New pressure sensor
A group of researchers from the University of Connecticut has developed a biodegradable piezoelectric pressure sensor that can be useful in clinical practice to track the dynamics of lung diseases, brain edema and other diseases. At the end of use, the sensor is absorbed in the patient's body.
The small flexible sensor is made of materials that are safe for humans, from which suture material for surgical operations, medical implants, bone grafts are made. This distinguishes it from existing sensors that will contain potentially toxic components in their composition. Another difference is that existing analogues cannot decompose inside the human body, they must be removed – that is, additional intervention in the body is required, which is associated with the risk of infectious complications, and also requires a recovery period for the patient.
The new sensor, developed by the Thanh Duc Nguyen group, generates a small electric charge when it experiences pressure. The device can also be used for electrical stimulation of regenerative processes in tissues. In the future, it may be useful for the management of patients with glaucoma, heart disease, bladder cancer.
The prototype of the sensor is made of a thin polymer film with a length of 5 mm, a width of 5 mm and a thickness of 200 microns. It was implanted into the abdominal cavity of a mouse to control the respiratory rate and gave a signal in response to each contraction of the diaphragm for 4 days, after which it disintegrated into organic components.
In order to assess the safety of the sensor, the researchers implanted it on the mouse's back, and then observed the reaction of the animal's immune system. As a result, there was an unexpressed inflammation immediately after implantation; after 4 weeks, the surrounding tissue completely returned to normal.
One of the most difficult tasks of this project was to create a biodegradable material capable of generating an electric pulse in response to pressure or compression – a phenomenon known as the piezoelectric effect. The safe decomposable polymer used to create the sensor consisted of poly-L-lactide (PLLA), which is a neutral material and does not emit electrical impulses in response to pressure.
The researchers were able to modify the PLLA into a piezoelectric material by heating, stretching and cutting strictly at right angles, thus changing its molecular structure.
As a result, the composition of the sensor was as follows: two layers of piezoelectric film PLLA, sandwiched between the smallest molybdenum electrodes and coated on top with a layer of polylactic acid (PLA). Molybdenum is used to create vascular stents and hip prostheses, PLA – for bone screws.
Diagram of the structure of the piezoelectric pressure sensor.
A drawing from an article in PNAS.
Piezoelectric films from PLLA generate weak electrical impulses in response to even the lightest pressure. These pulses are picked up by special receivers, processed and transmitted to the monitor.
To test the concept of the new sensor, the researchers connected it to a signal amplifier located outside the mouse body. The received signal was strong enough to be picked up and recorded by an oscilloscope.
When compared with the sensors already on the market, the new sensor of the Nguyen group was in no way inferior to them and was just as reliable, it captured a wide range of effects characteristic of the physiology of the brain, eyes and abdominal cavity.
The sensitivity of the sensor can be adjusted by changing the number of layers of PLLA film and in other ways.
Currently, the group is busy extending the service life of the sensor. The ultimate goal is to create a product that can completely dissolve in the body.
The research group has applied for a patent for their invention. The application is under consideration.
Article by Eli J. Curry et al. Biodegradable Piezoelectric Force Sensor is published in the journal PNAS.
Aminat Adzhieva, portal "Eternal Youth" http://vechnayamolodost.ru