What are sensors?

In medicine and biotechnology, sensors are tools that detect specific biological, chemical, or physical processes and then transmit or report this data. Some sensors work outside the body while others are designed to be implanted within the body.

Some monitoring devices consist of multiple sensors that measure a number of physical or biological parameters. Other devices may be multifunctional, incorporating sensors and then delivering a drug or intervention based on the sensor data obtained. Sensors may also be components in systems that process clinical samples, such as increasingly common “lab-on-a-chip” devices.

The use of devices which use detector molecules to detect, investigate, or analyze other molecules, macromolecules, molecular aggregates, or organisms.

How are sensors used in current medical practice?

Many different types of sensorsare already used in health care, including self-care at home. Thermometers translate the expansion of a fluid or bending of a metal strip in response to heat into a number corresponding to body temperature. Paper-based home pregnancy tests contain a substance that changes color in the presence of hormones indicating pregnancy. In hospitals and other provider-based settings, you can find more complex types of sensors like pulse oximeters (also known as blood-oxygen monitors), which measure changes in the body’s absorption of special types of light to provide information on a patient’s heart rate and the amount of oxygen in the blood.

How might novel sensors improve medical care or biomedical research?

Advances in technology, engineering, and materials science have opened the door for increasingly sophisticated sensors to be used in medical research. A group of NIBIB-funded researchers developed a compact, wireless, implantable brain sensor that can record and transmit brain activity data. Building on previously developed brain-computer interfaces that used wired connections, this new sensor may someday lead to unobtrusive, thought-controlled prosthetics and other assistive devices for people with amputated limbs, paralysis, or other movement impairments.

Researchers at NIBIB aim to improve existing sensors through a variety of means, such as making fluorescent probes easier to see and increasing the capabilities and enhancing efficiency of individual sensors.

Some scientists are exploring biological sensors, which rely on substances that occur naturally in the body, or artificial compounds that mimic natural substances, to capture molecules that are important to measure in the body. Biosensors may provide insights into disease processes that are hard to detect directly, such as dysfunctions in brain chemistry that are thought to play a role in many mental disorders.

For example, one method for studying chemical processes in real-time uses engineered cells that can be “programmed” with receptors that latch onto specific brain chemicals. The resulting chain of activity causes a protein within the cell to change color that researchers can detect with a certain type of laser microscope. The biosensors remain active in the brain for several days, allowing scientists to study changes in brain chemistry over time, which may help inform efforts to improve drug treatments for mental disorders.

While many advanced sensors aren’t practical for routine medical care, they allow researchers to study the basic foundations of disease in more detail than previously possible, and to develop new technologies that could dramatically improve the quality of life of people with severe disabilities.

What technologies are NIBIB-funded researchers developing with sensors?

Sensors play key roles in all aspects of health care—prevention, diagnosis, disease monitoring, treatment monitoring—and the range of research involving sensors is equally broad. In addition to health-related applications, NIBIB funds studies to test new materials and technologies for building sensors, to develop new sensors that can advance medical research, and to promote healthy independent living through home-based and wearable sensors.

New Materials & Technologies

Good health requires not only protecting our bodies but safeguarding things we put into our bodies as well. NIBIB-funded researchers developed a sensor using a thin membrane made from of a special kind of plastic. The researchers loaded the membrane with a compound that creates a voltage difference across the membrane in the presence of OSCS, a potentially deadly contaminant sometimes found in preparations of the commonly used blood thinner heparin. OSCS is inherently highly charged and interacts with the compound-loaded membrane without the need to apply an external electrical current. By measuring the voltage, scientists can quickly identify OSCS-contaminated samples before the heparin is administered to a patient. The reaction between OSCS and the membrane is also reversible, so the sensors can be used repeatedly.

Another NIBIB grant supported research to develop an instrument to detect and monitor levels of vapor phase hydrogen peroxide (VPHP). VPHP is much stronger than the type of hydrogen peroxide commonly used in first aid care but has a similar use: to disinfect and sterilize pharmaceutical manufacturing equipment and facilities. After sterilization procedures, manufacturers have to ensure VPHP levels are reduced back to a minimum to protect workers and product quality. The researchers developed a sensor that uses a new type of highly efficient and extremely sensitive laser to continuously monitor VPHP levels throughout the sterilization process. The sensor can also detect how much VPHP has been absorbed by packaging and other materials within the facility, such as sterile isolators or other protective barriers.

Advancing Medical Research

Many illnesses develop and progress as a result of faulty regulation or dysfunction of a range of hormones, neurotransmitters, or other important body chemicals. Tracking such chemical activity is key to unraveling disease processes, but current sensors are generally limited in the number of chemicals that can be analyzed at one time or require those chemicals to be labeled first, thus greatly increasing the time, cost, and complexity of sensing. NIBIB-funded researchers seek to improve on biosensors in a variety of ways, such as creating novel types of coatings that improve sensor sensitivity, selectivity, and stability; and developing a fluorescence-based strategy for detecting proteins in living organisms and in real time.

Healthy Independent LivingEnvironmental and mobile sensors are already a part of many people’s everyday lives. For example, faucets that automatically start when you place your hands under them and shut off when you’re done washing. Lights that turn themselves on when you enter a room. Wearable bands that track your daily activity, perhaps even coordinating with your smartphone to allow you to track data over time or share your information with others. NIBIB supports initiatives to develop improved sensor and related information technologies for home and mobile use that will sustain wellness and facilitate coordinated management of chronic diseases. For example, one research team is working to improve the ability of “smart homes” to make sense of real-time sensor data and to recognize changes in a resident’s activity patterns that may signal changes in well-being, such as a fall or disrupted meal schedule.

What are important areas for future research on sensors?

The types of sensors being developed and studied currently may play key roles in expanding and greatly changing the delivery of health care. One area in particular that may benefit from sensor research is point-of-care (POC) technologies.

Point-of-care refers to the place where patients receive health care, which may be anywhere from primary care offices or community clinics to emergency rooms or even patients’ own homes. POC research seeks to address barriers to health care that have arisen from the concentration of services in highly specialized medical centers and labs. POC technologies may allow providers to diagnose and treat a particular health condition in a single visit, so patients don’t need to make additional appointments or wait for test results.

Besides funding studies seeking to improve the manufacturing process for low-cost POC technologies, NIBIB-funded efforts are already underway to develop cost-effective POC solutions for detecting a range of medical conditions, including H5N1 influenza and allergies and other autoimmune diseases. Miniature, implantable sensors could continuously monitor a person’s health status, providing more accurate information than conventional disease screening and a clearer sense of when a doctor’s visit is needed. Integrating compact, wireless sensing technologies into medical devices or chronic treatments like long-term oxygen therapy may help lower treatment costs and be easier for patients to use. Such technologies may also be compatible with mobile devices, allowing for remote monitoring and assessments in real-time.

Some of the challenges to sensor research include simplifying and automating the preparation of patient samples to be used at the point-of-care and overcoming the body’s natural rejection response to implantable or minimally invasive sensors.

Your body alerts you to many aspects of your health. Your stomach growling tells you when to eat. A powerful yawn lets you know you’re tired. Your body gives off many other valuable signals, but requires technology to detect them. Scientists are looking for new ways to track and use your body’s signals to improve your health and manage disease.

Physical activity trackers and step counters are now helping people develop and maintain healthy habits. These devices have also opened doors for people to participate in health research. Now, researchers are designing more advanced devices called biosensors that measure biological, chemical, and physical signs of health.

“The variety of biosensors used by researchers, clinicians, and people from every walk of life is growing,” says Dr. Šeila Selimović, a biosensors expert at NIH. “Some speed up test results so treatments can be started promptly. Others provide the benefits of continuous monitoring of health conditions. [Biosensors] function in fascinating ways. [They use] chemical attraction, electrical currents, light-detection systems, and compact wireless-sensing technologies.”

The mercury thermometer is one of the earliest biosensor technologies used in medicine. In modern thermometers, mercury has been replaced by safer temperature-sensitive probes. But the goal is still the same: to detect changes in your body temperature.

Another common biosensor used at home is the pregnancy test. Home pregnancy tests use color-changing strips to detect pregnancy hormones in urine. Pregnancy tests are still done in doctor’s offices. But the home test has become a reliable alternative since it was first introduced more than 40 years ago.

The rapid strep test is another commonly used biosensor. If you have a sore throat, your doctor may want to use one to test for bacteria called streptococci. The rapid strep test can provide results from a swab of the back of your throat in a few minutes—with 95% accuracy. Your doctor may still send a throat swab to a lab to confirm a positive test result. But they can use the rapid test results to start treatment immediately.

In parts of the world where public health care isn’t readily available, researchers hope to introduce rapid tests for people living in remote regions to test for infections like influenza, HIV, and hepatitis C. New biosensor technologies can now be combined with smart phone cameras and wireless signaling. These advances make health tests more portable and affordable than lab-based equipment.

Biosensors can also be used to continuously monitor a health condition. Blood-oxygen monitors are now found throughout hospitals and in patients’ homes. These devices detect changes in the level of oxygen in the bloodstream. A rapid drop in oxygen can cause brain injury and requires quick medical attention. Blood oxygen monitors are ideal for people with lung and heart conditions, those undergoing anesthesia, or those being treated in intensive, neonatal, or emergency care. Other biosensors can be used to continuously monitor your blood sugar levels (for managing diabetes), blood pressure, or heart rate.

Flexible sensors are making even more types of monitoring possible. A team of engineers, led by Dr. Patrick Mercier and Dr. Joseph Wang at the University of California San Diego, is developing a flexible sensor that measures blood alcohol levels. It looks like a temporary tattoo. The sensor releases a sweat-promoting chemical into the skin and detects alcohol in the sweat. The sensor then sends the information wirelessly to a laptop or mobile device. Similar devices are being developed by other groups to monitor cystic fibrosis and other diseases and conditions.

At the University of Minnesota, a group of researchers led by Dr. Michael McAlpine has developed inks for 3-D printing sensors that are flexible, stretchable, and sensitive. These sensors can be used to detect human movements, such as flexing a finger. They can be printed directly onto skin and used to detect body signals, like a pulse. They can also detect chemicals in the environment and be used to warn of hazards.

NIH also supports research to use sensors to gather data about environmental and other factors involved in childhood asthma. These sensor systems monitor what children are exposed to and their body’s reactions. For example, Dr. Zhenyu Li, a biomedical engineer at George Washington University, is developing a sensor that can be worn on a child’s wrist to detect formaldehyde, an air pollutant that can trigger asthma.

“Researchers don’t have tools at the moment that can monitor environmental triggers, physiological responses, and behavior without interrupting normal activities,” Li says. There are many different asthma triggers, he explains. He expects to have a wearable sensor prototype that he and his clinical partners can begin testing with patients. He’s also working on a device that can be placed in a child’s home to detect multiple air pollutants, like those found in tobacco smoke and some manufactured wood products, such as flooring and furniture.

Biosensors can be placed inside your body as well. Dr. Natalie Wisniewski, a biomedical engineer at a medical device company in San Francisco called Profusa, is developing miniature sensors that can be injected under the skin. These sensors automatically track chemicals in your body without drawing blood. They continuously scan multiple factors at once. Normally, you need to stay in a hospital to have your body chemistry continuously monitored. With this technology, information about the chemicals in your body could be accessed around the clock, from anywhere.

Once placed under the skin, such biosensors can last for months to years. They can monitor various body functions through chemical changes. All this information can be collected on a cell phone app and shared with your physician, a caretaker, or anyone else you choose.

“Health sensors have the potential to dramatically improve the way we practice medicine and shift the focus away from reactive treatments to preventive maintenance,” Wisniewski explains.

Biosensors are quickly becoming part of our normal health care routines. New sensor technologies are opening avenues to better health. Researchers are working to develop the biosensors of tomorrow. These could provide access to better health in ways we can’t yet imagine.

Biosensors of Today

Biosensors are already used for many health issues. They can:

• continuously detect your blood pressure without a blood pressure cuff
• help a person with diabetes maintain safe blood sugar levels without a finger prick
• advise a doctor on whether to start a patient on an antibiotic treatment for strep throat
• tell whether a woman is pregnant
• record the levels of oxygen in a patient’s blood without a lab test
• sense the amount of alcohol in a person’s system from their skin
• diagnose patients in low-resource areas that don’t have lab facilities