great potential for planning, guiding, monitoring and controlling interventions. MR arthrography (MRAr) is the imaging gold standard to assess small ligament and fibrocartilage injury in joints. In contemporary practice, MRAr consists of two consecutive sessions: 1) an interventional session where a needle is driven to the joint space and MR contrast is injected under fluoroscopy or CT guidance, and 2) A diagnostic MRI imaging session to visualize the distribution of contrast inside the joint space and evaluate the condition of the joint. Our approach to MRAr is to eliminate the separate radiologically guided needle insertion and contrast injection procedure by performing those tasks on conventional high-field closed MRI scanners. We propose a 2D augmented reality image overlay device to guide needle insertion procedures. This approach makes diagnostic high-field magnets available for interventions without a complex and expensive engineering entourage. In preclinical trials, needle insertions have been performed in the joints of porcine and human cadavers using MR image overlay guidance; insertions successfully reached the joint space on the first attempt in all cases.


Training and Evaluation System for Image-Guided Therapy - Perk Station

Perk Station

The Perk Station

Image-guided percutaneous needle-based surgery has become part of routine clinical practice in performing procedures such as biopsies and injections. Image-guided needle placement procedures in CT/MR benefit from an accurate and effective augmented reality (AR) system. In order to operate the system the user has to be trained. Therefore, we have developed a laboratory validation and training system for measuring operator performance under different assistance techniques for needle-based surgical guidance systems named "The Perk Station." Three techniques are fitted in this training suite: the image overlay, bi-plane laser guide, and traditional freehand techniques. An electromagnetic tracking system is applied in the validation system. The Perk Station, an inexpensive, simple and easily reproducible surgical navigation workstation for laboratory practice incorporating all the above mentioned functions in a "self-contained" unit, is introduced.


Assistive Robotics:

We are developing various assistive and human interaction robots in the AIM lab. One research thrust is focussed on providing assistance to disabled persons through the use of rehabilitation and assistive devices. One focus of this research is an actuated glove for stroke rehabilitation assistance - the glove is cable actuated and controlled through various means including EMG signals to assist in training a stroke victim's grip. The other primary research thrust is robotic devices for interacting with children that have pervasive developmental disorders such as autism. Robot can be used as a way to enhance the therapy a child receives and also extend the amount of time with which they receive interaction. The robot can interact with the child both autonomously and through telepresence to help augment their course of therapy as well as log and quantify their progress.


Humanoid Robot for Autism Interventions in Children - PABI

Autism Therapy Robot

PABI © - Penguin for Autism Behavioral Interventions

The Penguin for Autism Behavioral Interventions (PABI)© developed in the WPI Automation and Interventional Medicine Lab will help children socialize and assist in applied behavior analysis (ABA) therapy. The cartoon-like embodiment will look at children, make facial expression and utterances, track eye contact, and stimulate a social response. PABI is small enough in size that the child can hold it, creating a physical connection which may enhance feelings of affection toward the robot, prolonging the child's interest in it. The modest size allows for easy transportation of the robot to increase generalization of social skills across settings. The ability of the robot to monitor gaze and social cues may provide diagnostic utility. The robot can be used as an autonomously acting "toy" to interact with or in semi-autonomous remote control mode where a clinician can control the robot's motions while receiving video and audio streams.


Cable Actuated Exomusculature Glove for Stroke Rehabilitation and Assistance

Stroke Rehabilitation Glove

Stroke Rehab Glove

The project is to develop a device to assist people with limited hand movement to be able to open and close their hand to accomplish simple tasks using multiple operating possibilities. The glove can support EMG-controlled active assistance, active resistance, and pre-programmed motions.


Wearable Exo-musculature Soft Robots

Wearable Exo-musculature Soft Robots

Wearable Exo-musculature

The goal of our work in soft robotics is to develop a wearable rehabilitation device that would allow patients suffering from hemiparesis to perform repetitive motion therapy in their homes. This therapy is commonly used in restoring lost motor skills by helping the brain rebuild neural pathways lost as a result of disease or trauma such as stroke. In removing the need for a physical therapist to conduct these exercises, the patients would be able to devote more time to their therapy at a lower cost while achieving a greater level of independence.

Robots in Education:

WPI has developed a new bachelors degree program in Robotics Engineering. As part of this effort we are developing robotic systems applicable to teaching the fundamentals of robotics as well as a corresponding new curriculum. We have developed educational robot control electronics for embedded systems development, motor control, and sensor interfacing. We have also developed a manipulator arm and a mobile platform, both of which can be operated using the same control electronics. These systems have been successfully used to teach the junior level undergraduate Robotics Engineering courses at WPI.


Educational Platform for Robotics - Development Board, Robotic Manipulator Arm and Mobile Platform

Robots in Education - EduArm Manipulator

Custom arm and control hardware for RBE 3001

No one hardware platform provides all of the tools required to teach a robotics engineering curriculum. We have developed are developing a unified platform specifically designed for multidisciplinary undergraduate robotics education. We have developed a set of instructional equipment including the RBE development board, a manipulator arm and a mobile platform.


Undergraduate Research Projects:

All undergraduates at WPI must complete a Major Qualifying Project known as the MQP and an Interactive Qualifying Project known as the IQP. The IQP generally relates to societal issues, and the AIM lab has hosted projects focussed on evaluating the perceptions of surgical robotics among patients, practitioners, and the general public. The MQP is typical an almost year-long design project. In the AIM Lab, we host many projects, most of them directly related to our core research areas and in close collaboration with graduate students. Please see some of our current and past projects. If you are a student interested in participating or a company looking to sponsor a project, please contact Prof. Fischer.


IQP - Perceptions of Robots in Surgery

The goal of this work is to study the conceptions about the use of robotis in surgery. We are specifically investigating the differences in these perceptions among different patient and medical professional populations. The work is primarily focussed on use of the da Vinci Surgical System.


MQP - Hybrid Pneumatic-Hydraulic Actuator for MRI Robots

A linear pneumatic-hydraulic MRI robot actuator was designed as a modular solution to precision motion in a medical MRI environment. The implementation of this non-ferrous and nearly completely non-metallic linear driver mechanism gives an operator the ability to place grippers, sensors, syringes, and other medical instruments with an extraordinary level of flexibility and precision. Its modular design allows for rapid prototyping of robotic systems.


MQP - Force Sensing and Haptic Feedback for Robotic Surgery

The goal of this research was to develop a force sensing module capable of integrating with the da Vinci system and provide the operator with a representation of tool-tissue interaction forces. dditionally, our aim was to develop a test platform for evaluating and implementing haptic feedback and telesurgery techniques. An industrial robot was fit with a spherical wrist and an embedded Linux control system allowing the surgical tool to be articulated about a remote center.


MQP - Development of a Humanoid Robot for Autism Interventions in Children

Autism Robot

PABI © - Penguin for Autism Behavioral Interventions

This project is focused on developing a compact, intrinsically safe humanoid robot for interaction with Autistic children. The robot will be able to be used for treatment and assessment.


MQP - Development of a Robotic Telesurgery System (SASHA)

The goal of this project is to develop a robotic system for performing surgery. This work builds upon previous efforts to turn an industrial robot into a simulated daVinci robot and incorporating torque sensors. The goal is to develop a compact robotic arm that can manipulate daVinci tools from a remote interface, sense interaction forces, and feed those forces back to the operator.


MQP - Hierarchical Swarm Robots

Hierarchical Swarm Robots

Swarm

The basis for this idea is that with current implementations of swarm robotics there is an overall trend where all the robots in the swarm are the same in terms of processing power, design, and computational ability. Generally they have the same sensors and chips, and designing therefore it is a micro world where everyone is equal. In reality, that is nearly never the case and it is much more likely the problem is presented via a hierarchy system. As you increase in level of the hierarchy, the overall knowledge, processing power, and reasoning increases drastically. With this application of a swarm, behaviors that closely mimic real life situations can be recreated to a high degree of accuracy.


MQP - Robot Modeling and Controller Development

Robot Modeling and Controller Development

We have a pair of 4-axis high-speed industrial robots that were recently acquired. The robots have integrated position sensing and are powered by DC servo motors. This project is focused on a full system development of a controller for these robots from scratch. Components of the project will include: 1) modeling the kinematics and dynamics of the robots, 2) developing custom hardware to interface with the robot connections, 3) developing the controller electronics, 4) implementing low-level controllers that allow for joint level and Cartesian position control, velocity control, and force control, and 5) developing an interface to the robot. The endpoint of the project is a robot controller suitable for use as an active research platform. Other related projects include development of end effectors and control algorithms (specifically ones taking advantage of a pair of identical robots working together on a common task).


MQP - Development of a Surgical Robot Manipulator Arm

The goal of this project is to develop a robotic system for performing surgery. This work builds upon previous efforts to simulate the daVinci surgical robot and incorporating sensors. The goal is to configure a robotic arm that can manipulate daVinci tools from a remote interface, sense interaction forces, and feed those forces back to the operator through a haptic master.


MQP - PRiSM Pneumatic Stepping Motor

Pneumatic Stepping Motor

PRiSM Pneumatic Motor

This project is focussed on developing a pneumatic stepping motor with a primary application of MRI-compatible robotics. The proposed actuator design, known as the PRiSM, uses directed pneumatic pressure to generate rotational motion. To confirm the validity of this idea, multiple tests were designed and conducted. These tests showed that, at 60psi, the PRiSM can operate open-loop with an angular velocity of 7deg/s, while exerting a torque of 435N/mm. Optimized conditions yielded an overall maximum angular velocity of 178deg/s and an overall maximum torque of 747N/mm.


MQP - Exoskeleton Assistive Glove (RoboHand)

Exoskeleton Assitive Glove

The project is to develop a device to assist people with limited hand movement to be able to open and close their hand to accomplish simple tasks using multiple operating possibilties.






MQP - Stent Design for Percutaneous Cardiac Valve Placement

The goal is to design a self-expanding Nitinol stent with features to enable attachment to a polyurethane valve, facilitate deployment and repositioning within the aortic annulus. The design was performed in collaboration with Nitinol stent manufacturers, private consultants, and surgeons.

MQP - Guest Orientation, Assistance, and Telepresence (GOAT) Robot

GOAT Telepresence Robot

GOAT Robot

The Guest Orientation, Assistance, and Telepresence (GOAT) Robot will act as a tour-guide or escort at the WPI Campus. GOAT will provide live or telepresence assistance to prospective students as well as academic, corporate, official, and other guests. Users will interact with the robot through a combination of a touch-screen interface, voice, and gesture commands. The robot will guide visitors to destinations and be capable of providing video tour information. It will also be able to serve as a telepresence system for medical and home care environments.



MQP - Assistive Exo-musculature Orthotic Elbow Brace

The goal of this project is to assist patients with impaired movement and to regain control of their arm. A robotic brace was developed to assist with movement, using signals generated from the user's muscles to drive the arm.


MQP - Software Architecture For A Humanoid Robot For Autism Spectrum Disorder Interventions In Children

This project is focused on developing an extensible distributed system architecture a compact, intrinsically safe humanoid robot for assessment and therapy of children with pervasive developmental disorders.


MQP - Exomuscular Sleeve for Upper Limb Stroke Rehabilitation

The aim of this project was to develop an exomuscular arm that could be actuated through a system of Bowden cables linked to precision DC motors housed in an actuation platform. The system assists and controls flexion and extension of the five fingers and the elbow, as well as pronation and supination of the wrist. Through a sensor array located throughout, a feedback system is able to collect quantitative data on position and pressure, and control all degrees of freedom utilizing this data and several on-board processors.


MQP - Indoor Navigation and Manipulation using a Segway RMP Platform

The goal of this project was to work with a Segway RMP, utilizing it in an assistive-technology manner. This encompassed navigation and manipulation aspects of robotics. The robot was programmed to accomplish semi-autonomous multi-floor navigation through the use of the navigation stack in ROS (Robot Operating System), image detection, and a user interface. The robot can navigate through the hallways of the building, using the elevator to travel between floors. The robotic arm was designed to accomplish basic tasks, such as pressing a button and picking an object up off of a table.


MQP - PhleBot: The Robotic Phebotomist

The goal of this project is to develop a compact robotic phlebotomist. Automation of this task by a robotic appliance will greatly expedite clinical procedures while also achieving process consistency. The project aims to design, test and realize a market ready device capable of automatically locating a suitable vein and positioning a needle in it, ready to extract blood.


MQP - Smart Socket: Soft Robotic Prosthetic Socket

The purpose of this project is to develop a socket for a lower limb prosthetic using electrical, biomechanics and robotics engineering concepts. This socket will be able to adapt dynamically to the user's environment and motion as well as provide comfortable stability. The project will incorporate both internal physiological sensing as well as external physical sensing.


MQP - Humanoid Robot for Autism Therapy

The purpose of this project is to further develop a compact, intrinsically safe humanoid robot for interaction with children having Pervasive Developmental Disorders (PDDs). The robot will be able to be used for treatment and assessment.


Past Research:

Prof. Fischer received his Ph.D. from Johns Hopkins University as part of the NSF Engineering Research Center for Computer-Integrated Surgical Systems and Technology (ERC-CISST) in the Laboratory for Computational Sensing and Robotics (LCSR). Some of sis previous work includes: MRI-compatible pneumatic robotics, image overlay guidance, electromagnetic tracker characterization and optimal tool design, smart sensing surgical instruments, and steady hand guided robot control.


Electromagnetic Tracker Navigation and Calibration

Electromagnetic Tracker Navigation

Aurora EM Tracker Calibration

Developing electromagnetically (EM) tracked tools can be very time consuming. Tool design traditionally takes many iterations, each of which requires construction of a physical tool and performing lengthy experiments. We propose a simulator that allows tools to be virtually designed and tested before ever being physically built. Both tool rigid body (RB) configurations and reference RB configurations are configured; the reference RB can be located anywhere in the field, and the tool is virtually moved around the reference in user-specified pattern. Sensor measurements of both RBs are artificially distorted according to a previously acquired error field mapping, and the 6-DOF frames of the Tool and Reference are refit to the distorted sensors. It is possible to predict the tool tip registration error for a particular tool and coordinate reference frame (CRF) in a particular scenario before ever even building the tools.


Sensing Surgical Instruments

Sensing Surgical Instruments

'Smart' Retractor

Gaining access to a surgical site via retracting neighboring tissue can result in complications due to occlusion of the tissue blood supply resulting in ischemic damage. By incorporating oxygenation sensors on the working surfaces of surgical retractors and graspers, it is possible to measure the local tissue oxygen saturation and look for trends in real-time. Further, by measuring tissue interaction forces simultaneously, we can further augment the information available to the surgeon. The sensors provide a means for sensory substitution to help compensate for the decreased sensation present in minimally invasive laparoscopic and robotic procedures that are gaining significant popularity. Sensing surgical instruments will allow for safer and more effective surgeries while not interfering with the normal workflow of a procedure.


Robotic Ultrasound and Liver Ablation

Robotic Ultrasound and Liver Ablation

Dual Arm System

There has been increased interest in minimally invasive ablative treatments that typically require precise placement of the ablator tool to meet the predefined planning, and lead to efficient tumor destruction. Standard ablative procedures involve free hand transcutaneous ultrasonography (TCUS) in conjunction with manual tool positioning. Unfortunately, existing TCUS systems suffer from many limitations and results in failure to identify nearly half of all treatable liver lesions. Freehand manipulation of the ultrasound (US) probe and ablator tool critically lacks the level of control, accuracy, stability, and guaranteed performance required for these procedures. Freehand US results in undefined gap distribution, anatomic deformation due to variable pressure from the sonographer's hand, and severe difficulty in maintaining optimal scanning position. In response to these limitations, we developed a dual robotic arm system that manages both ultrasound manipulation and needle guidance. We have performed a comparative performance study between robotic vs. freehand systems for both US scanning and needle placement in mechanical and animal tissue phantoms.


Steady Hand Guided Aneurysm Clip Applier

Steady Hand Guided Aneurysm Clip Applier

Steady Hand Robot

Steady hand guidance provides high accuracy motion while keeping the surgeon in contact with the surgical instrument. Force sensors are applied between the instrument and the robot, and as the surgeon applies forces to the instrument, the robot move accordingly. Tremor reduction, force scaling, and virtual fixtures can be applied to enhance control. This application uses steady hand guidance to precisely place brain aneurysm clips. The system was demonstrated and received good feedback at the CNS Conference in Denver, CO.


CT Guided Intra Cranial Hemorrhage(ICH) Evacuation

CT Guided Intra Cranial Hemorrhage(ICH) Evacuation

Robotic ICH Removal

We developed a robotic system for rapid removal blood from the brain after a bleeding event resulting in blood in the ventricles or brain parenchyma. The procedure is performed inside a CT scanner. A hematoma evacuator is aligned with the target "out-of-plane", with the use of a couch-mounted 2-DOF remote center of motion (RCM) robot. The robot is calibrated to CT image space with pure image based out-of-plane stereotactic registration. The system is frameless and the patient is secured in treatment position in a non-invasive manner. We achieved excellent out-of-plane tool placement accuracy in mechanical phantoms (1.0 mm) and demonstrated the workflow on human cadaver.

Fields of Research