Body-contouring devices deliver controlled thermal energy to treat cellulite, reduce localized fat, and improve skin elasticity. Since the thermal effect is closely related to the delivered RF output power, precise control of the output power is critical for both efficacy and safety. In this study, we propose a 2.4 GHz CMOS pulse-mode transmitter for body-contouring device applications, featuring precise control of the average power delivered to the body. The transmitter comprises a fully integrated phase-locked loop (PLL) synthesizer, pulse modulator (PM), and 10 mW power amplifier (PA). It is fabricated in a 65 nm CMOS with a compact die area of 3.75 mm². The PA provides four-level continuous-mode output control from −0.3 dBm to 11.1 dBm, and the PM performs programmable PA switching for pulse-mode operation of the PA with a wide range of pulse rates and duty ratios. By combining the continuous-mode output power control and pulse-mode on–off time regulation, the average output power delivered to the skin is finely controlled, managing the delivered power within a safe skin temperature below 65 °C. The PLL loop filter is fully integrated with a wide programmability, improving the form factor and bill of materials for the target devices. Measurement results confirm that the designed transmitter can accurately control both the average output power and pulse profile across the 2.4 GHz ISM band, demonstrating its suitability for compact home-use RF body-contouring devices.

Background/Objectives: Androgenetic alopecia (AGA) is the most prevalent form of hair loss. Although topical minoxidil (MNX) is widely used to treat AGA, its efficacy is limited by poor penetration across the stratum corneum. This study evaluated radiofrequency (RF) microporation as a means of enhancing cutaneous MNX delivery and hair-regrowth efficacy in a dihydrotestosterone (DHT)-induced AGA mouse model. Methods: RF-induced skin permeabilization and barrier recovery were assessed in rats using methylene blue and rhodamine B staining. In vivo skin deposition and pharmacokinetic studies were conducted to quantify cutaneous MNX accumulation and systemic exposure. Hair-regrowth efficacy was evaluated in DHT-treated mice. Results: RF microporation generated transient microchannels in the stratum corneum, increased rhodamine B penetration into deeper skin layers, and allowed substantial barrier recovery within 24 h. RF pretreatment significantly increased MNX deposition in the epidermis/dermis by 2.40-fold at 1 h and 1.94-fold at 3 h compared with topical MNX alone. RF-assisted topical administration resulted in a relative bioavailability of 11.17%, compared with 4.74% for topical administration without RF, while dose-normalized systemic exposure remained substantially lower than that following oral administration. In the AGA model, RF-assisted MNX treatment significantly increased hair coverage, length, and shaft thickness. Histological analysis further showed more prominent follicular structures in the RF-assisted MNX groups. Conclusions: RF microporation creates transient microchannels that enhance cutaneous MNX delivery and improve hair-regrowth efficacy. Importantly, RF-assisted topical administration maintained substantially lower systemic exposure than oral administration, supporting its potential as a needle-free strategy for topical AGA therapy and further translational evaluation.

The authors Kyu-Jin Cho, Jae-Woo Shin, Yun-Seong Eo, Eun-Seong Kim, and Nam-Young Kim were not included as authors in the original publication