The Internet of Things (IoT) substantially opened up the need for flexible sensors. Whether a doctor wants to track a patient’s health or an engineer wants to create an improved version of a robotic component, those are two of the many reasons why flexible sensors may emerge as the best options. It’s even better that such sensors are often printable, thereby facilitating fast, consistent production. Here, Megan R. Nichols discusses five fascinating ways to use printed and flexible sensors:
1. Human Movement Optimisation
As anyone who has ever trained for a marathon or attended physical therapy sessions to recover from an injury likely knows well, performing and maintaining the proper movements can be crucial. A German organisation called Fraunhofer ISC responded by creating a printed sensor to incorporate into smart clothing or other wearables, such as fabric braces. After creating the sensor for clothes, the next step is to apply it to a garment with screen printing.
Besides tracking sequences of movement, these printed sensors also recognise pressure. If scientists incorporated this technology into a sock, a coach could verify an athlete bears too much weight on a part of their foot when holding a pose or standing at the starting gate before a race.
2. Brain Aneurysm Monitoring
Since a brain aneurysm becomes a medical emergency once it ruptures, careful monitoring is essential. Many patients diagnosed with them do not experience associated symptoms before the aneurysm bursts, making many physicians opt to take a wait-and-see approach before intervening.
A team at Georgia Tech recently depended on aerosol jet 3D printing to create a stretchable and battery-free sensor. They can use a catheter to wrap it around stents or diverters that medical specialists implant to control the blood flow in affected vessels. The current process of gauging an aneurysm’s severity requires patients to go through angiograms and face exposure to dyes that can cause side effects. This new sensor-based approach could prove less invasive.
3. Robotic Arms
Many robotic arms are pneumatic — air-controlled — systems. The actuators within a robotic arm use the air from a compressor to perform an action, such as movement. Most of these appendages have several actuators in various sections, such as the elbow, wrist and forearm. Robotics engineers can then control each actuator individually for better precision.
Soft robotic actuators are becoming more popular due to their diverse applications and safety. Past projects featuring those components included a soft assistive glove for people to wear while going through hand rehabilitation and a robotic gripper that took samples of fragile underwater species.
Researchers developed a printable, sensor-equipped soft and bendable actuator. It provides bending feedback, plus detects when the arm contacts an object. The team believes their achievement will lead to better results for controlled soft gripping applications, plus non-robotic uses — including wearable devices.
4. Food Packaging
Many people observe the “best by” date on food packaging and discard the item immediately after. The product may still be safe to eat, but individuals don’t want to get an upset stomach — or worse — by finding out. Dr. Sina Naficy wants that to change. He’s designing printable gas sensors made with flexible, conductive inks. They could give a more accurate picture of whether to eat the food or throw it out. 
Naficy envisions applying the sensors with a standard inkjet printer, helping manufacturers quickly start using them in their packages. Certain gases, such as carbon dioxide and ammonia, give clues about food quality. If a container had a sensor to detect such emissions, people could feel more confident about eating some foods that are slightly out of date rather than getting rid of them.
5. Wristbands and Insoles
Engineers who build flexible sensors often struggle to make them sufficiently durable. Thus, fragility limits the potential uses and may make ongoing, long-term applications impossible.
However, collaborators from multiple educational institutions worked on a project at the University of Waterloo that could result in some impressive progress. The team members combined nanotechnology with 3D printing to make a silicone rubber sensor with embedded graphene to create electrical signals.
The researchers confirmed 3D printing enabled creation of the sensor’s honeycomb-like structure, as well as its intricate inner workings. They also discussed how silicone’s flexible and strong characteristics made the sensor suitable for wearable products — including those tolerant of humid or high-temperature environments.
Those who worked on the project brought up wristbands and insoles as two possible applications. Such items may encourage people to exercise or measure their daily activity. However, the developers said the uses don’t stop there.
The 3D printing process allows creating custom devices to fit users’ varied body shapes. A doctor could use these sensors along with other electronic parts to remotely track someone’s vital signs as they recover from an operation. And, since these new sensors withstand the washing machine, they work for clothing, too.
Developments in Printed, Flexible Sensors
This overview shows the incredible potential of printable and flexible sensors. The examples here reveal some of the most beneficial ways to use them and encourage people to ponder what the future might hold.
Megan R. Nichols is a technical writer and blogger. She regularly contributes manufacturing and supply articles to sites like Industry Week, Manufacturing & Logistics IT, and EBN Online. You can follow Megan by subscribing to her blog, Schooled By Science.
