Dr. Peter H.-T. Liu

Accomplished Senior Scientist and Engineer with a distinguished career in experimental fluid mechanics and high-precision, sensor-controlled systems. Recently retired from OMAX Corporation after 17 years as Senior Scientist, now applying deep technical expertise to biomedical engineering and intelligent wearable devices.

Unique dual perspective as both a precision engineer and expert user with firsthand experience managing osteoarthritis, driving innovation in adaptive orthotic technology through the development of an AI-powered "Bilateral Mobility Synchronizer."

Throughout my career, I have established and maintained productive collaborations with leading research institutions and universities worldwide, advancing the frontiers of fluid mechanics, precision manufacturing, and materials science.

Revolutionizing Micro-Scale Manufacturing

Successful development of micro abrasive waterjet (μAWJ) technology for high-precision machining of advanced materials at meso-micro scales. This versatile technology enables machining complex features in most materials including temperature-sensitive ones with minimal thermal damage and high accuracy. For extremely precision parts, it could serve advantageously as a near-net shaping tool to minimize wear of precision tools. Next step is to develop micro Abrasive Slurry Jet (μASJ) toward true micromachining.

Advanced Micro Abrasive Slurry Jet (μASJ) for Precision Micromachining

Leveraging decades of expertise in advancing waterjet technology to develop μASJ for true micromachining for features ~50μm.

Key Innovations

• Develop μASJ technology by direct pumping abrasive slurry through the nozzle
• Innovative system design to ensure reliable operation:
  • Do away the mixing tube of the μAWJ nozzle (reduce the jet diameter by a factor of 2 to 3)
  • No air entrainment in the 2-phase micro slurry jet (reduce jet diameter another factor of up to 2)
  • Enable the use very fine abrasive in the slurry (< 800 mesh) to improve cut quality
• The μASJ is expected to machine features around 50μm, comparable to lasers and wire EDM but without creating heat affected zones (HAZ)
• The cutting power of μASJ is up to five times that of μAWJ for the same hydraulic power

Applications & Impact

• Medical Devices: Precision and real-time machining of patient-specific stents, micro-fluidic devices, and surgical instruments
• Electronics: Dicing of silicon wafers, substrate machining, and micro-electronics packaging
• Aerospace: Machining of turbine blade cooling holes and composite components
• Research & Development: Prototyping of micro-electromechanical systems (MEMS) and lab-on-chip devices

Technical Achievements

• Achieved feature sizes as small as 50μm with tight tolerances (±5μm)
• Developed processes for machining complex 3D micro-structures
• Enhanced surface finish (Ra < 0.5μm) in brittle materials
• Integrated real-time monitoring and adaptive control systems
• Reduced machining costs by 40% compared to laser and EDM processes

Research Leadership

Led multiple NSF SBIR projects focusing on the development of subminiature abrasive-waterjet nozzles and advanced machining processes. Collaborated with leading universities and research institutions to advance the state of the art in micro-scale abrasive jet machining.

The Vision: Bilateral Mobility Synchronizer

Leveraging decades of expertise in precision control systems and sensor integration to develop a revolutionary AI-powered knee brace that addresses the limitations of current orthopedic solutions.

Key Innovations

• Real-time Bilateral Synchronization: Coordinating movement between healthy and affected limbs
• Adaptive Unloading Technology: Dynamic pressure redistribution based on activity
• Predictive Gait Analysis: AI-driven movement anticipation and correction
• Multi-sensor Integration: Combining IMU, force, and biometric sensors

Personal Motivation

Driven by firsthand experience with knee osteoarthritis from tennis, combined with extensive analytical self-study of biomechanical support. This unique perspective bridges the gap between clinical need and engineering execution.

Technical Approach

Applying principles from high-precision waterjet control systems - including real-time sensor feedback, adaptive algorithms, and low-latency response - to create a responsive, natural-feeling assistive device.

Authored two books, several book chapters, and over 80 journal and conference articles

Books & Book Chapters

• Liu, Peter H.-T., Ed. (2024) "Versatility of Waterjet Technology — Multi-Mode Machining of Most Materials from Macro- to Micromachining", Jenny Stanford Publishing (ISBN 9789814968966)
• Liu, H.-T. and Schubert, E. (2012) "Micro Abrasive-Waterjet Technology", in Micromachining Techniques for Fabrication of Micro and Nano Structures
• Liu, Peter H.-T. (2025) "From Raw Cutting to Precision of Machining – A History of Waterjet Technology" Jenny Stanford Publishing.

Recent Journal Articles

• Liu, H.-T. (Peter) and Neil Gershenfeld (2020) "Performance comparison of subtractive and additive machine tools for meso-micro machining," JMMP
• Liu, H.-T. (2019) "Advanced Waterjet Technology for Machining Curved and Layered Structures," Curled and Layer Structure Journal
• Liu, H.-T. (2017) "7M Advantage of Abrasive Waterjet for Machining Advanced Materials," J. Manuf. Mater. Process.

Notable Early Work

• Liu, H.-T., and Lin, J.-T. (1982) "On the Spectra of High-Frequency Wind Waves," Journal of Fluid Mechanics
• Liu, H.-T. (1992) "Effects of Ambient Turbulence on the Decay of a Trailing Vortex Wake," AIAA Journal of Aircraft
• Liu, H.-T. (1995) "Energetics of Grid Turbulence in a Stably Stratified Fluid," Journal of Fluid Mechanics

Selected Patents

• Liu, Peter H.-T. (2010) "Flash Vaporizing Water Jet and Piercing with Flash Vaporization," US Patent No. 7,815,490
• Liu, Peter H.-T. and Hay, K. A. (2015) "Abrasive materials for use in abrasive-jet systems," U.S. Patent No. 9,090,808
• Liu, Peter H.-T. and Schubert, E. (2014) "Piercing and/or cutting devices for abrasive waterjet systems," U.S. Patent No. 8,821,213
• Liu, Peter H.-T. (2014) "Abrasive jet systems utilizing hydrophobic materials," U.S. Patent No. 8,920,213

Proprietary Technologies

• Portable Surface Windshear Alert System (SURFWAS)
• Integrated Stereoscopic Imaging and Measurement (ISIM) method
• Ultrahigh-pressure cryogenic jets and flash waterjets
• PC-based stereoscopic imaging and measurement system (SIMS)
• Micro abrasive waterjet (μAWJ) technology developed under an NSF SBIR grant. Award-winning MicroMAX® was Commercialized for meso-micromachining 2016 R&D 100 Finalist

Knee Brace Project Collaboration

Seeking research partnerships with institutions and individuals in:

• Wearable robotics and exoskeletons
• Biomechanical engineering
• Sensor fusion and AI control systems
• Rehabilitation technology
• Rapid prototyping and manufacturing of components of patient-specific knee braces with advanced waterjets