Ultrasensitive ionotropic pressure sensor based on biopolymer gel for tactile feedback recognition

Rapidly developing human-machine interface devices and wearable devices require flexible, high-sensitivity, compact and user-friendly designs. Ion-type pressure sensors have the characteristics of high sensitivity and fast response, and are expected to play a key role in the field of virtual reality/augmented reality as tactile feedback.

According to MEMS Consulting, researchers from the Middle East Technical University (METU) have recently developed a cellulose-based supramolecular biopolymer gel (SBPG) with high ionic conductivity and excellent stiffness, which are converted into an ion-type pressure sensor with an ultra-high sensitivity of 1475000 kPa⁻¹. The researchers used eight supramolecular biopolymer gel-based ion-type pressure sensors to prepare a glove prototype. Based on tactile feedback, the smart glove can achieve a classification accuracy of 90% in object recognition, verifying the application potential of the technology. The relevant research results have been published in the journal Vanguard Materials Technologies.

In this work, the researchers found that a dielectric layer with excellent electrochemical properties and high stiffness is a key condition for achieving high performance of ionized pressure sensors. Through extensive chemical and electrochemical characterization, the researchers optimized the design of the dielectric layer of the ionized pressure sensor. The dielectric layer is composed of a supramolecular biopolymer gel based on hydroxyethyl cellulose (HEC), glycerol and sodium chloride (NaCl). The self-assembly of HEC and glycerol molecules is optimized to obtain the highest possible ionic conductivity (9.85 × 10⁻⁴ S/cm) and a surface with sufficient stiffness. This fundamental breakthrough in the sensor dielectric layer makes it possible to prepare industry-leading ultra-sensitive ionized pressure sensors.

Characterization of supramolecular biopolymer gels

The ionized pressure sensor prepared in this research work has unprecedented sensitivity (1475000 kPa⁻¹) and stability, and the peak operating power of the sensor is 4 μW. Under a pressure of 16 kPa, the response and recovery times of the sensor are 63 ms and 35 ms, respectively. Under various cyclic loads of 1 ~ 30 kPa, the sensor exhibits good repeatable capacitive response characteristics. The sensor can successfully resolve micro pressures of 1 ~ 2 Pa and medium pressures of 50 ~ 100 Pa. The mechanical stability and stability of the sensor were verified by compression cycle tests and bending cycle tests. In addition, under different relative humidity conditions, the sensor exhibits a very stable pressure response.

Characterization of Ionization Pressure Sensors

Based on the ionized pressure sensor, the researchers prepared a prototype of a smart glove, demonstrating the ultra-high sensitivity of the sensor. The smart glove is made based on eight sensor units, and the sensors are connected using conductive fibers. The sensors are placed at three key points on the fingertips and palms, and can detect the pressure exerted on these specific areas by the gripped object. The results show that the smart glove can distinguish between objects of similar shape but different sizes and weights by relying on the tactile feedback obtained by the pressure sensor. Due to the unprecedented sensitivity of the ionized pressure sensor, the smart glove can achieve a classification accuracy of 90% using only eight sensor units.

Ionostatic pressure sensor based on supramolecular biopolymer gel for smart gloves

In summary, in this work, the researchers optimized the design of the supramolecular biopolymer gel dielectric layer of the ionotropic pressure sensor through extensive chemical and electrochemical characterization. This design strategy can also be extended to other electrochemical devices, such as batteries and etc., to achieve unprecedented device performance. Based on this optimized supramolecular biopolymer gel dielectric layer, the researchers prepared an ultra-high sensitivity (1475000 kPa⁻¹) ionotropic pressure sensor, which was integrated into a smart glove and can be used to identify objects through tactile feedback. Experiments have shown that the smart glove can achieve high accuracy, precision, and recall using only eight sensors, highlighting the potential of this approach to develop tactile sensing applications in human-computer interaction and robotic environments.

Review editor: Liu Qing