## 2 Design and Fabrication of the Robot Fingertip Module
The heater had an approximate output of 471 mW at a voltage of 3.3 V. As a result, heat would flow as the module came into contact with an object placed at room temperature, which then enabled the developed temperature sensor to detect temperature changes of the module and measure the inherent thermal conductivity of the object. The artificial skin of the module was designed to possess a stiffness corresponding to the [PERSON]'s modulus range of the index finger (0.07 MPa-0.2 MPa) [28] by using Ecoflex 0030 (Smooth-on Inc., Macungie, PA, USA) [29]. Furthermore, a fingerprinted skin with human-like fingerprints was used to induce vibrations when rubbing the object with the robot fingertip [30]. The robot fingertip module is illustrated in Figure 1c. The implementation of the designed module begins with the fabrication of the multimodal tactile sensor. The fabrication process of the tactile sensor can be subdivided into the fabrication of the sensing layer and the PDMS layers. The initial stages of the sensing layer fabrication process involve the transfer of a doped 100 nm-thick single-crystalline silicon layer from an SOI (Silicon-On-Insulator, SOTEC, Isere, France) wafer to a PI substrate (sensing layer) via a previously reported dry-transfer method. The forms of the U-shaped strain gauges were patterned onto the transferred silicon layer via the photolithography process. Subsequently, etching equipment (ERR-5006, LAT Co., Ltd., Suwon-si, Korea) was used to leave the pattern and etch the remaining parts. To fabricate the electrodes of the strain gauges, deposition equipment (KVE-T2000, Vacuum Tech, Gimpo-si, Korea) was used to deposit a metal layer (Cr: 5.7 nm/Au: 120 nm), and the electrode shape was patterned via the photolithography process. The wet etching method was employed to leave only the electrode shape to fabricate the 3-axis force sensor. Subsequently, the sensing layer was spin-coated using Su-8 2005 (MicroChem Corporation, Westborough, MA, USA) to fabricate an insulating layer that separates the temperature sensor from the 3-axis force sensor. Next, the temperature sensor was fabricated by patterning the shape of the temperature sensor onto the insulating layer via the photolithography process and placing it in the deposition equipment to deposit a metal layer (Cr: 5.7 nm/Au: 120 nm). Once the deposition process was completed, the lift-off process was used to leave only the temperature sensor shape to conclude the sensing layer fabrication process. For the fabrication of the PDMS layers, the encapsulation layer was produced by pouring 5:1 PDMS directly on the completed sensing layer, conducting spin coating, and curing it in an oven (70 \({}^{\circ}\)C) for 2 h. The bump layer was produced by pouring 5:1 PDMS onto a metal mold and curing it in an oven under the same conditions as the encapsulation layer. The fabricated encapsulation and bump layers were then combined via the O\({}_{2}\) plasma treatment process [31; 32]. Next, the deformation layer was fabricated by attaching a PI substrate (adhesion layer) to a wafer coated with 10:1 PDMS, pouring 50:1 PDMS on top of the PI substrate, conducting spin coating, and curing at room temperature (23 \({}^{\circ}\)C) for 24 h. The tactile sensor fabrication process concluded by attaching the PI substrate (sensing layer) combined with the bump layer on top of the produced deformation layer. To attach the fabricated tactile sensor to the fingertip frame, a thin layer of 50:1 PDMS was applied to the section where the sensor is to be located and cured in an oven (70 \({}^{\circ}\)C, 2 h), after which the PI substrate (adhesion layer), the lowest layer of the sensor, was attached to the section. Subsequently, the fingertip frame with the sensor attached was placed in a mold dedicated to the fabrication of fingerprinted skin that was filled with Ecoflex 0030, and the mold was then cured in an oven (70 \({}^{\circ}\)C) for 2 h to produce the fingerprinted skin.