PRE2020 4 Group8

Team

Members	Student ID	Faculty	E-mail
Ismail Elmasry	1430807	Mechanical Engineering	i.elmasry@student.tue.nl
Ilse Doornbusch	1020872	Psychology and Technology	i.s.doornbusch@student.tue.nl
Amin Mimoun Bourass	1486764	Automotive	a.mimoun.bourass@student.tue.nl
Maud Kunkels	1320025	Industrial Engineering	m.f.kunkels@student.tue.nl

Logbook

The logbook and task division of the team can be found on the page Logbook Group 8

Introduction

On our google drive map we work on our progress.

Microrobots are defined as untethered robots of a size significantly small that are able to move around the body in order to fulfill tasks such as sensing, material removal or targeted therapy. In this report, the focus is placed on medical microrobots that will be used for the circulatory system inside the body. This system consists of the heart and the vessels and it is meant for carrying blood around. Since almost every part in a body can be reached by blood through the vessels, it is a very relevant topic to do research on and to innovate robotic technologies that can improve its working. That is why this report will discuss the use of microrobots for the circulatory system. The functions that such kinds of robots can fulfill are numerous, but the focus will be placed on targeted therapy and telemetry. With respect to targeted therapy, the microrobots will deliver drugs around and referring to telemetry implies that the microrobots will sense information in different places. Such information sensing can include determining the level of oxygen or whether there exists plague at a certain location in the vessels.

Subject

The field of Robotics and AI is developing increasingly fast. Robots are becoming smaller while their computation power increases. Microrobotics has become popular due to these developments. Microbots can be used in various applications, for example, healthcare, rescue missions and surveillance.

Problem statement and Objectives

Problem Statement

Our research will focus on medical microrobots that will be used for the circulatory system inside the body. This system consists of the heart and the vessels and it is meant for carrying blood around. Since almost every part in a body can be reached by blood through the vessels, it is a very relevant topic to do research on and to innovate robotic technologies that can improve its working. Furthermore, cardiovascular diseases are globally considered as the leading cause of disability and death. That is why this report will discuss on the use of microrobots for the circulatory system. The functions that such kind of robots can fulfill are numerous, but the focus here will be placed on targeted therapy, material removal and telemetry. Targeted therapy refers to delivering drugs via the blood vessels to the required places; material removal implies that the microrobots can take care of ablation by removing plaque; performing telemetry will function as sensing and thus retrieving information from different places in the circulatory system.

Objectives

The objective to reach can be summarized by the following goal: we want to improve the adoption of the microrobots in terms of technical as well as user aspects. Accordingly, it needs to be researched what such improvement implies for the different stakeholders with respect to their needs and rights. To be able to conduct our research, we will read articles, send out surveys to the public, perform interviews with experts and simulate the design of the microrobots.

Requirements

• Controllable, the microbot should be human-controllable.
• Safe, the microbot should operate with safety as priority
• Durable, the microbot should be able to withstand the operating conditions
• Autonomy, the microbot should have some level of autonomy
• Multi-robot collaboration, the microbot should be able to communicate with other microbots and they should operate as a group

Contraints

• Size, the microbot for health should be small enough to travel in the human body.

Plan

A structured approach is needed to guide the team towards a valid answer to the research problem at hand. Therefore, the approach taken is not just limited to scientific research but also an attempt to solve a design problem.

Approach and milestones

1. Conduct research

In this objective the team conducts extensive research to find the state-of-the-art technologies in the field of medical micro-robotics. Furthermore, a summary of the research will be created to frame the most significant findings. This will allow the team to have a well-constructed Knowledge bases, which will be used in different parts of the research.

• Survey

We have made a survey to send out to the general public and another survey to send to experts (medical students and doctors). The focus in the survey for the society is on their view on technology and their acceptance in general and on the medical microrobots in this research. The survey for the experts consists of questions related to the collaboration between the robots and doctors and possible risks or medical difficulties that could arise when the microrobots get implemented.

Results Society (63 answers) The introduction of this survey is as follows: This survey is conducted to investigate the factors that affect the adoption process of this technology by the general public. We are specifically researching microrobots that will be used for retrieving information from and delivering drugs through the blood vessels in human bodies. You are free to watch the following video in order to get a better idea of the microrobots in action: https://www.youtube.com/watch?v=IviRupap7SY. The robots will not be provided with autonomy, they will follow their path according to the path planning of a computer program. The doctor is able to fill in the start and goal location in the blood vessels.

The 5 respondents that would not allow the microrobots in their body all mentioned that they would allow the robots in the future only if one of the risk factors for a cardiovascular disease becomes applicable to them. This can of course be taken into account for the implementation of the microrobots by for example making use of the ability to continuously monitor and prevent a life-threatening situation only if they are at risk due to their health condition or family history. The 5 respondents also answered ‘yes’ or ‘maybe’ on the question whether they would allow the use of microrobots to quickly dissolve the blockage in case of a life-threatening situation.

Research concordantly showed that older adults express lower levels of technology acceptance and that they more hesitantly adopt new technologies [19, 36]. However, according to the results from the survey, it has not been found that adults show a lower acceptance rate. It needs to be added here that in the survey the people were asked mainly about health technologies. It could be still possible that older adults show lower acceptance rates in other technology fields, but this is not researched by us.

38 out of the 63 people who filled in the survey are most concerned about robots operating completely autonomous without human control, with respect to the level of autonomy given to the microrobots. Out of the 63 given answers, 33 were male and 30 were female. The majority of them (55.7) does not suffer from any risk factor that contributes to the development of a cardiovascular disease. Furthermore, a majority of them (68.3%), considers the development of technology in general as the positive aspects outweighing the negative aspects.

71.4% of the people who filled in the survey, consider their level of acceptance of new health-technologies as high.

Results Experts (11 answers)

2. Design analysis

In this section the different design objects of microrobots will be defined and analyzed. This is important since it gives the team a well-rounded understanding of the design goals for both the hardware and the software.

3. Current technological Limitations

Medical microrobots that are being tested today are still subjectively primal when compared to the progress in the robotics domain. Therefore, the design, technology and engineering limitations will be investigated to define a design problem to attempt to solve.

4. Applications and autonomy level analysis

Medical microrobots have a large number of applications starting from drug delivery to surgical and all the way to DNA manipulation. Therefore, depending on the application different levels of autonomy are required and therefore, different use impacts. Therefore, a number of these applications will be carefully chosen to construct an abstract guide to the implementation of the USE analysis.

5. Experts’ views and arguments

Experts have different views on the deployment of microrobots and allowing them to be utilized to monitor and manipulate the human body. Therefore, the different pros and cons will be thoroughly analyzed in this section.

6. Impact of the technology on different stakeholders

In this section the psychological and physical impacts of this technology on different stakeholders will be addressed. This will allow the team to have a clear view on the societal impact of the technology.

7. Future possibilities and design implementation

In this section the team is given the possibility to have a creative outlook on the technology. This will allow the team to combine their imagination with objective reasoning to construct a design of a futuristic microrobot or attempt to solve one of the design problems discussed above.

Planning

Deliverables

The deliverables for this project will consist of a case study report on the technology, a USE case analysis on the impact of technology on different stakeholders, and last but not least a design/prototype of a micro-robot.

USE

User

The target group for our microrobots consists of the patients in a hospital that require certain sensing and surgery to be performed inside their human body. In general, the users can of course be classified into all civilians since it cannot be predetermined whether a person might need surgery or health care. For the users safety is of high importance since they would like the robot to do their tasks in such a way that they are safely cured or rescued. When the tasks are carried out by the robots, the patients do not have responsibility about the actions taken and are therefore not in charge of their own body anymore. This can give the feelings of inconvenience for a patient as the caring of their body is displaced by a robot.(1) Many changes have already taken place in order to improve the quality delivered by healthcare services to contribute to the safety and health of human beings in hospitals. Examples are surgery systems with partial autonomy or social robots that are used to provide aids or drugs to patients. (2)

In the case that the microrobots will work semi-autonomously, the operators will be part of the users as well. These operators are then the doctors in the hospital that may tele-operate the robots. For them it is important that the human-robot clinical settings are well designed. (3) With reference to robot technology innovations, good human-robot interaction is determined to include some aspects and an barriers should be overcome. (4) The aspects that should be present for the user interface consist of awareness, efficiency, familiarity and responsiveness. The barrier is that the sensing and perception of the robot should match with that of a human being which implies that the sensors need to be shown such that the doctor will still have sufficient situational awareness to stay capable of making a good model of the environment. (4)

Technology acceptance Research concordantly showed that older adults express lower levels of technology acceptance and that they more hesitantly adopt new technologies [19, 36]. As potential users of eHealth applications might suffer from multiple physical and psychological restraints (e.g. restricted mobility, medicament-induced side-effects, pain, dementia, cognitive deficits, etc.), an even stronger (negative) impact of individual factors on eHealth technology acceptance is expected than in healthy user groups.

Technology adoption It has been found that the primary concern was misuse of robots in the medical and healthcare fields, classified into loss of human interaction (78%) and replacing professionals and staff (36%). There were concerns about cost and health care coverage (21%), and also about education (14%).

Society

Important stakeholders for the use of the microrobots are the medical personnel, hospitals and EMA (European Medicine Agency). Furthermore, it is relevant that the society accepts the technology and thus it needs to be checked whether people are willing to let such robots to the work. Especially the level of privacy for citizens need to be guaranteed since the robots are mobile and able to gather personal data such that the government also plays an important role in the implementation of the microrobots(1). Next to that, the acceptance of robot technology in healthcare is generally considered to have a low rate due to complications in human-robot interaction. Such complications include a fear of displacement by a robot, safety and appropriateness(1).

Enterprise

First of all, to make the design of a good microrobot to be used, experts in robotics and automation are required. Due to the fact that aspects influencing the innovation of robot technology do not stay the same over time, research needs to be continued on the technologies used and new adoptions should be made where possible. Accordingly, the capabilities and functionalities of technologies will evolve and this needs to be taken into account within the company or institution that will be in charge of the robots. Furthermore, when microrobots become able to perform the required actions fully autonomously, this will influence the number of jobs that will stay available within the healthcare services. Doctors might lose their job as human tasks will be replaced by the work done by robots.

State of the Art

Microrobots in Healthcare

https://search.proquest.com/docview/2511387399/fulltextPDF/2C3A36D2DB8F4436PQ/1?accountid=27128 Healthcare Robotics: Key Factors that Impact Robot Adoption in Healthcare - Definition of microrobots: o Microrobots are defined as untethered robots of a size significantly small that are able to move around the body in order to fulfill tasks such as sensing, material removal or targeted therapy. (can be used for the introduction part of the report) The effective design of human-robot clinical settings will require partnerships between experts in robotics and automation, human-computer interaction, cognitive sciences, as well as clinicians, caregivers, and psychologists. A limitation of this study is that factors influencing robot technology adoption are expected to change over time since the functionalities and capabilities of clinical robots are expected to continuously evolve. In this changing environment, standards and legal implications established by regulatory bodies will also need to evolve. (3)

Autonomy

According to (Attanasio et al., 2021) robots can have six different levels of autonomy Level 0: No autonomy; the robot is fully controlled by the operator. Level 1: Robot assistance; the robot is capable of interacting. It’s function is to guide or support it can provide active or passive assistance. It has tasks like: tool tracking, eye tracking and tissue interaction sensing. Level 2: Task autonomy; the robot can do certain tasks on its own, the control switches between the robot and the operator. Level 3: Conditional autonomy; the robot has the ability of perception, planning and updating plans during execution. The control still switches between operator and robot. It executes tasks like modeling, imaging and navigation. Level 4: High autonomy; the robot has the ability to interpret information, do interventional planning and execute this autonomously. The operator is there to supervise. Level 5: Full autonomy; The robot can fully operate on its own without influence of the operator Attanasio et al. states that when reaching level three or higher different problems can arise such as accountability, liability and culpability. These kinds of problems arise when for example decision errors are being made. According to Sitti et al. the levels of autonomy can also be divided into on-board and off- board approaches. On- board is untethered, self- contained and self-propelled and thus has ‘has all on-board components to operate autonomously or with a remote control’ (Sitti et al., 2015). While off-board approach is senses, powered and controlled from the outside

Ethical Aspects

https://onlinelibrary.wiley.com/doi/epdf/10.1002/rcs.1968 Legal, Regulatory and Ethical Frameworks for Development of Standards in AI and Autonomous Robotic Surgery This article discusses the regulation, legal and ethics aspects that come forward in using medical robots or other kinds of robots that include a certain level of autonomy. In general, it is stated that current issues with robotics for medical use are similar to those of robotics engineering problems. With respect to autonomy, it is determined that if no autonomy at all is present for the robot, the number of ethical issues would decrease. However, it is important that doctors take part in training that will focus on how they should use the technology and thus participation is crucial.

Safety

https://onlinelibrary.wiley.com/doi/full/10.1002/advs.202002203 The development of biorobots has the potential to create fully autonomous micro/nanorobots in the interface of growth and assembly. Moreover, integrating biomaterials into the robot design could increase its safety and cloak it from a patient immune system. To pass such regulatory hurdles, new technologies need to demonstrate their safety and efficacy.[410, 411] The probability of getting approval is historically very low and is also very costly and time‐consuming. Artificial intelligence and machine learning could also help to increase the safety of micro/nanorobots. Local path planning algorithms could help train micro/nanorobots to navigate in the unknown and dynamically changing biological environments, thus avoiding hitting obstacles and getting stuck inside the body.[413]

Human-Robot Collaboration

https://dl.acm.org/doi/pdf/10.1145/1121241.1121285 (4) Effective User Interface Design for Robotics This article talks about human-robot collaboration including some barriers that come along with it and attributes that contribute to a good working collaboration. First of all, it is stated that an operator using the robot should place themselves in a position similar to that of the robot. Two barriers will then arise in such a situation: The first barrier is about the fact that the robot has a different morphology to the person that is operating it (human) This implies that there should come a suitable mapping between what the user sees as intuitive movements which should be changed into sensible movements in the robot The second barrier include the perception and sensing part since the user and robot are not in the same position and the robot’s sensors might mismatch with the sensors that human beings know how to use Consequently, sensors that are familiar, needs to be shown such that the user can receive situational awareness that will make him or her capable of creating a good mental model with respect to the environment The attributes that will make human-robot collaboration better are not yet there, but there are a few well established recommendations on creating a good human-robot interface Such recommendations consist of ensuring that the interfaces for human-robot interaction should have a clear starting point and they should be conceptually as well as visually comprehensible. Also, the design should be pleasing and congruent with the actions at hand and the human being involved in the interaction: Awareness > there should be sufficient information for the operator such that he or she can make a complete model of the internal and external state of the computer Efficiency > there should not be too much movement possible that is needed in the hands and focus of attention Familiarity > concepts to which the user is not used to need to be avoided or minimized Responsiveness > include feedback from the robot to the user about either the failure or success of certain tasks that are performed https://www.researchgate.net/profile/Iroju-Olaronke/publication/316717436_State_Of_The_Art_A_Study_of_Human-Robot_Interaction_in_Healthcare/links/590f3b6eaca2722d18604958/State-Of-The-Art-A-Study-of-Human-Robot-Interaction-in-Healthcare.pdf A Study of Human-Robot Interaction in Healthcare - Human-robot interaction in healthcare is faced with challenges such as the fear of displacement of caregivers by robots, safety, usefulness, acceptability as well as appropriateness > lead to a low rate of acceptance of the robotic technology - One of the major challenges confronting human-robot interaction is the loss of privacy as social robots are mobile, they act as social actors and they also have the ability to gather data - The robot can act autonomously or be teleoperated in an environment which means that it the robot is fully controlled by a human being

Currently existing prototypes

https://wecanfigurethisout.org/NANO/lecture_notes/Nano_challenges_and_fears_Supporting_materials_files/Nano%20Medicine/Journey%20to%20the%20Center%20of%20a%20Tumor%20-%20IEEE%20Spectrum_Oct_2012.pdf Minibots for Medical Missions Magnets are used to steer the microrobot through blood vessels. This implies that with the use of magnetic nanoparticles, microrobots are expected to move very fast through vessels in order to perform actions like drug delivery or removal of plaque in arteries. There are several prototypes proposed in this article with different medical goals. The system that is discussed in particular is the MRI machine which consists of a magnet that generates a magnetic field which is significantly stronger than the field of the earth. There are radio-frequency waves that are transmitted and the signals retrieved from the process around it will provide information such that bones from blood can be distinguished and tumors from the ‘healthy stuff’ in the body. Another prototype is that of ‘plaque busters’ which can be used to do the material removal part as it can remove the plaque that is present in arteries. Furthermore, the ‘magnetic microcarriers’ and ‘bacteriabots’ can perform drug delivery while ‘corkscrew swimmers’ can act as vessel navigation.

Movement

Currently existing prototypes can move through the bodies in different ways such as helical and chemical propulsion, traveling wave propulsion, pulling with magnetic field gradients and clinical magnetic resonance imaging systems. To access vessels smaller than arterioles SItti et al. proposes a technique inspired by flagella swimming bacteria, they are rotating magnetic microswimmers with a helical tail. According to … microrobots with an elastic tail has several advantages compared to a rigid body microbot. The one with the elastic tail can for example move wireless and more freely than the rigid body it also performs better regarding speed and energy efficiency. Tasks Nelson et al. States that microrobots inside the body can perform different types of tasks such as targeted therapy, material removal (ablation and biopsy), controllable structures (stent, temporary implant, scaffold or occlusion) and telemetry (transmitting location or concentrations). Drug delivery Sitti et al. propose some techniques to trigger the drug release mechanism at the correct moment. This can be achieved by near-infrared light, ultrasound, visible light and magnetic fields.

Constraints of Microrobots

An important aspect regarding robots that enter the body is that tissues cannot be damaged and the body should not fight against the bot so the material needs to be body friendly. Besides they need to operate flawless in a dynamic, ever changing environment which is the body. Drug delivery Challenges regarding drug delivery are dosing, selective release and biodegradation- retrieval.

Microrobots in Healthcare

Combination of 4 articles (Tumbling Microrobots for Future Medicine, Translational prospects of untethered medical microrobots, Medical microrobots have potential in surgery, therapy, imaging and diagnostics, magnetically powered microrobots: a medical revolution on the way)

Microrobots will replace surgery and even bottles of medication by simply being injected in the body. Microrobots are: A microscopic-scale automated machines designed to perform selected movements in response to specific stimuli. Different Functions: 1. They might clean out arteries that are blocked with plaque 2. Perform highly targeted tissue biopsies 3. Treat cancerous tumors from the inside Advantages: 1. Far less likely to cause tissue damage than conventional medical interventions such as surgical incisions and catheter insertions. 2. Reduce side effects of pharmaceuticals by aiming for a specified destination in the body 3. Could enable tissue engineering and regenerative medicine, where damaged tissue and organs could be repaired or entirely rebuilt. Currently existing prototypes The advancement in semiconductor techniques created a surge in microscale medical microrobots. They are a natural extension of the microelectromechanical system (MEMS) devices. Main Problem that affects this technology: 1. Fabrication (How can we get them to be smaller) 2. Locomotion and Control (the system can’t get stuck in the body) 3. Visualization technologies 4. Complex end effectors for environment manipulation However, for drug delivery these problems are relatively straightforward. Where a Micro robotic system simply triggers a payload-release mechanism after being guided to a target location in the body. An Example of this; is the autonomous microrobot that is propelled by hydrogen microbubbles have been used in live mice to treat gastric bacterial infection. Comparison between traditional drug delivery and micro robotic drug delivery: Traditional: rely on passive diffusion to reach a desired area Microrobots: guided to a much closer location to the target This precision delivery means that a higher concentration of the drug will arrive at the most beneficial area and therefore the risk of side effects is minimized. Examples of current active robots: Approaches for mobile micro robotic actuation: · Acoustic actuation: microrobots move toward sound generated pressure points driven by oscillating sound waves that are applied to the fluid surrounding them. · Chemical actuation: methods include propulsive chemical motors that expel microbubbles or use local chemical gradients to generate thrust forces. 2. Biohybrid designs: that take advantage of self-contained energy and mobility of living cells · Approach: coupling bacteria, sperm, or muscle cells to artificial structures and controlling them remotely by varying the surrounding temperature, acidity, lighting conditions or magnetic fields. · Optical actuation: can generate crawling locomotion on elastomer materials, which contract when directly heated by lasers. The problem with many of these methods is that they can be used only in controlled environments. Therefore, the most popular form of actuation is magnetism, which is well suited for the use in vivo · Magnetism actuation: By embedding magnetic material inside or around its form, we can manipulate a microrobot with external magnetic fields. (How these two field parameters vary over time, in addition to the field’s magnetic strength, determine exactly how the microrobot moves) · Microswimmer robot designs are appealing for in-vivo applications due to their ability to maneuver three dimensionally in fluid environments. Typically, the motion of the flagella is driven by rotating magnetic fields, although some research groups have demonstrated thermal-driven versions. The Tumbling solution: Rolling or tumbling microrobot using magnetic torque is more effective than pulling it along a magnetic gradient. Much as a rotating magnetic field can be applied to spin artificial flagella, it can be used to rotate blocklike surface tumblers Instead of fighting against friction, the μTUMs use it to their advantage to grip the surface and move forward. They can tumble off ledges and into valleys several times their size and use adhesion to climb steep inclines. They can also move through liquids and tumble across many different surface textures. Furthermore, magnetic torque propulsion from tumbling is more energy efficient than magnet force propulsion. This energy efficiency is crucial since you don’t want the human body to heat up from the high-power magnetic field and suffer damage. Further research is looking into creating a swarm group of robots that can communicate and work together.

Constraints

Micro vs Macro scale robots: Micro robots have severe constraints that generate from their small size. Therefore, the contemporary Knowledge that we have in macroscale robots cannot be directly transferred to microscale. The most significant constraints: 1. Can’t incorporate onboard: · Power source · Sensors · Computer circuitry 2. Some features can’t be there such as: · Motors · Electronic sensors · Self-contained intelligence 3. Use of materials: · Biodegradability and biocompatibility are crucial aspects to avoid immunogenic reactions 4. Small size operating restrictions: · Volumetric effects (such as weight and inertia) become insignificant compared to surface area effects (such as electrostatic attraction, adhesion and drag). explains restriction to mobility. · Visualization technology harder to incorporate

https://pubmed.ncbi.nlm.nih.gov/20415589/

Potential impact of medical microrobots

Functions for microbots:

Targeted therapy Targeted drug delivery (reduces risks of side effects in other parts of the body) Brachytherapy is the placement of radioactive source or seed near a tumor Hyperthermia and thermoblation is the local delivery of heat energy to destroy cells Material removal Ablation Biopsy Controllable structures Microbot can be used as scaffold or provide building blocks (restructuring) Stent Occlusion Permanent or temporary implant Telemetry (transmitting information) Remote sensing transimit time history of for example oxygen concentration Marking and ransmitting position to outside world (to localize internal bleeding) Application areas for microbots

Circulatory system (heart and vessels) Central nervous system Urinary system and prostate The eye The ear The fetus Different kinds of movement

Helical propulsion Traveling- wave propulsion Pulling with magnetic field gradients Clinical magnetic resonance imaging system Conclusion

Minimally invasive techniques reduce postoperative pain, hospitalization duration, patient recovery time, infection risks, and overall cost, increasing the quality of care. Their design will be based on the task they need to accomplish and the type of environment in which they will operate. Developing this technology requires that we address issues such as localization and power, always keeping in mind that microrobots will be utilized in vivo.

Design

Navigation

Control

The navigation method adopted in this report will mainly focus on the magnetic actuation by alternating magnetic field. This method was adopted due to its relative simplicity compared to other methods of actuation such as acoustic or chemical. However, there is a certain limit to the power of the magnetic field applied and the duration, since the human body can only absorb so much of it before it starts to heat up. Therefore, the magnetic actuation must be as efficient as possible by trying to minimize the unwanted surface area effects.

Pathfinding

To let the microbot reach the goal as efficiently as possible a pathfinding algorithm should be used if the goal is already known. The field of pathfinding is already heavily studied and there are a few pathfinding algorithms that can be used. Dijkstra’s algorithm is an easy algorithm to implement. At each step the cost of the next step is computed and the smallest cost path is than chosen. A* is the most used pathfinding algorithm, because it uses a heuristic combined with Dijkstra’s algorithm to plan. The heuristic gives a value for the cost towards the goal and makes sure only the optimal paths are considered and the other paths don’t get computed.

Operator involvement and autonomy WIP

The level of autonomy of this technology until now is very minimal, this is due to the Computational limitation discussed in section /ref{} . However, technological advancements are very rapid and could cause a significant impact on such systems. It is simply required to reach a certain size of digital circuitry to allow these systems to contain onboard intelligence. Unfortunately, phenomena, such as voltage arc jumps and electron quantum phenomena are making the problem more complex. In other words, moore’s law is soon reaching its limit.

Furthermore, three discrete levels of autonomy will be addressed in this section. Firstly, the present level, which is low autonomy, where the robot is simply controlled by the doctor. Secondly, the close future, which is a medium external level of autonomy, the robot is controlled using an external algorithm. Finally, in a distant future approach, which is a high level of on-board autonomy, the robotic system becomes completely autonomous.

Survey

We have made a survey to send out to the general public and another survey to send to experts (medical students and doctors). The focus in the survey for the society is on their view on technology and their acceptance in general and on the medical microrobots in this research. The survey for the experts consists of questions related to the collaboration between the robots and doctors and possible risks or medical difficulties that could arise when the microrobots get implemented.

Results Society

The 5 respondents that would not allow the microrobots in their body all mentioned that they would allow the robots in the future only if one of the risk factors for a cardiovascular disease becomes applicable to them. This can of course be taken into account for the implementation of the microrobots by for example making use of the ability to continuously monitor and prevent a life-threatening situation only if they are at risk due to their health condition or family history. The 5 respondents also answered ‘yes’ or ‘maybe’ on the question whether they would allow the use of microrobots to quickly dissolve the blockage in case of a life-threatening situation.

Research concordantly showed that older adults express lower levels of technology acceptance and that they more hesitantly adopt new technologies [19, 36]. However, according to the results from the survey, it has not been found that adults show a lower acceptance rate. It needs to be added here that in the survey the people were asked mainly about health technologies. It could be still possible that older adults show lower acceptance rates in other technology fields, but this is not researched by us.

38 out of the 63 people who filled in the survey are most concerned about robots operating completely autonomous without human control, with respect to the level of autonomy given to the microrobots. Out of the 63 given answers, 33 were male and 30 were female. The majority of them (55.7) does not suffer from any risk factor that contributes to the development of a cardiovascular disease. Furthermore, a majority of them (68.3%), considers the development of technology in general as the positive aspects outweighing the negative aspects.

71.4% of the people who filled in the survey, consider their level of acceptance of new health-technologies as high.

Limitations of Microrobotic Systems

The current technology of microrobots for the medical field is extremely limited due to the hostility and diversity of the environment in which they operate. For one to define the limitations of such a system one has to first understand the physics behind going to the micro or nano scale. Another point is to define the different design parameters and the current state of the art technologies that could be used to overcome such shortcomings.

Firstly, the physical limitations when going to the micro scale. These limitations occur due to the very small body size of the robot. Such effects are seen in the behavior of insects with their environment, where some of them can walk on water others can fall from great heights without damage. These phenomena occur due to the relation between the volumetric and surface area effects. The volumetric effects are for example inertia and mass, while the surface area effects are drag, electrostatic attraction and adhesion. Therefore, due to the robots small size these volumetric effects are negligible compared to surface effects. This causes major issues for navigation and control of the robot, since the robot could get stuck in places where it shouldn’t be and that’s a major risk for the patient's health.

Secondly, the material used for these systems must be very specifically chosen, as this system has to be safe to roam around in the body. Therefore, the level of toxicity and the method of extraction of such a system must be addressed as design parameters. The main limitation here is tissue, as the body is designed to reject foreign bodies. Therefore, the robot can’t stay in the body for a long period of time and a method of extraction must be addressed. Some solutions were proposed, such as, the use of biodegradable materials that when the robot finishes its task it could basically dissolve in the body without intoxicating the cells around it. Another material limitation is dependent on the method of navigation of the robot. In an attempt to illustrate this, for magnetic actuation the microrobot must be made of magnetic material to be able to respond to the alternating magnetic field. For these reasons, the choice of the material is very limited.

Thirdly, Computational and electronic limitations. These limitations are due to the small size of the robots and the current computational technology, as these robots can’t have sensors or complex digital circuits like the macro scaled robots. For similar reasons, these micro systems still can’t have on-board intelligence. Therefore, the transition from robotic knowledge in the macro scale cannot be directly applied in the micro scale. However, with the advancement of technology and Moore's law it suggests that it won’t take long for computational circuits to get that small.

Furthermore, this computational limitation causes a major drop in two different design parameters, navigation and visualization. The navigation issue surfaces from the fact that no motors or actuators could be applied. On the other hand, for visualization all the sensing components, such as, camera’s, LIDAR, radar, etc. can't be applied as well. Therefore, the whole process of navigation and visualization is controlled externally, such as magnetic actuation and CT scans, respectively.

Therefore, the design parameters differ drastically depending on the functionality of the microrobot. For instance, a robot that is meant to drop a medicine has completely different design parameters than a robot meant for conducting eye surgery. Moreover, the design parameters are most generally defined to be Navigation and control, environment manipulation and accutation, visualization and sensing. Then the designing process is then initialized by defining the purpose of the microrobot, the media that it's going to operate and the level of autonomy.