Touchless Positioning Interface: The Precise Nanosheet Moisture Sensor

The rapid evolution of digital technologies, from smartphones to smart home systems, demands innovative and intuitive touchless control solutions. In this context, humidity sensors are promising candidates for use in smart TPI which operate based on local variations in the humid environment around the human finger. However, the existing devices, such as resistive and capacitive sensors fail to meet the demands for rapid response, high resolution, and sensitivity, especially in applications requiring precise environmental detection or touchless operation. Current technologies often exhibit delays and lack the spatial accuracy required for these tasks. This innovation addresses these gaps by using a nanosheet of active material that enables fine-tuned environmental sensing with fast and reliable responses through changes in its electrical or optical properties, suitable for multiple technological applications, such as smart home technologies and healthcare monitoring.

The core of this invention is a highly sensitive moisture and gas sensor based on 2D nanosheets. These ultra-thin layers change their physical and chemical properties—such as resistivity, size, or refractive index—when exposed to environmental changes. This responsiveness enables precise detection of humidity, gases like CO₂, or solvent vapors.
The sensor uses a vapor-phase amine intercalation process, where amine molecules are inserted between the nanosheet layers (H₃Sb₃P₂O₁₄) (Fig. 1). This technique fine-tunes the interlayer spacing at a sub-Å scale (Däntl et al., 2020), directly impacting the sensor’s sensitivity, polarity, and optical properties. The result is a highly customizable sensor with a response range spanning over five orders of magnitude and a recovery time of just a few seconds.
The planar design allows for integration into compact devices, while its reversible amine exchange process ensures reusability and adaptability for varied applications, from touchless interfaces to environmental monitoring.

• High Sensitivity: Detects environmental changes with remarkable accuracy and sub-centimeter spatial resolution over a wide range.
• Rapid Response: Quick adaptation to environmental fluctuations, with response times in seconds.
• Compact Design: Ultra-thin nanosheets enable integration into various device architectures.
• Versatile Detection: Recognizes specific gases and compounds (e.g., CO₂, solvent vapors) and humidity variations.

• TPIs for digital devices, such as smartphones and tablets.
• Gas detection systems for industrial and environmental monitoring.
• Smart and privacy windows for adaptive transparency and privacy control.
• Wearable Sensors for healthcare and fitness tracking.
• Resistive relative humidity sensors for industrial and consumer applications.

PCT (WO2016102139A1; 26.11.2015), active in EP, US, JP, CN, KR

Däntl, M., et al. “Customizing H3Sb3P2O14 nanosheet sensors by reversible vapor-phase amine intercalation”, Nanoscale Horiz. 5 (2020).

Däntl, M. (2022). Insights into the amine intercalation behavior of layered antimony phosphate thin films and their application in one-dimensional photonic crystals (Doctoral dissertation, lmu).