Seminar On Mems In Medecine

2008

Seminar on MEMS in Medicine

Department of Mechanical Engineering SDM-CET, Dharwad

Chetan Purushottam Bhat B.E (Mechanical)

Bio-MEMS

Synopsis In the past few decades, microelectromechanical systems (MEMS) have found themselves being adopted into a wide variety of fields and disciplines. Recently there has been an increased interest in the use of MEMS in medicine, with opportunities in areas such as surgical Microsystems (intelligent micro invasive surgery), Therapeutic Microsystems (health care management system), and Diagnostic Microsystems (biochips and related instrumentation). The key to many of these applications lies in the leveraging of features unique to MEMS. BioMEMS represents a promising new direction in meeting 2lst century health care challenges. Opportunities in miniaturization allow for new medical procedures to be performed as well as existing procedures to be carried out less invasively. The ability to apply batch fabrication methods to the manufacture of BioMEMS might also enable greater accessibility to medical procedures through a lower overall cost of health care delivery. BioMEMS is expected to revolutionize the way medicine is practiced and delivered.

Picture of a 350 micron high microneedle, with a base of 250 microns, the flow channel is 70 microns in its widest direction.

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

OBJECTIVES

• To study the different types of sensors used in BioMEMS devices. • To understand the working principle of BioMEMS devices. • To study the considerations for product development of BioMEMS device. • To study the design and fabrication process of BioMEMS device. • To study the different applications of BioMEMS devices in Medicine.

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

INTRODUCTION WHAT IS BioMEMS? Microelectromechanical systems (MEMS) are devices that have a characteristic length of less than 1 mm but more than 1µm. MEMS refer to a collection of micro sensors and actuators that can sense its environment and have the ability to react to changes in that environment with the use of a microcircuit control. They include gyroscopes, motors, pumps in addition to the conventional microelectronics packaging into microelectromechanical structures for desired sensing and actuating functions, on a silicon substrate that can be smaller than a grain of sand. The system may also need micropower supply, microrelay, and microsignal processing units. Microcomponents make the system faster, more reliable, cheaper, and capable of incorporating more complex functions. For example, the blood pressure sensors that used to cost $600 and $50 for every use now costs $2. Biomedical Microelectromechanical systems (BioMEMS) integrate microscale sensors, actuators, microfluidics, micro-optics, and structural elements with computation, communications, and controls for application to medicine for the improvement of human health. In general, BioMEMS can be defined as ‘‘devices or systems, constructed using techniques inspired from micro-scale fabrication, that are used for processing, delivery, manipulation, analysis, or construction of biological and chemical entities’’. These devices and systems encompass all interfaces of the life sciences and biomedical disciplines with micro systems. [1]

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

ADVANTAGES Lower cost Owing to the batch-mode manufacturing techniques borrowed from the integrated circuit industry, small size die, and consequently large volumes and lower cost have become possible. [2] Reliability Silicon is an almost perfectly elastic material. It also doesn’t erode (wear out). Micromachines last much longer than their macro counterparts. Higher performance Arrayed sensors can provide simultaneous sensing of multiple modalities (pressure, temperature, chemical reactions ... etc.), or for increased dynamic range, or for microscopic scale spatial discrimination of signals [2] Real-time feedback MEMS technology provides the real-time feedback surgeons that can improve surgical outcomes, lower risk, and help control costs by providing the surgeon with real-time data about instrument force, performance, tissue density, temperature, or chemistry, as well as provide better and faster methods of tissue/fluid preparation, cutting, and extraction. [4] Versatility The devices can be activated in several different ways. It can be activated by remote control, giving control to the doctor or the patient. It can be activated on a set time basis. Some devices are even automatically triggered by sensors built into the device that detect when the drug needs to be administered. [3] Minimal Invasive Surgery Leads to shorter hospital stay and faster recovery times for the patient. The cost of a minimally invasive procedure is 35% lesser compared to its open surgery counterpart. While MIS has many advantages to the patient, such as reduced postoperative pain, shorter hospital stays, quicker recoveries, less scarring, and better cosmetic results. [4] Tissue Sensing The ability to distinguish between different types of tissue in the body is of vital importance to a surgeon. For example, if a neurosurgeon cuts into a blood vessel while extracting a tumor, severe brain damage may occur.

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

Lab-on-a-chip systems The advantages of such systems are the microvolumes of biological or biomedical samples that can be delivered and processed for testing and analysis in an integrated fashion, therefore dramatically reducing the required human involvement in many steps of sample handling and processing, and improving data quality and quantitative capabilities. This format also helps to reduce the overall cost and time of the measurement and at the same time improves the sensitivity and specificity of the analysis.

DISADVANTAGES [5] 1) Fabrication facilities are too expensive to be installed only for small volume production. (2) Because MEMS fabrication process differs from a device to another, a designer should know many variations of processes; such high-level designers are very few. (3) The optimization of a MEMS device requires many repetition of design modification and trial fabrication. This makes the development phase long and costly. (4) Those who want to utilize MEMS in various products may not have enough knowledge of MEMS technology; thus they cannot take the full advantages of the technology.

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

CHOOSING SENSORS FOR MEDICAL APPLICATIONS [6] There is a need to reduce manual labor and human error as well as to increase reliability and process automation. The kind of intelligence needed to achieve these objectives can be provided with sensors. Sensors are used in equipment for surgical procedures, intensive care units, hospital recuperative care, and home care. With medical equipment manufacturers and sensor experts working together, state-of-the-art technologies can be created. Selecting a sensor can be simple if the application and the parameters that need to be controlled are clearly understood.

Implantable Sensors Implantable sensors need to be small, lightweight and compatible with body mass as well as require very little power. Most importantly, they cannot decay over time. The power requirement is one of the major challenges for working with implantable sensors. Sensors that can function with no power are perfect, but there are few in the market. Piezoelectric polymer sensors are small, reliable, require no power and last for a long time. Such sensors (miniature Piezo film sensor) can be used in pacemakers that monitor activities of the patient. There are other ways to power implanted sensors from external sources. When an RF energy wand is brought close to the location of a specially designed sensor located inside the body, the sensor wakes up, takes measurements, sends the data back to the wand by RF link, and goes back to sleep. A sensor with an antenna and a transpondent will do this job. As an example, an abdominal aortic aneurysm requires a portion of the weak arteries to be removed and replaced with synthetic tubes. Such a sensor can be implanted during the procedure to monitor the pressure leaks at the surgical location.

Miniature Piezo film sensor enlarged about 10x

Pacemaker X-ray

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

Temporary Inserted Sensors The requirements for sensors that can be inserted through an incision— typically through a catheter—are less critical than those for implantable. Depending on the surgical procedure, they need to function for few minutes to a couple of hours. Ideally, these sensors do not require power to operate, but, if necessary, they can be powered by external means. A pair of matched thermistors can be attached to the tip of a catheter, which can be guided to different locations of the heart to measure blood flow. These thermistors don’t require external power. The figure shows this type of sensor. Catheter ablation sensors are another example of sensors temporarily inserted through incision to effect specific treatments and/or to take measurements during treatment. It is critical that the force applied by the catheter tip to the target tissue not exceed predetermined values to avoid any possibility of perforating the target tissue.

Temporary temperature sensor catheter probe

External Sensors Exposed to Fluids There are several disposable sensors where the sensor stays outside the body, but body fluids come in contact with it. One example is disposable blood pressure sensors (DPS). These sensors are used in surgical procedures and ICU to continuously monitor the blood pressure of the patient. This is the ideal way to measure blood pressure when intravenous fluids (IV) are administered to the patient. These sensors are replaced once every 24 hours to maintain hygiene. This sensor module is plugged in to a monitor to log all information. A few other sensors come in contact with medication and/or body fluids. One is the sensor used in the inflation of an angioplasty balloon. In this application, the pressure

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

sensor needs to withstand more than 30 bars and monitor the pressure applied to inflate the balloon. Too much pressure can burst the balloon. Since medication and body fluids are coming in contact, a silicone gel barrier is used to isolate the rest of the sensor.

Disposable blood pressure sensor

Devices and External Applications Medical devices use sensors for external applications in which neither medication nor body fluids come in contact with the sensors. In most cases, these are non-disposables. They can either be used in hospital or home care applications. Examples include: • Load cells for infusion pumps that detect occlusion (tube blockage) • MEMS-based flow sensors used in spirometers to measure breathing strength of asthmatic patients • Extremely small MEMS-based accelerometers to study tremors in Parkinson patient • MEMS and load cell-based sensors for the conservation of oxygen and also to monitor oxygen tank levels • NTC temperature sensors to measure skin/body temperature

Infusion pump load cell to detect occlusion Reusable NTC thermistors used to measure skin or body temperature

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

Working Principle of BioMEMS device The applications of BioMEMS can be classified into • Diagnostic • Therapeutic • Surgical

Diagnostic system [7] The objective of diagnostic system is to discover what is wrong with the people who are ill. The rapid developments in the field of biochemical sciences, immunology, molecular biology and semiconductor microfabrication technology has led to the concept of microdiagnostic kits. The principle of the microcantilever based diagnostic kit for tuberculosis is similar to that of the diving board as the increase in the adsorbed mass of antigen 85 complex causes the bending of the microcantilevers. But in addition to that, the specificity is provided by the immobilization of antibodies specific for antigen 85 complex on the upper surface of the microcantilever. When the biomolecular recognition takes place between them, the adsorbed mass of antigen 85 complex causes the change in stress on the surface of the microcantilever. The difference in stress at the top and the bottom of the microcantilever beam causes the elongation of the upper surface of the microcantilever and the shortening of its lower surface thereby causing the nanomechanical bending of the microcantilever. The deflection of the cantilever can be detected by optical, capacitive, interferometric or piezoresistive method.

Microcantilever Based Microdiagnostic Kit For Tuberculosis

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

The microcantilever based microdiagnostic kit for tuberculosis would be composed of a reference and a sensing microcantilever. The mechanical properties of the reference microcantilever are exactly similar to that of the sensing microcantilever as they have the same coatings of immobilized biomoleules, same composition and same dimensions. The use of reference microcantilever is very important as it eliminates nonspecific interactions, thermal drifts and turbulences from injections of liquids. The device would have two inlets for the patient sample and the normal sample. The patient and the normal sample would be delivered to the respective sensing and reference microcantilevers in the device. The unused sample and reagents would be ejected out of the device through the outlets directly below the microcantilevers. The biochemical interactions between the antigen 85 complex and the immobilized antibodies would cause the change in resistance of the piezoresistor integrated at the anchor point of the sensing microcantilevers with respect to their reference microcantilevers. Based on the reading of the display reader, the relative resistance change would be recorded. This would provide information regarding the disease state of the patient sample enabling effective diagnosis of the disease and early treatment

Therapeutic System The objective of therapeutic system is to treat an illness or improve a person’s health. Therapeutic microsystems offer the potential of autonomous care management and precision delivery of medications. Some key MEMS technologies currently being incorporated into such systems include micropumps, microvalves, and microneedles. Biomedical microdevices can benefit many patients with neural disorders. Among the most successful examples are cochlear implants for the hearing impaired, cardiac defibrillators, and deep-brain stimulators for the treatment of Parkinson disease and other movement disorders. Implantable and transdermal drug delivery microsystems allow patients both accurate and continuous dosing of medication and allow delivery of drugs directly to their intended sites of action. [8] Ocular drug delivery device [9] utilizes a passive delivery mechanism to eliminate the need for control electronics and thus reducing the cost of the system. In order for the device to be a viable treatment method for chronic diseases, it must be refillable to allow repeated dosing for many years. Once implanted, the device must precisely and repeatedly deliver accurate doses and hold enough medication for multiple doses prior to refilling (~every 2 months). The device should be flexible and conform to the natural curvature of the eye. An ocular drug delivery device and its placement relative to the eye are illustrated in figure below.

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

Concept of a refillable ocular drug delivery device

The drug delivery tube diameter is set to less than 1 mm. For incisions of this size, the eye is able to maintain its integrity without the aid of sutures. Support posts are contained within the tube and the reservoir to prevent the top surfaces of the device from collapsing when the drug is depleted. A normally-closed check valve prevents backflow of fluids from the eye into the device. The valve opens above a certain cracking pressure allowing drug to be dosed from the reservoir to the treatment site. The intraocular drug delivery device is composed of three individual structural layers of polymethyldisiloxane (PDMS). The top layer defines the chamber for the refillable drug reservoir. The middle layer defines the delivery tube and check valve orifice. The bottom layer forms the base of the device outlining the refillable chamber, delivery tube, suture tabs, and check valve seat. This layer contains posts that serve as (1) mechanical supports to prevent the tube or reservoir from collapsing and (2) the valve seat for the check valve. The reservoir is secured to the top of the eye, while the shunt is inserted into either the anterior or posterior chamber (Figure a). A specific dose of medication is dispensed from the device when the reservoir is manually depressed by the patient’s finger (Figure b). The reservoir can be refilled with the same or different medication without additional surgery (Figure c).

Illustration of device operation

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

Surgical system [4] Surgery is the treatment of diseases or other ailments through manual and instrumental means. New technologies and procedures have been focusing on minimizing the invasiveness of surgical procedures. Advances in surgery have led to greatly reducing or eliminating the invasiveness of surgical procedures. Current robotic surgery systems have a number of benefits over conventional surgery. Figure (a) shows an Intuitive Surgical Da Vinci robotic system. In this arrangement, the surgeon sits comfortably at a computer console instead of having to stand throughout the entire procedure, which can last up to 5 h. A three-armed robot takes his place over the patient. One arm holds an endoscope while the other two hold a variety of surgical instruments. The surgical team can also look at a video monitor to see what the surgeon is seeing. The surgeon looks into a stereo display and manipulates joystick actuators located below the display. This simulates the natural hand-eye alignment he is used to in open surgery (Figure b). Since computers are used to control the robot and are already in the operating room, they can be used to give the surgeon superhuman-like abilities. Accuracy is improved by employing tremor cancellation algorithms to filter the surgeon’s hand movements. This type of system can eliminate or reduce the inherent jitter in a surgeon’s hands for operations where very fine precise control is needed. Motion scaling also improves accuracy by translating large, natural movements into extremely precise micromovements. These advances allow surgeons to perform more complex procedures such as reconstructive cardiac operations like coronary bypass and mitral valve repair.

Intuitive Surgical Da Vinci robotic system

Intuitive surgical stereo display and joysticks.

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

PRODUCT DEVELOPMENT When developing a MEMS-based product for the surgical market, it is important to keep the end in mind. The greatest whiz-bang sensor design and fabrication technology will not produce a marketable product if the right application is not chosen. The following points should be taken care of while developing a BioMEMS device.

Evaluate the market [4] As when building any MEMS product, it is important to evaluate the market for the device, and in this regard the surgical market is a good one. Targeting a disease for which there are a large number of surgical procedures performed, such as heart, lung, cancer, etc., will ensure that the device will receive the required attention from funding sources, researchers, and surgeons. For example, coronary artery disease has a 120billion-dollar economic impact, which has fueled research and development of catheter devices. The surgical device market has both low-volume/high value products and highvolume/low-cost devices. The high-volume market is very price sensitive and has low margins but high volumes, which are attractive to MEMS fabrication facilities.

Interfacing early with the medical community [4] While it is always important to know your target audience, this is especially important when developing surgical tools. Partnering with surgeons and doctors early in the design process yields a deeper understanding of the problems and issues faced in the operating room. This can shorten the development cycle, as well as result in a tool which better matches the surgeon’s needs. These surgeons and doctors will be the end users and clinical champions of the surgical devices and can not only help MEMS engineers to understand what the real problem to be solved is, but also ensure that the device is accepted in the medical community. Interfacing early with the medical community will help to determine if the surgical tool is really needed and if it will be used by surgeons.

Cost [4] MEMS engineers should take an honest look to determine if MEMS really is the best choice to solve the problem, or if competing technologies will perform better. Not only must the surgical tool compete with other devices technically, but it must also compete on a cost basis. This has become more important now that medical providers are under great pressure to reduce costs. Before developing a product it is important to do the math. The device must make a significant impact on a medical procedure to justify any additional cost. In order to do this, MEMS engineers need to focus on disruptive

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

technologies which will reduce the skill needed to perform complex procedures and allow them to be performed in more convenient and lower cost settings.

Biocompatibility [10] MEMS devices which come into contact with the body must be biocompatible. Biocompatibility is defined by The Williams Dictionary of Biomaterials as “the ability of a material to perform with an appropriate host response in a specific application”. The biocompatibility requirements vary considerably depending on the device function and design; The ISO 10 993 standards outline minimum tests of material characterization, toxicity, and biodegradation that may be augmented depending on actual device usage. Biocompatibility is a surface-mediated property, and the biocompatibility of a device depends only on those materials in contact with tissue. The biocompatibility of silicon and other MEMS materials has become much more important with the advent of implantable MEMS devices that interact directly with the body. Biocompatibility is a surface-mediated property, and the biocompatibility of a device depends only on those materials in contact with tissue. The biocompatibility of silicon and other MEMS materials has become much more important with the advent of implantable MEMS devices that interact directly with the body.

Packaging [5] Packaged MEMS devices must be able to survive the sterilization procedures used in the surgical environment. They must withstand exposure to high temperatures and moisture in autoclaves and steam sterilizers. Alternative sterilization methods include ethylene oxide and irradiation. Ethylene oxide is a harsh organic solvent and packages must be made of a compatible material. For each application area the packaging challenge is different. In addition, packaging costs are usually considerably more expensive than the MEMS device itself.

Regulatory controls [4] Medical products, of which surgical tools are a subset, are subject to many regulatory controls. The Food and Drug Administration (FDA) and European Community (EC) determine whether a product is fit for sale in the United States and Europe, respectively. Any MEMS devices which have biomedical applications (BioMEMS) such as DNA chips, pumps, blood glucose detectors, catheters, cochlear implants, and blood analyzers fall under their jurisdiction. Historically BioMEMS have had design cycles between 5 and 15 years long. Of this time, one to two years have been used for getting

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

the necessary agency approvals. Agencies require that all claims be verified for effectiveness and that the product has proven to be reliable in many sets of clinical trials before they allow a product on the open market. The approval process for disruptive technology can be substantially longer. These agencies also have current good manufacturing practices (cGMP) on how medical devices must be fabricated. These procedures establish a set of standards which aim to ensure that quality products are produced. Lengthy sets of clinical trials can be avoided if MEMS sensors are applied to existing surgical tools and do not claim to alter the performance. Retrofitting existing surgical tools is the preferred method of entry for MEMS companies because it is the fastest path to market. Retrofitted tools have already been accepted by surgeons who are familiar with their applications and use. Another advantage for MEMS companies is that they themselves do not have to pay for costly clinical trials, which can be avoided by modifying existing tools. If clinical trial cannot be avoided, MEMS companies can partner with device manufacturers to reduce costs and use their expertise in trials.

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

Design and Fabrication of BioMEMS devices The design process of BioMEMS device is similar to the IC design. The parameters considered for BioMEMS design are as below Conception of new device CAD design and simulation Fabrication

Concept of new device [11] Once a study is carried out as to the requirements of the surgeon or doctor a BioMEMS engineer has to decide on the size, material, precision and accuracy, sensing element, actuation element, type of link etc. In case of BioMEMS the selection of the material is of utmost importance. Depending on the application of device either external or internal, suitable material has to be selected. The material must not be degradable or corrodible when it comes in contact with body fluids. CAD Design and Simulation [11] A Particular challenge for MEMS is the establishment of self-contained, completer and integrated modeling and simulation suite appropriate to computational analysis requirements. The Finite Element Analysis software has proven useful for modeling a variety of parameters like displacement stress, electric field, magnetic field, temperature and fluid velocity. Using the MEMS-specific tools complete structural and operational analysis can be done.

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

The software’s available for MEMS design are MEMCAD and CAEMEMS

Fabrication Techniques Bulk Micromachining Bulk micromachining is a fabrication technique which builds mechanical elements by starting with a silicon wafer, and then etching away unwanted parts, and being left with useful mechanical devices. The methods commonly used to remove excess material are wet and dry etching, allowing varying degree of control on the profile of the final structure. Wet etching Wet etching is obtained by immersing the material in a chemical bath that dissolves the surfaces not covered by a protective layer. The main advantages of the technique are that it can be quick, uniform, very selective and cheap. Dry Etching Dry etching is a series of methods where the solid substrate surface is etched by gaseous species. The etching can be conducted physically by ion bombardment (ion etching or sputtering and ion-beam milling), chemically through a chemical reaction occurring at the solid surface (plasma etching or radical etching), or by mechanisms combining both physical and chemical effects (reactive ion etching or RIE)

Surface Micromachining Unlike bulk micromachining in which microstructures are formed by etching

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

into the bulk substrate, surface micromachining builds up structures by adding materials, layer by layer, on the surface of the substrate. The thin film layers are typically 15 µm thick, some acting as structural layer and others as sacrificial layer. Dry etching is usually used to define the shape of the structure layers, and a final wet etching step releases them from the substrate by removing the supporting sacrificial layer. A typical surface micromachining process sequence to build a micro bridge is shown in Figure, Phosphosilicate glass (PSG) is first deposited by LPCVD to form the sacrificial layer. After the PSG layer has been patterned, a structural layer of low-stress polysilicon is added. Then the polysilicon thin-film is patterned with another mask in CF4 + O2 plasma. Finally, the PSG sacrificial layer is etched away by an HF solution and the polysilicon bridge is released.

Basic process sequence of surface micromachining

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

A Surface Micromachined component

LIGA LIGA is a technology which creates small, but relatively high aspect ratio devices using xray lithography. The process typically starts with a sheet of PMMA. The PMMA is covered with a photomask, and then exposed to high energy x-rays. The mask allows parts of the PMMA to be exposed to the x-rays, while protecting other parts. The PMMA is then placed in a suitable etchant to remove the exposed areas, resulting in extremely precise, microscopic mechanical elements. LIGA is a relatively inexpensive fabrication technology, and suitable for applications requiring higher aspect ratio devices than what is achievable in Surface Micromachining.

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

A graphic description of LIGA process

A product of LIGA Micromachining

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

Applications Owing to the batch-mode manufacturing techniques borrowed from the integrated circuit industry, small size die,

and consequently large volumes and lower cost have become possible. These advantages have allowed MEMS devices to displace old products while providing equivalent (or added) functionality. The various applications of BioMEMS devices are shown in the figure below.

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

Cardiovascular Monitoring and Diagnosis Disposable Blood Pressure Sensor – Very low-cost miniature silicon MEMS pressure sensor used in line with IV unit Electronic Stethoscope – Piezoelectric film used as a contact microphone to receive heartbeat and breathing sounds Electronic Stethoscope – Piezoelectric film used as a contact microphone to receive heartbeat and breathing sounds Cardiovascular Treatment Ablation catheter – Force transducer measures precise location of catheter tip during heart ablation to correct arrhythmia Angioplasty Balloon Inflating Pump – Silicon MEMS pressure sensor measures inflation of angioplasty balloon Oxygen Conserver – Piezoelectric film or Silicon MEMS pressure sensor detects inhalation and opens oxygen flow valve Oxygen Tanks – Microfused™ load cells measure remaining oxygen level in tank Patient Monitoring and Diagnosis Bone Density – Piezoelectric film used as an ultrasound transducer to measure bone density Body Fat Scale – Electrodes used to determine body fat through electrical impedance Body Weight – Microfused™ load cell used on a scale for patient weighing Hospital Bed Vital Signs – Piezoelectric film used to measure breathing patterns and heart rate; Microfused™ load cells to monitor patient weight and departure from bed Patient Treatment Ambulatory Infusion Pumps – Si MEMS pressure sensors or Microfused™ load cells used to detect presence and/or rate of flow Bubble and Level Detection – Ultrasonic sensors detect bubbles or medication levels during infusion Hospital Gas Monitoring – Si MEMS pressure sensors detect gas flow for hospital medical gas systems Infusion Pump – Piezoceramic diaphragm used to drive fluid at very slow rates Kidney Dialysis – Microfused™ strain gage pressure sensor used to measure liquid flow pressure Surgical / Delivery

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

Baby Delivery System – Silicon MEMS pressure sensor used to monitor pressure on vacuumassist baby delivery system Body Heat Exchange – Si MEMS very low pressure sensor measures partial vacuum used to expand the blood vessels for quick heat exchange Disposable Digital Display – Low-cost Silicon MEMS pressure sensor with display measures knee pressure during surgery Kidney Transportation – Disposable blood pressure sensors enable flow through organs during transport to extend organ life.

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

CONCLUSION • The BioMEMS devices promises to change the practices in medical field. • The implantable sensors are the most useful • LIGA Micromachining is the best process for Fabrication • The MEMS CAD needs improvements

Department of Mechanical Engineering SDM-CET Dharwad

Bio-MEMS

REFERENCES 1. BioMEMS by Nabiollah Abolfathi 2. Nadim Dale Gee, Kurt E. Petersen, and Gregory T.A.Kovacs, Stanford University, Center for Integrated Systems “Medical Applications of MEMS” 3. Aaron Alexander, Lucas Rogers, Dan Sheehan, Brent Willson, Northwestern University, “Microelectromechanical Drug Delivery Systems” 4. KEITH J. REBELLO, MEMBER, IEEE, Invited Paper, “Applications of MEMS in Surgery” 5. Robert L. Bratter, Cronos Inteyrated Microsystems, “Commercial Success in the MEMS Marketplace” 6. Bala Kashi, Measurement Specialties, “Choosing Sensors for Medical Applications” 7. Sandeep Kumar, Ram P Bajpai, Lalit M Bharadwaj, 2004 IEEE, “Diagnosis Of Tuberculosis Based On BioMEMS” 8. Dennis L. Polla University of Minnesota, 2001 INTERNATIONAL SYMPOSIUM ON MICROMECHATRONICS AND HUMAN SCIENCE, IEEE, “BioMEMS Applications in Medicine” 9. Ronalee Lo, Kenrick Kuwahara, Po-Ying Li, Rajat Agrawal, Mark.S.Humayun, Ellis Meng, University of Southern California “A Passive Refillable Intraocular MEMS Drug Delivery Device”

Department of Mechanical Engineering SDM-CET Dharwad